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Sharding with MariaDB MaxScale

Shinguz - Tue, 2024-03-19 17:02
Table of contents
Overview

This feature should more or less work with MariaDB MaxScale 6.x.y, 22.08.x, 23.02.x, 23.08.x and 24.02.x. We have tested it with the latest MaxScale version 23.08.05, as we encountered problems with an older version (MXS-5026).

shell> maxscale --version MaxScale 23.08.5

We used MariaDB 10.11 as the database backend (shards).

Less than approx. 2% of all MariaDB installations known to us are what we technically understand by multi-tenant systems (each customer in its own database (also called a schema)).

This MariaDB MaxScale feature is therefore used relatively rarely and there is an increased risk of encountering bugs that no-one has come across before!

This feature is called SchemaRouter at MariadDB MaxScale and is still declared as beta quality (MXS-5025):

maxctrl> show module schemarouter ┌─────────────┬────────────────────────────────────────────────┐ │ Module │ schemarouter │ ├─────────────┼────────────────────────────────────────────────┤ │ Type │ Router │ ├─────────────┼────────────────────────────────────────────────┤ │ Version │ V1.0.0 │ ├─────────────┼────────────────────────────────────────────────┤ │ Maturity │ Beta │ ├─────────────┼────────────────────────────────────────────────┤ │ Description │ A database sharding router for simple sharding │ ├─────────────┼────────────────────────────────────────────────┤ │ ...

The target topology should look like this: Each customer (client, tenant) is located in its own database (= schema). The databases are distributed across several MariaDB instances (shards). So that the application can access the database transparently, a pair of MaxScale load balancers is connected in front of it, which knows where the customer is located and forwards the traffic to the shard accordingly. To ensure that the MaxScale load balancers are designed for high availability, a virtual IP (VIP) is connected upstream, e.g. using Keepalived. If this is still too simple for you, you can design each individual shard as a master/slave or Galera cluster construct...


Preparation of the shards (MariaDB database instances)

The first problem we had with this PoC was with the test database. By deleting the test database on all shards, the problem disappeared. Alternatively, you can run mariadb-secure-installation, which you should do on production systems anyway, or you can use the MaxScale configuration parameters: ignore_tables or ignore_tables_regex to allow the same tables in different shards (MXS-5027).

See also: MaxScale Router Parameters.

Create test data

So that we have something to play with, we have created test data:

-- On shard 1: 2 customers SQL> CREATE DATABASE customer_0010; SQL> CREATE TABLE customer_0010.address (id INT UNSIGNED, name VARCHAR(255)); SQL> CREATE TABLE customer_0010.sales (id INT UNSIGNED, product VARCHAR(255), sales TINYINT, amount DECIMAL(6, 2), total_amount DECIMAL(6, 2)); SQL> INSERT INTO customer_0010.address VALUES (1, 'Customer 10 GmbH'); SQL> INSERT INTO customer_0010.sales VALUES (1, 'Apples', 5, 1.2, 6), (2, 'Pears', 2, 0.9, 1.8), (3, 'Bread', 1, 2.5, 2.5); SQL> CREATE DATABASE customer_0011; SQL> CREATE TABLE customer_0011.address (id INT UNSIGNED, name VARCHAR(255)); SQL> CREATE TABLE customer_0011.sales (id INT UNSIGNED, product VARCHAR(255), sales TINYINT, amount DECIMAL(6, 2), total_amount DECIMAL(6, 2)); SQL> INSERT INTO customer_0011.address VALUES (1, 'Customer 11 SE'); SQL> INSERT INTO customer_0011.sales VALUES (1, 'Oranges', 2, 1.7, 3.4), (2, 'Salad', 5, 1.2, 6); -- On shard 2: 3 customers SQL> CREATE DATABASE customer_0020; SQL> CREATE TABLE customer_0020.address (id INT UNSIGNED, name VARCHAR(255)); SQL> CREATE TABLE customer_0020.sales (id INT UNSIGNED, product VARCHAR(255), sales TINYINT, amount DECIMAL(6, 2), total_amount DECIMAL(6, 2)); SQL> INSERT INTO customer_0020.address VALUES (1, 'Customer 20 AG'); SQL> INSERT INTO customer_0020.sales VALUES (1, 'Oranges', 2, 1.7, 3.4), (2, 'Salad', 5, 1.2, 6); SQL> CREATE DATABASE customer_0021; SQL> CREATE TABLE customer_0021.address (id INT UNSIGNED, name VARCHAR(255)); SQL> CREATE TABLE customer_0021.sales (id INT UNSIGNED, product VARCHAR(255), sales TINYINT, amount DECIMAL(6, 2), total_amount DECIMAL(6, 2)); SQL> INSERT INTO customer_0021.address VALUES (1, 'Customer 21 GmbH'); SQL> INSERT INTO customer_0021.sales VALUES (1, 'Oranges', 2, 1.7, 3.4), (2, 'Salad', 5, 1.2, 6); SQL> CREATE DATABASE customer_0022; SQL> CREATE TABLE customer_0022.address (id INT UNSIGNED, name VARCHAR(255)); SQL> CREATE TABLE customer_0022.sales (id INT UNSIGNED, product VARCHAR(255), sales TINYINT, amount DECIMAL(6, 2), total_amount DECIMAL(6, 2)); SQL> INSERT INTO customer_0022.address VALUES (1, 'Customer 22 Gebr.'); SQL> INSERT INTO customer_0022.sales VALUES (1, 'Oranges', 2, 1.7, 3.4), (2, 'Salad', 5, 1.2, 6); -- On shard 3: 1 customer SQL> CREATE DATABASE customer_0030; SQL> CREATE TABLE customer_0030.address (id INT UNSIGNED, name VARCHAR(255)); SQL> CREATE TABLE customer_0030.sales (id INT UNSIGNED, product VARCHAR(255), sales TINYINT, amount DECIMAL(6, 2), total_amount DECIMAL(6, 2)); SQL> INSERT INTO customer_0030.address VALUES (1, 'Customer 30 GmbH'); SQL> INSERT INTO customer_0030.sales VALUES (1, 'Pickles', 2, 2.2, 4.4), (2, 'Salad', 1, 3.1, 3.1), (3, 'Pudding', 5, 2.2, 11.0), (4, 'Asparagus', 12, .3, 3.6);
Create roles and users

Since in a sharded system, in contrast to a Galera cluster for example, the individual database instances do not know anything about each other and do not communicate with each other, we have to create the roles and users or accounts individually on EACH shard.

MariaDB MaxScale needs a user for the SchemaRouter service and the monitor (on each shard).

As the name suggests, the monitor user is responsible for monitoring and the SchemaRouter service user is responsible for collecting the user account information from the sharding backends and forwarding the queries to the correct shard.

Since a redundant system typically works with at least two MaxScale routers and we wanted to prevent the privileges of the accounts from diverging, we work with roles for both the MaxScale users and the application users.

MaxScale Monitor User SQL> CREATE ROLE maxscale_monitor_role; SQL> GRANT SELECT ON mysql.user TO 'maxscale_monitor_role'; SQL> GRANT REPLICATION CLIENT ON *.* TO 'maxscale_monitor_role'; SQL> GRANT SLAVE MONITOR ON *.* TO 'maxscale_monitor_role'; SQL> GRANT FILE ON *.* TO 'maxscale_monitor_role'; SQL> GRANT CONNECTION ADMIN ON *.* TO 'maxscale_monitor_role'; SQL> SHOW GRANTS FOR maxscale_monitor_role; +-----------------------------------------------------------------------------------------------+ | Grants for maxscale_monitor_role | +-----------------------------------------------------------------------------------------------+ | GRANT FILE, BINLOG MONITOR, CONNECTION ADMIN, SLAVE MONITOR ON *.* TO `maxscale_monitor_role` | | GRANT SELECT ON `mysql`.`user` TO `maxscale_monitor_role` | +-----------------------------------------------------------------------------------------------+ SQL> CREATE USER maxscale_monitor@'10.139.158.210' IDENTIFIED BY 'secret'; SQL> CREATE USER maxscale_monitor@'10.139.158.211' IDENTIFIED BY 'secret'; SQL> GRANT maxscale_monitor_role TO maxscale_monitor@'10.139.158.210'; SQL> GRANT maxscale_monitor_role TO maxscale_monitor@'10.139.158.211'; SQL> SET DEFAULT ROLE maxscale_monitor_role FOR maxscale_monitor@'10.139.158.210'; SQL> SET DEFAULT ROLE maxscale_monitor_role FOR maxscale_monitor@'10.139.158.211'; SQL> SELECT user, host, is_role, default_role FROM mysql.user WHERE user LIKE 'maxscale_monitor%'; +-----------------------+----------------+---------+-----------------------+ | User | Host | is_role | default_role | +-----------------------+----------------+---------+-----------------------+ | maxscale_monitor_role | | Y | | | maxscale_monitor | 10.139.158.210 | N | maxscale_monitor_role | | maxscale_monitor | 10.139.158.211 | N | maxscale_monitor_role | +-----------------------+----------------+---------+-----------------------+ SQL> SHOW GRANTS FOR maxscale_monitor@'10.139.158.211'; +------------------------------------------------------------------------------------------------------------------------------+ | Grants for maxscale_monitor@10.139.158.211 | +------------------------------------------------------------------------------------------------------------------------------+ | GRANT `maxscale_monitor_role` TO `maxscale_monitor`@`10.139.158.211` | | GRANT USAGE ON *.* TO `maxscale_monitor`@`10.139.158.211` IDENTIFIED BY PASSWORD '*14E65567ABDB5135D0CFD9A70B3032C179A49EE7' | | SET DEFAULT ROLE `maxscale_monitor_role` FOR `maxscale_monitor`@`10.139.158.211` | +------------------------------------------------------------------------------------------------------------------------------+
MaxScale Admin User SQL> CREATE ROLE maxscale_admin_role; SQL> GRANT SHOW DATABASES ON *.* TO 'maxscale_admin_role'; SQL> GRANT SELECT ON mysql.user TO 'maxscale_admin_role'; SQL> GRANT SELECT ON mysql.db TO 'maxscale_admin_role'; SQL> GRANT SELECT ON mysql.tables_priv TO 'maxscale_admin_role'; SQL> GRANT SELECT ON mysql.columns_priv TO 'maxscale_admin_role'; SQL> GRANT SELECT ON mysql.proxies_priv TO 'maxscale_admin_role'; SQL> GRANT SELECT ON mysql.roles_mapping TO 'maxscale_admin_role'; SQL> GRANT SELECT ON mysql.procs_priv TO 'maxscale_admin_role'; SQL> SHOW GRANTS FOR maxscale_admin_role; +------------------------------------------------------------------+ | Grants for maxscale_admin_role | +------------------------------------------------------------------+ | GRANT USAGE ON *.* TO `maxscale_admin_role` | | GRANT SELECT ON `mysql`.`user` TO `maxscale_admin_role` | | GRANT SELECT ON `mysql`.`roles_mapping` TO `maxscale_admin_role` | | GRANT SELECT ON `mysql`.`tables_priv` TO `maxscale_admin_role` | | GRANT SELECT ON `mysql`.`procs_priv` TO `maxscale_admin_role` | | GRANT SELECT ON `mysql`.`db` TO `maxscale_admin_role` | | GRANT SELECT ON `mysql`.`columns_priv` TO `maxscale_admin_role` | | GRANT SELECT ON `mysql`.`proxies_priv` TO `maxscale_admin_role` | +------------------------------------------------------------------+ SQL> CREATE USER maxscale_admin@'10.139.158.210' IDENTIFIED BY 'secret'; SQL> CREATE USER maxscale_admin@'10.139.158.211' IDENTIFIED BY 'secret'; SQL> GRANT maxscale_admin_role TO maxscale_admin@'10.139.158.210'; SQL> GRANT maxscale_admin_role TO maxscale_admin@'10.139.158.211'; SQL> SET DEFAULT ROLE maxscale_admin_role FOR maxscale_admin@'10.139.158.210'; SQL> SET DEFAULT ROLE maxscale_admin_role FOR maxscale_admin@'10.139.158.211'; SQL> SELECT user, host, is_role, default_role FROM mysql.user WHERE user LIKE 'maxscale_admin%'; +---------------------+----------------+---------+---------------------+ | User | Host | is_role | default_role | +---------------------+----------------+---------+---------------------+ | maxscale_admin_role | | Y | | | maxscale_admin | 10.139.158.210 | N | maxscale_admin_role | | maxscale_admin | 10.139.158.211 | N | maxscale_admin_role | +---------------------+----------------+---------+---------------------+ SQL> SHOW GRANTS FOR maxscale_admin@'10.139.158.211'; +----------------------------------------------------------------------------------------------------------------------------+ | Grants for maxscale_admin@10.139.158.211 | +----------------------------------------------------------------------------------------------------------------------------+ | GRANT `maxscale_admin_role` TO `maxscale_admin`@`10.139.158.211` | | GRANT USAGE ON *.* TO `maxscale_admin`@`10.139.158.211` IDENTIFIED BY PASSWORD '*14E65567ABDB5135D0CFD9A70B3032C179A49EE7' | | SET DEFAULT ROLE `maxscale_admin_role` FOR `maxscale_admin`@`10.139.158.211` | +----------------------------------------------------------------------------------------------------------------------------+

See also: SchemaRouter Configuration

Create application role and accounts

The application also requires a user, which we create here as on every shard as follows:

SQL> CREATE ROLE app_role; SQL> GRANT SELECT, INSERT, UPDATE, DELETE ON `customer_%`.* TO 'app_role'; SQL> GRANT SHOW DATABASES ON *.* TO 'app_role'; SQL> GRANT CREATE, DROP, ALTER ON *.* TO 'app_role'; -- For creating new tenant databases SQL> SHOW GRANTS FOR app_role; +----------------------------------------------------------------------+ | Grants for app_role | +----------------------------------------------------------------------+ | GRANT SHOW DATABASES ON *.* TO `app_role` | | GRANT SELECT, INSERT, UPDATE, DELETE ON `customer_%`.* TO `app_role` | +----------------------------------------------------------------------+ SQL> CREATE USER app@'10.139.158.%' IDENTIFIED BY 'secret'; SQL> GRANT app_role TO app@'10.139.158.%'; SQL> SET DEFAULT ROLE app_role FOR app@'10.139.158.%'; SQL> SELECT user, host, is_role, default_role FROM mysql.user WHERE user LIKE 'app%'; +----------+--------------+---------+--------------+ | User | Host | is_role | default_role | +----------+--------------+---------+--------------+ | app_role | | Y | | | app | 10.139.158.% | N | app_role | +----------+--------------+---------+--------------+ SQL> SHOW GRANTS FOR app@'10.139.158.%'; +---------------------------------------------------------------------------------------------------------------+ | Grants for app@10.139.158.% | +---------------------------------------------------------------------------------------------------------------+ | GRANT `app_role` TO `app`@`10.139.158.%` | | GRANT USAGE ON *.* TO `app`@`10.139.158.%` IDENTIFIED BY PASSWORD '*14E65567ABDB5135D0CFD9A70B3032C179A49EE7' | | SET DEFAULT ROLE `app_role` FOR `app`@`10.139.158.%` | +---------------------------------------------------------------------------------------------------------------+
Proxy protocol

Load balancers and proxies have the property that they exchange the IP addresses of the clients with their own IP addresses. On the one hand, this means that you can no longer see where the client originally came from in the database and, on the other hand, you can no longer assign access authorisations to users and IPs, as the IP of the load balancer is always checked.

These two problems can be solved using the proxy protocol.

To do this, both the database and the load balancer, in this case MaxScale, must have the proxy protocol activated.

On the database side, the proxy protocol is activated as follows:

# # my.cnf # [mariadbd] proxy_protocol_networks = ::1, 10.139.158.0/24, localhost

and on the MaxScale side with:

# # /etc/maxscale.cnf # [shard] type = server proxy_protocol = true

You can check the two settings with:

SQL> SHOW GLOBAL VARIABLES LIKE 'proxy%'; +-------------------------+---------------------------------+ | Variable_name | Value | +-------------------------+---------------------------------+ | proxy_protocol_networks | ::1, 10.139.158.0/24, localhost | +-------------------------+---------------------------------+ shell> maxctrl show server shard1 | grep proxy │ │ "proxy_protocol": true, │

Sources:


MaxScale SchemaRouter configuration

Next, we prepare the MaxScale configuration for sharding. The file recommended by MariaDB is /etc/maxscale.cnf. Whether it makes more sense to create a separate configuration file under /etc/maxscale.cnf.d/ or even to configure the entire MaxScale dynamically (/var/lib/maxscale/maxscale.cnf.d/*.cnf) remains to be seen in the long term. See also warnings below. The configuration file for this sharding PoC looks like this:

# # /etc/maxscale.cnf # [maxscale] threads = auto admin_gui = false [shard1] type = server address = 10.139.158.1 port = 3363 proxy_protocol = true [shard2] type=server address=10.139.158.1 port=3364 proxy_protocol = true [shard3] type = server address = 10.139.158.1 port = 3365 proxy_protocol = true [sharding monitor] type = monitor module = galeramon servers = shard1,shard2,shard3 user = maxscale_monitor password = secret monitor_interval = 1s [Sharded-Service-Listener] type = listener service = Sharded-Service protocol = MariaDBClient port = 3306 [Sharded-Service] type = service router = schemarouter servers = shard1,shard2,shard3 user = maxscale_admin password = secret auth_all_servers = true

Note: Recommendation of the MaxScale developer: "One workaround might be to actually use galeramon to monitor the nodes instead of mariadbmon."

Starting and stopping the MaxScale Load Balancer

MaxScale is started and stopped as usual via SystemD:

shell> systemctl restart maxscale shell> systemctl status maxscale ● maxscale.service - MariaDB MaxScale Database Proxy Loaded: loaded (/lib/systemd/system/maxscale.service; enabled; vendor preset: enabled) Drop-In: /run/systemd/system/service.d └─zzz-lxc-service.conf Active: active (running) since Tue 2024-02-27 09:52:57 UTC; 39s ago Process: 187 ExecStart=/usr/bin/maxscale (code=exited, status=0/SUCCESS) Main PID: 188 (maxscale) Tasks: 10 (limit: 18663) Memory: 4.6M CPU: 150ms CGroup: /system.slice/maxscale.service └─188 /usr/bin/maxscale systemd[1]: Starting MariaDB MaxScale Database Proxy... maxscale[188]: Module 'galeramon' loaded from '/usr/lib/x86_64-linux-gnu/maxscale/libgaleramon.so'. maxscale[188]: Module 'schemarouter' loaded from '/usr/lib/x86_64-linux-gnu/maxscale/libschemarouter.so'. maxscale[188]: Using up to 2.3GiB of memory for query classifier cache systemd[1]: Started MariaDB MaxScale Database Proxy.

If there were errors or warnings, you can see them in the MaxScale error log:

shell> grep -v notice /var/log/maxscale/maxscale.log 2024-02-13 16:47:22 MariaDB MaxScale is shut down. ---------------------------------------------------- MariaDB MaxScale /var/log/maxscale/maxscale.log Tue Feb 13 16:47:22 2024 ---------------------------------------------------------------------------- 2024-02-27 09:52:56 warning: Discarding journal file '/var/lib/maxscale/Sharding-Monitor_journal.json'. File is for module 'mariadbmon'. Current module is 'galeramon'. 2024-02-27 09:52:56 warning: [galeramon] Invalid 'wsrep_local_index' on server 'shard1': 18446744073709551615
Application tests Simple application tests shell> mariadb --user=app --password=secret --host=10.139.158.211 --port=3306 --execute='show databases' +--------------------+ | Database | +--------------------+ | customer_0010 | | customer_0011 | | customer_0020 | | customer_0021 | | customer_0022 | | customer_0030 | | information_schema | | mysql | | performance_schema | | sys | +--------------------+
New command show shards shell> mariadb --user=app --password=secret --host=10.139.158.211 --port=3306 customer_0030 --execute='show shards' | grep customer_00.* | sort | column -t customer_0010.address shard1 customer_0010.sales shard1 customer_0010. shard1 customer_0011.address shard1 customer_0011.sales shard1 customer_0011. shard1 customer_0020.address shard2 customer_0020.sales shard2 customer_0020. shard2 customer_0021.address shard2 customer_0021.sales shard2 customer_0021. shard2 customer_0022.address shard2 customer_0022.sales shard2 customer_0022. shard2 customer_0030.address shard3 customer_0030.sales shard3 customer_0030. shard3

New databases are not displayed immediately, but only when the cached data has been updated (refresh_interval (300s / 5 min)).

See also: Custom SQL commands

More general test

As a reminder:

ShardPortCustomerState #13363customer_001<n>Running #23364customer_002<n>Running #33365customer_003<n>Running #43366customer_004<n>Running
shell> mariadb --user=app --password=secret --host=10.139.158.211 --port=3306 --execute='SELECT @@port' +--------+ | @@port | +--------+ | 3363 | +--------+ shell> mariadb --user=app --password=secret --host=10.139.158.211 --port=3306 --database=customer_0010 --execute='SELECT @@port' +--------+ | @@port | +--------+ | 3363 | +--------+ shell> mariadb --user=app --password=secret --host=10.139.158.211 --port=3306 --database=customer_0020 --execute='SELECT @@port' +--------+ | @@port | +--------+ | 3364 | +--------+ shell> mariadb --user=app --password=secret --host=10.139.158.211 --port=3306 --execute='use customer_0020; SELECT @@port' +--------+ | @@port | +--------+ | 3364 | +--------+ shell> mariadb --user=app --password=secret --host=10.139.158.211 --port=3306 customer_0010 --execute='SELECT @@port' +--------+ | @@port | +--------+ | 3363 | +--------+ shell> mariadb --user=app --password=secret --host=10.139.158.211 --port=3306 customer_0020 --execute='SELECT @@port' +--------+ | @@port | +--------+ | 3364 | +--------+ shell> mariadb --user=app --password=secret --host=10.139.158.211 --port=3306 customer_0030 --execute='SELECT @@port' +--------+ | @@port | +--------+ | 3365 | +--------+
Less simple (backup) test shell> mariadb-dump --user=app --password=secret --host=10.139.158.211 --port=3306 --single-transaction customer_0010 > /tmp/customer_0010.sql shell> echo $? 0 shell> mariadb-dump --user=app --password=secret --host=10.139.158.211 --port=3306 --single-transaction customer_0020 > /tmp/customer_0020.sql shell> echo $? 0 shell> mariadb-dump --user=app --password=secret --host=10.139.158.211 --port=3306 --single-transaction customer_0030 > /tmp/customer_0030.sql shell> echo $? 0 shell> mariadb-dump --user=app --password=secret --host=10.139.158.211 --port=3306 --single-transaction --databases customer_0011 > /tmp/customer_0011.sql shell> echo $? 0 shell> mariadb-dump --user=app --password=secret --host=10.139.158.211 --port=3306 --single-transaction --databases customer_0021 > /tmp/customer_0021.sql shell> echo $? 0 shell> mariadb-dump --user=app --password=secret --host=10.139.158.211 --port=3306 --single-transaction --databases customer_0030 > /tmp/customer_0030.sql shell> echo $? 0 shell> ll /tmp/customer_00*sql -rw-rw-r-- 1 oli oli 2738 Mar 18 12:07 /tmp/customer_0010.sql -rw-rw-r-- 1 oli oli 2904 Mar 18 12:08 /tmp/customer_0011.sql -rw-rw-r-- 1 oli oli 2712 Mar 18 12:08 /tmp/customer_0020.sql -rw-rw-r-- 1 oli oli 2906 Mar 18 12:08 /tmp/customer_0021.sql -rw-rw-r-- 1 oli oli 2964 Mar 18 12:08 /tmp/customer_0030.sql shell> tail -n 1 /tmp/customer_*.sql ==> /tmp/customer_0010.sql <== -- Dump completed on 2024-02-13 14:39:21 ==> /tmp/customer_0011.sql <== -- Dump completed on 2024-02-13 14:39:35 ==> /tmp/customer_0020.sql <== -- Dump completed on 2024-02-13 14:40:15 ==> /tmp/customer_0021.sql <== -- Dump completed on 2024-02-13 14:40:42 ==> /tmp/customer_0030.sql <== -- Dump completed on 2024-02-13 14:40:52 shell> cat /tmp/customer_00*sql | grep -A1 -i insert INSERT INTO `address` VALUES (1,'Customer 10 GmbH'); -- INSERT INTO `sales` VALUES (1,'Apples',5,1.20,6.00), -- INSERT INTO `address` VALUES (1,'Customer 11 SE'); -- INSERT INTO `sales` VALUES (1,'Oranges',2,1.70,3.40), -- INSERT INTO `address` VALUES (1,'Customer 20 AG'); -- INSERT INTO `sales` VALUES (1,'Oranges',2,1.70,3.40), -- INSERT INTO `address` VALUES (1,'Customer 21 GmbH'); -- INSERT INTO `sales` VALUES (1,'Oranges',2,1.70,3.40), -- INSERT INTO `address` VALUES (1,'Customer 30 GmbH'); -- INSERT INTO `sales` VALUES (1,'Pickles',2,2.20,4.40),

In MaxScale 23.08.4 there was a pretty bad bug: A return value of 0 but no data in the backup!!! See also the tickets: MXS-4966: mariadb-dump gets an error dumping schemas and MXS-4947: Tables in information_schema are treated as a normal tables. Symptoms of the bug look like this:

Error: Couldn't read status information for table address () Error: Couldn't read status information for table sales ()

We therefore strongly recommend upgrading to MaxScale 23.08.5!

More complex application tests

We have created a somewhat more complex test (./sharding_test.php) that processes the following queries:

SET NAMES utf8mb4 SHOW DATABASES use customer_ START TRANSACTION; SELECT MIN(id) AS first, MAX(id) AS last FROM `sales` INSERT INTO sales (id, product, sales, amount, total_amount) VALUES (%d, '%s', %f, %f, %f) INSERT INTO sales (id, product, sales, sales, amount, total_amount) VALUES (%d, '%s', %f, %f, %f) UPDATE sales SET product = 'Prepare to delete' WHERE id = %d DELETE FROM sales WHERE id = %d COMMIT

This test ran flawlessly. The corresponding control query:

SQL> SELECT * FROM customer_0021.sales WHERE id >= (SELECT MAX(id) - 10 FROM customer_0021.sales);

Various load scenarios can also be tested with db_bench or the Acronis perfkit. For more information, see here.

Cross-shard tests

In any case, you might come up with the idea of running cross-shard queries. This will NOT work, which should not really be surprising, firstly because it is not easy to implement and secondly because it is described here:

"Note: As the sharding solution in MaxScale is relatively simple, cross-database queries between two or more shards are not supported."

Source: Simple Sharding with Two Servers

and

"USE db1 is routed to the server with db1. If the database is divided to multiple servers, only one server will get the command."

Source: SchemaRouter.

Here is a test with UNION:

SQL> use customer_0030 Database changed SQL> SELECT * FROM customer_0020.sales UNION SELECT * FROM customer_0030.sales; ERROR 1146 (42S02): Table 'customer_0020.sales' doesn't exist

And here is the proof to the contrary:

SQL> use customer_0020 Database changed SQL> SELECT * FROM customer_0020.sales UNION SELECT * FROM customer_0030.sales; ERROR 1146 (42S02): Table 'customer_0030.sales' doesn't exist

And here is the test with JOIN:

SQL> use customer_0020 SQL> SELECT * FROM customer_0020.sales a JOIN customer_0030.sales b ON a.id = b.id WHERE a.sales > 1 ; ERROR 1146 (42S02): Table 'customer_0030.sales' doesn't exist SQL> use customer_0030 SQL> SELECT * FROM customer_0020.sales a JOIN customer_0030.sales b ON a.id = b.id WHERE a.sales > 1 ; ERROR 1146 (42S02): Table 'customer_0020.sales' doesn't exist
Operation of a MaxScale sharding system

In this chapter we discuss some points that can be useful for the operation of a MariaDB MaxScale sharding system.

Do-on-all-shards

Since it can always happen that O/S or database operations have to be executed on all shards, it would certainly make sense to create a script that executes the same command on all shards in turn:

shell> ./do-on-all-shards.sh --sql='SHOW DATABASES'

A script of this type should greatly reduce the error rate during operation. Operations such as the re-sharding of a tenant, as described below, are also sensibly scripted and executed centrally (MXS-5029).

Invalidating the database map cache

The invalidate command can be used to invalidate the database map cache of the MariaDB MaxScale SchemaRouter. This allows us to quickly update the cache after adding or removing tenants.

shell> maxctrl call command schemarouter invalidate Sharded-Service OK

In contrast to the invalidate command, which updates the entries after the next refresh_interval, the clear command deletes the entries and a remap is executed immediately.

If you want to invalidate the database map cache remotely with a REST API call, you can do this as follows:

shell> curl -i -X POST -u api_admin:secret http://10.139.158.211:8989/v1/maxscale/modules/schemarouter/clear?Sharded-Service HTTP/1.1 204 No Content Connection: close Date: Mon, 18 Mar 24 11:49:58 GMT X-Frame-Options: Deny X-XSS-Protection: 1 Referrer-Policy: same-origin Cache-Control: no-cache

Sources:


How to change SchemaRouter variables dynamically?

The refresh_interval specifies the lifetime of the entries in the SchemaRouter Database Map Cache. The default value is 300 s (5 min). Refresh Interval is therefore, in my opinion, an unfortunate term as it does not define the interval between two mappings but the lifetime of the cache entries (livetime?, timeout?). As soon as the entry has been deleted, a new refresh of the "database map" is triggered on each shard. The command currently looks like this:

SELECT LOWER(t.table_schema), LOWER(t.table_name) FROM information_schema.tables t UNION ALL SELECT LOWER(s.schema_name), '' FROM information_schema.schemata s

It looks like a simple connect is enough to trigger the refresh of the database map.

The current value for refresh_interval can be queried as follows:

shell> maxctrl show service Sharded-Service | grep refresh_interval | awk -F'│' '{ print $3 }' "refresh_interval": "300000ms",

The following command helps to change the value dynamically:

shell> MAXCTRL_WARNINGS=0 maxctrl alter service Sharded-Service refresh_interval=10s OK

The value should not be set too small, as all other connections are stopped during the mapping process.

Sources:


Adding and removing a tenant

Adding a new tenant to a shard is not a major problem:

SQL> CREATE DATABASE customer_0029; SQL> use customer_0029 SQL> CREATE TABLE address LIKE customer_template.address; SQL> CREATE TABLE sales LIKE customer_template.sales; shell> maxctrl call command schemarouter invalidate Sharded-Service OK

Removing a tenant from a shard, on the other hand, is somewhat more complicated and must be done in consultation with the application:

SQL> DROP DATABASE customer_0011; shell> ./sharding_test.php .....ERROR: Table 'customer_0011.sales' doesn't exist...ERROR: Unknown database 'customer_0011'.ERROR: Unknown database 'customer_0011'......ERROR: Unknown database 'customer_0011'... shell> maxctrl call command schemarouter clear Sharded-Service OK

At least I have not come up with a cleverer variant yet. See also Moving a tenant below.

Moving a tenant

The combination of adding and removing would then be moving a tenant from one shard to another shard, also known as re-sharding. This also requires a concerted action to be planned together with the application.

If this is not possible, at least the time that the application receives errors can be reduced... The following procedure can be used to move a tenant from shard 2 to shard 3:

SQL> use customer_0020; LOCK TABLES address READ, sales READ; -- On Shard 2, application will be blocked at best! shell> mariadb-dump --user=app --password=secret --host=10.139.158.1 --port=3364 --single-transaction --skip-add-locks --databases customer_0020 | mariadb --user=app --password=secret --host=10.139.158.1 --port=3365 # Copy tenant 20 from shard 2 to shard 3 SQL> DROP DATABASE customer_0020; -- Deleting tenant 20 does not work! ERROR 1192 (HY000): Can't execute the given command because you have active locked tables or an active transaction SQL> UNLOCK TABLES; DROP DATABASE customer_0020; # How to delete tenant 20. shell> maxctrl call command schemarouter clear Sharded-Service # Update MaxScale Database Map. Do it quickly!!!

Until the database map is refreshed, the following errors may occur:

error : (47621) [schemarouter] (Sharded-Service); 'customer_0020.' found on servers 'shard2','shard3' for user 'app'@'10.139.158.1'. error : (47621) [schemarouter] (Sharded-Service); 'customer_0020.address' found on servers 'shard2','shard3' for user 'app'@'10.139.158.1'. error : (47621) [schemarouter] (Sharded-Service); 'customer_0020.sales' found on servers 'shard2','shard3' for user 'app'@'10.139.158.1'. error : (47621) [schemarouter] (Sharded-Service); Duplicate tables found, closing session.

And on the application side too:

ERROR: Error: duplicate tables found on two different shards
Adding or removing a shard

Moving a tenant from one shard to another shard is a small re-sharding operation. It becomes somewhat more complex if you want to add new shards or remove old shards. Subsequently (after the addition or before the removal), a large re-sharding would then take place. The first step is to add a shard to the cluster:

shell> maxctrl list servers ┌────────┬──────────────┬──────┬─────────────┬─────────┬───────────────┬──────────────────┐ │ Server │ Address │ Port │ Connections │ State │ GTID │ Monitor │ ├────────┼──────────────┼──────┼─────────────┼─────────┼───────────────┼──────────────────┤ │ shard1 │ 10.139.158.1 │ 3363 │ 0 │ Running │ 0-3363-26014 │ Sharding-Monitor │ ├────────┼──────────────┼──────┼─────────────┼─────────┼───────────────┼──────────────────┤ │ shard2 │ 10.139.158.1 │ 3364 │ 0 │ Running │ 0-3364-240612 │ Sharding-Monitor │ ├────────┼──────────────┼──────┼─────────────┼─────────┼───────────────┼──────────────────┤ │ shard3 │ 10.139.158.1 │ 3365 │ 0 │ Running │ 0-3365-289873 │ Sharding-Monitor │ └────────┴──────────────┴──────┴─────────────┴─────────┴───────────────┴──────────────────┘

The prepared shard is made known to MaxScale:

shell> maxctrl create server shard4 10.139.158.1 3366 OK shell> maxctrl list servers ┌────────┬──────────────┬──────┬─────────────┬─────────┬──────────────┬──────────────────┐ │ Server │ Address │ Port │ Connections │ State │ GTID │ Monitor │ ├────────┼──────────────┼──────┼─────────────┼─────────┼──────────────┼──────────────────┤ │ shard1 │ 10.139.158.1 │ 3363 │ 1 │ Running │ 0-3363-23676 │ Sharding-Monitor │ ├────────┼──────────────┼──────┼─────────────┼─────────┼──────────────┼──────────────────┤ │ shard2 │ 10.139.158.1 │ 3364 │ 1 │ Running │ 0-3364-52321 │ Sharding-Monitor │ ├────────┼──────────────┼──────┼─────────────┼─────────┼──────────────┼──────────────────┤ │ shard3 │ 10.139.158.1 │ 3365 │ 1 │ Running │ 0-3365-39751 │ Sharding-Monitor │ ├────────┼──────────────┼──────┼─────────────┼─────────┼──────────────┼──────────────────┤ │ shard4 │ 10.139.158.1 │ 3366 │ 0 │ Down │ │ │ └────────┴──────────────┴──────┴─────────────┴─────────┴──────────────┴──────────────────┘

The new shard is then linked to the MaxScale Monitor and the service:

shell> MAXCTRL_WARNINGS=0 maxctrl link monitor Sharding monitor shard4 OK shell> MAXCTRL_WARNINGS=0 maxctrl link service Sharded service shard4 OK shell> maxctrl list servers ┌────────┬──────────────┬──────┬─────────────┬─────────┬──────────────┬──────────────────┐ │ Server │ Address │ Port │ Connections │ State │ GTID │ Monitor │ ├────────┼──────────────┼──────┼─────────────┼─────────┼──────────────┼──────────────────┤ │ shard1 │ 10.139.158.1 │ 3363 │ 1 │ Running │ 0-3363-24961 │ Sharding-Monitor │ ├────────┼──────────────┼──────┼─────────────┼─────────┼──────────────┼──────────────────┤ │ shard2 │ 10.139.158.1 │ 3364 │ 1 │ Running │ 0-3364-56215 │ Sharding-Monitor │ ├────────┼──────────────┼──────┼─────────────┼─────────┼──────────────┼──────────────────┤ │ shard3 │ 10.139.158.1 │ 3365 │ 1 │ Running │ 0-3365-45177 │ Sharding-Monitor │ ├────────┼──────────────┼──────┼─────────────┼─────────┼──────────────┼──────────────────┤ │ shard4 │ 10.139.158.1 │ 3366 │ 1 │ Running │ 0-3366-32 │ Sharding-Monitor │ └────────┴──────────────┴──────┴─────────────┴─────────┴──────────────┴──────────────────┘

Whether this second step is also absolutely necessary was not investigated.

You can follow the entire process in the MariaDB MaxScale error log:

warning: Discarding journal file '/var/lib/maxscale/Sharding-Monitor_journal.json'. Servers described in the journal are different from the ones configured on the current monitor. warning: Saving runtime modifications to 'Sharding-Monitor' in '/var/lib/maxscale/maxscale.cnf.d/Sharding-Monitor.cnf'. The modified values will override the values found in the static configuration files. notice : shard4 sent version string '10.11.7-MariaDB-log'. Detected type: MariaDB, version: 10.11.7. notice : Server 'shard4' charset: latin1_swedish_ci notice : Server changed state: shard4[10.139.158.1:3366]: server_up. [Down] -> [Running] warning: Saving runtime modifications to 'Sharded-Service' in '/var/lib/maxscale/maxscale.cnf.d/Sharded-Service.cnf'. The modified values will override the values found in the static configuration files. notice : Added 'shard4' to 'Sharded-Service'

What we must not forget here is to also equip the new shard with the proxy protocol:

shell> maxctrl show server shard4 | grep proxy │ │ "proxy_protocol": false, │ MAXCTRL_WARNINGS=0 maxctrl alter server shard4 proxy_protocol=true OK

And now new tenants can be added to the new shard or old tenants can be moved to the new shard... In our setup, we want to move all tenants from shard 1 to shard 4 and also create a new tenant customer_0040 on shard 4. The individual steps required for this are listed above.

Once shard 1 has been emptied, it can be dismantled:

shell> maxctrl list servers ┌────────┬──────────────┬──────┬─────────────┬─────────┬──────────────┬──────────────────┐ │ Server │ Address │ Port │ Connections │ State │ GTID │ Monitor │ ├────────┼──────────────┼──────┼─────────────┼─────────┼──────────────┼──────────────────┤ │ shard1 │ 10.139.158.1 │ 3363 │ 1 │ Running │ 0-3363-25916 │ Sharding-Monitor │ ├────────┼──────────────┼──────┼─────────────┼─────────┼──────────────┼──────────────────┤ │ shard2 │ 10.139.158.1 │ 3364 │ 1 │ Running │ 0-3364-62887 │ Sharding-Monitor │ ├────────┼──────────────┼──────┼─────────────┼─────────┼──────────────┼──────────────────┤ │ shard3 │ 10.139.158.1 │ 3365 │ 1 │ Running │ 0-3365-54035 │ Sharding-Monitor │ ├────────┼──────────────┼──────┼─────────────┼─────────┼──────────────┼──────────────────┤ │ shard4 │ 10.139.158.1 │ 3366 │ 1 │ Running │ 0-3366-2247 │ Sharding-Monitor │ └────────┴──────────────┴──────┴─────────────┴─────────┴──────────────┴──────────────────┘

A shard is deleted with the destroy server command. Before this works, however, a shard must be removed from the monitor and the service:

shell> MAXCTRL_WARNINGS=0 maxctrl unlink service Sharded service shard1 OK shell> MAXCTRL_WARNINGS=0 maxctrl unlink monitor Sharding monitor shard1 OK shell> maxctrl list servers ┌────────┬──────────────┬──────┬─────────────┬─────────┬──────────────┬──────────────────┐ │ Server │ Address │ Port │ Connections │ State │ GTID │ Monitor │ ├────────┼──────────────┼──────┼─────────────┼─────────┼──────────────┼──────────────────┤ │ shard1 │ 10.139.158.1 │ 3363 │ 0 │ Running │ │ │ ├────────┼──────────────┼──────┼─────────────┼─────────┼──────────────┼──────────────────┤ │ shard2 │ 10.139.158.1 │ 3364 │ 1 │ Running │ 0-3364-64394 │ Sharding-Monitor │ ├────────┼──────────────┼──────┼─────────────┼─────────┼──────────────┼──────────────────┤ │ shard3 │ 10.139.158.1 │ 3365 │ 1 │ Running │ 0-3365-56072 │ Sharding-Monitor │ ├────────┼──────────────┼──────┼─────────────┼─────────┼──────────────┼──────────────────┤ │ shard4 │ 10.139.158.1 │ 3366 │ 1 │ Running │ 0-3366-3267 │ Sharding-Monitor │ └────────┴──────────────┴──────┴─────────────┴─────────┴──────────────┴──────────────────┘

Once the shard has been removed from the monitor and the service, it can then be deleted:

shell> maxctrl destroy server shard1 Warning: Object 'shard1' is defined in a static configuration file and cannot be permanently deleted. If MaxScale is restarted, the object will appear again. To hide these warnings, run: export MAXCTRL_WARNINGS=0 OK shell> maxctrl list servers ┌────────┬──────────────┬──────┬─────────────┬─────────┬──────────────┬──────────────────┐ │ Server │ Address │ Port │ Connections │ State │ GTID │ Monitor │ ├────────┼──────────────┼──────┼─────────────┼─────────┼──────────────┼──────────────────┤ │ shard2 │ 10.139.158.1 │ 3364 │ 1 │ Running │ 0-3364-65018 │ Sharding-Monitor │ ├────────┼──────────────┼──────┼─────────────┼─────────┼──────────────┼──────────────────┤ │ shard3 │ 10.139.158.1 │ 3365 │ 1 │ Running │ 0-3365-56886 │ Sharding-Monitor │ ├────────┼──────────────┼──────┼─────────────┼─────────┼──────────────┼──────────────────┤ │ shard4 │ 10.139.158.1 │ 3366 │ 1 │ Running │ 0-3366-3648 │ Sharding-Monitor │ └────────┴──────────────┴──────┴─────────────┴─────────┴──────────────┴──────────────────┘

And you can follow the changes in the MaxScale Error Log:

notice : Removed 'shard1' from 'Sharded-Service' warning: Discarding journal file '/var/lib/maxscale/Sharding-Monitor_journal.json'. Servers described in the journal are different from the ones configured on the current monitor. notice : Destroyed server 'shard1' at 10.139.158.1:3363

Important: I was informed that with destroy server --force the unlink service and unlink monitor commands are automatically executed by MaxScale.

Source:


Customising the configuration files

During the shard operations described above we received some warnings:

Warning: Object 'shard1' is defined in a static configuration file and cannot be permanently deleted. If MaxScale is restarted, the object will appear again.

and

Warning: Saving runtime modifications to 'Sharding-Monitor' in '/var/lib/maxscale/maxscale.cnf.d/Sharding-Monitor.cnf'. The modified values will override the values found in the static configuration files.

The corresponding configuration files are automatically created by MaxScale when dynamic system changes are made:

shell> ll /var/lib/maxscale/maxscale.cnf.d/ /etc/maxscale.cnf -rw-r--r-- 1 root root 612 Feb 13 14:23 /etc/maxscale.cnf /var/lib/maxscale/maxscale.cnf.d/: total 12 -rw------- 1 maxscale maxscale 187 Feb 13 16:08 Sharding-Monitor.cnf -rw------- 1 maxscale maxscale 150 Feb 13 16:07 Sharded-Service.cnf -rw------- 1 maxscale maxscale 52 Feb 13 15:46 shard4.cnf cat /var/lib/maxscale/maxscale.cnf.d/* [Sharded-Service] debug=true refresh_interval=10000ms auth_all_servers=true log_debug=true password=secret router=schemarouter type=service user=maxscale_admin targets=shard2,shard3,shard4 [sharding monitor] module=galeramon monitor_interval=1000ms password=secret servers=shard2,shard3,shard4 type=monitor user=maxscale_monitor [shard4] address=10.139.158.1 port=3366 type=server

The configuration files still need to be improved accordingly. You should generally consider whether you should not configure everything dynamically via commands in a highly dynamic system...

Maintenance work on the shard

If a shard is to be taken offline for maintenance work, here in the example shard2, this can be done as follows:

shell> maxctrl list servers ┌────────┬──────────────┬──────┬─────────────┬─────────┬──────────────┬──────────────────┐ │ Server │ Address │ Port │ Connections │ State │ GTID │ Monitor │ ├────────┼──────────────┼──────┼─────────────┼─────────┼──────────────┼──────────────────┤ │ shard2 │ 10.139.158.1 │ 3364 │ 1 │ Running │ 0-3364-69817 │ Sharding-Monitor │ ├────────┼──────────────┼──────┼─────────────┼─────────┼──────────────┼──────────────────┤ │ shard3 │ 10.139.158.1 │ 3365 │ 1 │ Running │ 0-3365-63166 │ Sharding-Monitor │ ├────────┼──────────────┼──────┼─────────────┼─────────┼──────────────┼──────────────────┤ │ shard4 │ 10.139.158.1 │ 3366 │ 1 │ Running │ 0-3366-6902 │ Sharding-Monitor │ └────────┴──────────────┴──────┴─────────────┴─────────┴──────────────┴──────────────────┘ shell> maxctrl set server shard2 drain OK shell> maxctrl set server shard2 maintenance OK shell> maxctrl list servers ┌────────┬──────────────┬──────┬─────────────┬──────────────────────┬───────────────┬──────────────────┐ │ Server │ Address │ Port │ Connections │ State │ GTID │ Monitor │ ├────────┼──────────────┼──────┼─────────────┼──────────────────────┼───────────────┼──────────────────┤ │ shard2 │ 10.139.158.1 │ 3364 │ 0 │ Maintenance, Running │ 0-3364-240612 │ Sharding-Monitor │ ├────────┼──────────────┼──────┼─────────────┼──────────────────────┼───────────────┼──────────────────┤ │ shard3 │ 10.139.158.1 │ 3365 │ 0 │ Running │ 0-3365-289873 │ Sharding-Monitor │ ├────────┼──────────────┼──────┼─────────────┼──────────────────────┼───────────────┼──────────────────┤ │ shard4 │ 10.139.158.1 │ 3366 │ 0 │ Running │ 0-3366-119848 │ Sharding-Monitor │ └────────┴──────────────┴──────┴─────────────┴──────────────────────┴───────────────┴──────────────────┘

At this point, maintenance work can be carried out on the machine or the database...

Afterwards, BOTH statuses must be cleared again if both have been set (MXS-5028):

shell> maxctrl clear server shard2 maintenance OK shell> maxctrl clear server shard2 drain OK shell> maxctrl list servers ┌────────┬──────────────┬──────┬─────────────┬─────────┬───────────────┬──────────────────┐ │ Server │ Address │ Port │ Connections │ State │ GTID │ Monitor │ ├────────┼──────────────┼──────┼─────────────┼─────────┼───────────────┼──────────────────┤ │ shard2 │ 10.139.158.1 │ 3364 │ 0 │ Running │ 0-3364-240612 │ Sharding-Monitor │ ├────────┼──────────────┼──────┼─────────────┼─────────┼───────────────┼──────────────────┤ │ shard3 │ 10.139.158.1 │ 3365 │ 0 │ Running │ 0-3365-289873 │ Sharding-Monitor │ ├────────┼──────────────┼──────┼─────────────┼─────────┼───────────────┼──────────────────┤ │ shard4 │ 10.139.158.1 │ 3366 │ 0 │ Running │ 0-3366-119848 │ Sharding-Monitor │ └────────┴──────────────┴──────┴─────────────┴─────────┴───────────────┴──────────────────┘

The difference between drain and maintenance is that with drain, no new connections are allowed to the shard, but existing connections wait until they are closed. With maintenance, the connections are terminated immediately by force.

Observation of a MariaDB MaxScale sharding system

The MaxScale CLI client maxtrl can be used to query the status of the MariaDB MaxScale load balancer. There are numerous commands for this, mainly list and show:

shell> maxctrl show module schemarouter | head -n 12 ┌─────────────┬────────────────────────────────────────────────┐ │ Module │ schemarouter │ ├─────────────┼────────────────────────────────────────────────┤ │ Type │ Router │ ├─────────────┼────────────────────────────────────────────────┤ │ Version │ V1.0.0 │ ├─────────────┼────────────────────────────────────────────────┤ │ Maturity │ Beta │ ├─────────────┼────────────────────────────────────────────────┤ │ Description │ A database sharding router for simple sharding │ ├─────────────┼────────────────────────────────────────────────┤ │ Parameters │ ... │ shell> maxctrl list servers ┌────────┬──────────────┬──────┬─────────────┬─────────┬───────────────┬──────────────────┐ │ Server │ Address │ Port │ Connections │ State │ GTID │ Monitor │ ├────────┼──────────────┼──────┼─────────────┼─────────┼───────────────┼──────────────────┤ │ shard2 │ 10.139.158.1 │ 3364 │ 4 │ Running │ 0-3364-290859 │ Sharding-Monitor │ ├────────┼──────────────┼──────┼─────────────┼─────────┼───────────────┼──────────────────┤ │ shard3 │ 10.139.158.1 │ 3365 │ 4 │ Running │ 0-3365-322671 │ Sharding-Monitor │ ├────────┼──────────────┼──────┼─────────────┼─────────┼───────────────┼──────────────────┤ │ shard4 │ 10.139.158.1 │ 3366 │ 4 │ Running │ 0-3366-140018 │ Sharding-Monitor │ └────────┴──────────────┴──────┴─────────────┴─────────┴───────────────┴──────────────────┘

The information for the Connections column is confusing because in this case we only have 1, 1 and 2 connections open on each shard in this sharding system.

However, if you look at the situation on the respective shard with SHOW PROCESSLIST, you can see that MaxScale also establishes a connection on EACH shard for each incoming connection. So the display above is actually technically correct, just not what you would expect:

SQL> SHOW PROCESSLIST; +--------+------------------+----------------------+---------------+---------+------+----------+-----------------------------------------------------------------+----------+ | Id | User | Host | db | Command | Time | State | Info | Progress | +--------+------------------+----------------------+---------------+---------+------+----------+-----------------------------------------------------------------+----------+ | 123 | root | localhost | customer_0021 | Query | 0 | starting | show processlist | 0.000 | | 68107 | maxscale_monitor | 10.139.158.211:35418 | NULL | Sleep | 0 | | NULL | 0.000 | | 113372 | app | 10.139.158.1:47548 | NULL | Sleep | 47 | | NULL | 0.000 | | 113538 | app | 10.139.158.1:49058 | NULL | Sleep | 41 | | NULL | 0.000 | | 113662 | app | 10.139.158.1:47072 | NULL | Sleep | 37 | | NULL | 0.000 | | 114789 | app | 10.139.158.1:39574 | customer_0022 | Query | 0 | Updating | UPDATE sales SET product = 'Prepare to delete' WHERE id = 15622 | 0.000 | +--------+------------------+----------------------+---------------+---------+------+----------+-----------------------------------------------------------------+----------+

This does not scale with large systems with hundreds or thousands of clients! Maybe the MariaDB thread pool feature is used in this case.

According to the MaxScale developer, this is expected behaviour... (MXS-4977)

shell> maxctrl list services ┌─────────────────┬──────────────┬─────────────┬───────────────────┬────────────────────────┐ │ Service │ Router │ Connections │ Total Connections │ Targets │ ├─────────────────┼──────────────┼─────────────┼───────────────────┼────────────────────────┤ │ Sharded-Service │ schemarouter │ 4 │ 82776 │ shard2, shard3, shard4 │ └─────────────────┴──────────────┴─────────────┴───────────────────┴────────────────────────┘ shell> maxctrl list listeners ┌──────────────────────────┬──────┬──────┬─────────┬─────────────────┐ │ Name │ Port │ Host │ State │ Service │ ├──────────────────────────┼──────┼──────┼─────────┼─────────────────┤ │ Sharded-Service-Listener │ 3306 │ :: │ Running │ Sharded-Service │ └──────────────────────────┴──────┴──────┴─────────┴─────────────────┘ shell> maxctrl list monitors ┌──────────────────┬─────────┬────────────────────────┐ │ Monitor │ State │ Servers │ ├──────────────────┼─────────┼────────────────────────┤ │ Sharding-Monitor │ Running │ shard2, shard3, shard4 │ └──────────────────┴─────────┴────────────────────────┘ shell> maxctrl show server shard2 | head -n 20 ┌─────────────────────┬──────────────────────────────────────────────┐ │ Server │ shard2 │ ├─────────────────────┼──────────────────────────────────────────────┤ │ Source │ /etc/maxscale.cnf │ ├─────────────────────┼──────────────────────────────────────────────┤ │ Address │ 10.139.158.1 │ ├─────────────────────┼──────────────────────────────────────────────┤ │ Port │ 3364 │ ├─────────────────────┼──────────────────────────────────────────────┤ │ State │ Running │ ├─────────────────────┼──────────────────────────────────────────────┤ │ Version │ 10.11.7-MariaDB-log │ ├─────────────────────┼──────────────────────────────────────────────┤ │ Uptime │ 178960 │ ├─────────────────────┼──────────────────────────────────────────────┤ │ Last Event │ server_down │ ├─────────────────────┼──────────────────────────────────────────────┤ │ Triggered At │ Sun, 04 Feb 2024 07:37:17 GMT │ ├─────────────────────┼──────────────────────────────────────────────┤ │ Services │ Sharded-Service │ ├─────────────────────┼──────────────────────────────────────────────┤ │ Monitors │ Sharding-Monitor │ ├─────────────────────┼──────────────────────────────────────────────┤ ... ├─────────────────────┼──────────────────────────────────────────────┤ │ Current Connections │ 5 │ ├─────────────────────┼──────────────────────────────────────────────┤ │ Total Connections │ 27 │ ├─────────────────────┼──────────────────────────────────────────────┤ │ Max Connections │ 5 │ shell> maxctrl show service Sharded-Service ┌─────────────────────┬──────────────────────────────────────────────────────┐ │ Service │ Sharded-Service │ ├─────────────────────┼──────────────────────────────────────────────────────┤ │ Source │ /var/lib/maxscale/maxscale.cnf.d/Sharded-Service.cnf │ ├─────────────────────┼──────────────────────────────────────────────────────┤ │ Router │ schemarouter │ ├─────────────────────┼──────────────────────────────────────────────────────┤ │ State │ Started │ ├─────────────────────┼──────────────────────────────────────────────────────┤ │ Started At │ 3/18/2024, 1:52:30 PM │ ├─────────────────────┼──────────────────────────────────────────────────────┤ │ Users Loaded At │ 3/18/2024, 1:52:30 PM │ ├─────────────────────┼──────────────────────────────────────────────────────┤ │ Current Connections │ 4 │ ├─────────────────────┼──────────────────────────────────────────────────────┤ │ Total Connections │ 84590 │ ├─────────────────────┼──────────────────────────────────────────────────────┤ │ Max Connections │ 5 │ ├─────────────────────┼──────────────────────────────────────────────────────┤ │ Cluster │ │ ├─────────────────────┼──────────────────────────────────────────────────────┤ │ Servers │ shard2 │ │ │ shard3 │ │ │ shard4 │ ├─────────────────────┼──────────────────────────────────────────────────────┤ │ Services │ │ ├─────────────────────┼──────────────────────────────────────────────────────┤ │ Filters │ │ ├─────────────────────┼──────────────────────────────────────────────────────┤ │ Parameters │ { │ │ │ "auth_all_servers": true, │ │ │ "connection_keepalive": "300000ms", │ │ │ "debug": true, │ │ │ "disable_sescmd_history": false, │ │ │ "enable_root_user": false, │ │ │ "force_connection_keepalive": false, │ │ │ "idle_session_pool_time": "-1ms", │ │ │ "ignore_tables": [], │ │ │ "ignore_tables_regex": null, │ │ │ "localhost_match_wildcard_host": true, │ │ │ "log_auth_warnings": true, │ │ │ "log_debug": true, │ │ │ "log_info": false, │ │ │ "log_notice": false, │ │ │ "log_warning": false, │ │ │ "max_connections": 0, │ │ │ "max_sescmd_history": 50, │ │ │ "max_staleness": "150000ms", │ │ │ "multiplex_timeout": "60000ms", │ │ │ "net_write_timeout": "0ms", │ │ │ "password": "*****", │ │ │ "prune_sescmd_history": true, │ │ │ "rank": "primary", │ │ │ "refresh_databases": false, │ │ │ "refresh_interval": "10000ms", │ │ │ "retain_last_statements": -1, │ │ │ "router": "schemarouter", │ │ │ "session_trace": false, │ │ │ "strip_db_esc": true, │ │ │ "type": "service", │ │ │ "user": "maxscale_admin", │ │ │ "user_accounts_file": null, │ │ │ "user_accounts_file_usage": "add_when_load_ok", │ │ │ "version_string": null, │ │ │ "wait_timeout": "0ms" │ │ │ } │ ├─────────────────────┼──────────────────────────────────────────────────────┤ │ Router Diagnostics │ { │ │ │ "average_session": 0.028822357131634554, │ │ │ "longest_sescmd_chain": 4, │ │ │ "longest_session": 50, │ │ │ "queries": 761134, │ │ │ "sescmd_percentage": 44.44342257736483, │ │ │ "shard_map_hits": 84356, │ │ │ "shard_map_misses": 5, │ │ │ "shard_map_stale": 229, │ │ │ "shard_map_updates": 216, │ │ │ "shortest_session": 0, │ │ │ "times_sescmd_limit_exceeded": 0 │ │ │ } │ └─────────────────────┴──────────────────────────────────────────────────────┘

See also MaxScale SchemaRouter Router diagnostics.

shell> maxctrl show monitor Sharding-Monitor ┌─────────────────────┬──────────────────────────────────────────────────────────┐ │ Monitor │ Sharding-Monitor │ ├─────────────────────┼──────────────────────────────────────────────────────────┤ │ Source │ /etc/maxscale.cnf │ ├─────────────────────┼──────────────────────────────────────────────────────────┤ │ Module │ galeramon │ ├─────────────────────┼──────────────────────────────────────────────────────────┤ │ State │ Running │ ├─────────────────────┼──────────────────────────────────────────────────────────┤ │ Servers │ shard1 │ │ │ shard2 │ │ │ shard3 │ ├─────────────────────┼──────────────────────────────────────────────────────────┤ │ Parameters │ { │ │ │ "available_when_donor": false, │ │ │ "backend_connect_attempts": 1, │ │ │ "backend_connect_timeout": "3000ms", │ │ │ "backend_read_timeout": "3000ms", │ │ │ "backend_write_timeout": "3000ms", │ │ │ "disable_master_failback": false, │ │ │ "disable_master_role_setting": false, │ │ │ "disk_space_check_interval": "0ms", │ │ │ "disk_space_threshold": null, │ │ │ "events": "all,master_down,master_up,...,new_donor", │ │ │ "journal_max_age": "28800000ms", │ │ │ "module": "galeramon", │ │ │ "monitor_interval": "1000ms", │ │ │ "password": "*****", │ │ │ "root_node_as_master": false, │ │ │ "script": null, │ │ │ "script_timeout": "90000ms", │ │ │ "set_donor_nodes": false, │ │ │ "type": "monitor", │ │ │ "use_priority": false, │ │ │ "user": "maxscale_monitor" │ │ │ } │ ├─────────────────────┼──────────────────────────────────────────────────────────┤ │ Monitor Diagnostics │ { │ │ │ "disable_master_failback": false, │ │ │ "disable_master_role_setting": false, │ │ │ "root_node_as_master": false, │ │ │ "server_info": [ │ │ │ { │ │ │ "gtid_binlog_pos": "0-3363-26014", │ │ │ "gtid_current_pos": "0-3363-26014", │ │ │ "master_id": 0, │ │ │ "name": "shard1", │ │ │ "read_only": false, │ │ │ "server_id": 3363 │ │ │ }, │ │ │ { │ │ │ "gtid_binlog_pos": "0-3364-240612", │ │ │ "gtid_current_pos": "0-3364-240612", │ │ │ "master_id": 0, │ │ │ "name": "shard2", │ │ │ "read_only": false, │ │ │ "server_id": 3364 │ │ │ }, │ │ │ { │ │ │ "gtid_binlog_pos": "0-3365-289873", │ │ │ "gtid_current_pos": "0-3365-289873", │ │ │ "master_id": 0, │ │ │ "name": "shard3", │ │ │ "read_only": false, │ │ │ "server_id": 3365 │ │ │ } │ │ │ ], │ │ │ "set_donor_nodes": false, │ │ │ "use_priority": false │ │ │ } │ └─────────────────────┴──────────────────────────────────────────────────────────┘ shell> maxctrl list sessions; ┌───────┬──────┬──────────────┬───────────────────────┬───────┬─────────────────┬────────┬──────────────┐ │ Id │ User │ Host │ Connected │ Idle │ Service │ Memory │ I/O-Activity │ ├───────┼──────┼──────────────┼───────────────────────┼───────┼─────────────────┼────────┼──────────────┤ │ 87240 │ app │ 10.139.158.1 │ 3/18/2024, 2:33:54 PM │ 0 │ Sharded-Service │ 68644 │ 33 │ ├───────┼──────┼──────────────┼───────────────────────┼───────┼─────────────────┼────────┼──────────────┤ │ 72654 │ app │ 10.139.158.1 │ 3/18/2024, 2:25:27 PM │ 506.3 │ Sharded-Service │ 199328 │ 0 │ ├───────┼──────┼──────────────┼───────────────────────┼───────┼─────────────────┼────────┼──────────────┤ │ 72364 │ app │ 10.139.158.1 │ 3/18/2024, 2:25:18 PM │ 516 │ Sharded-Service │ 199328 │ 0 │ ├───────┼──────┼──────────────┼───────────────────────┼───────┼─────────────────┼────────┼──────────────┤ │ 72530 │ app │ 10.139.158.1 │ 3/18/2024, 2:25:23 PM │ 510.5 │ Sharded-Service │ 199328 │ 0 │ └───────┴──────┴──────────────┴───────────────────────┴───────┴─────────────────┴────────┴──────────────┘ shell> maxctrl show session 26 ┌───────────────────────┬───────────────────────────────────────┐ │ Id │ 26 │ ├───────────────────────┼───────────────────────────────────────┤ │ Service │ Sharded-Service │ ├───────────────────────┼───────────────────────────────────────┤ │ State │ Session started │ ├───────────────────────┼───────────────────────────────────────┤ │ User │ app │ ├───────────────────────┼───────────────────────────────────────┤ │ Host │ 10.139.158.1 │ ├───────────────────────┼───────────────────────────────────────┤ │ Port │ 42854 │ ├───────────────────────┼───────────────────────────────────────┤ │ Database │ │ ├───────────────────────┼───────────────────────────────────────┤ │ Connected │ 2/4/2024, 9:31:12 AM │ ├───────────────────────┼───────────────────────────────────────┤ │ Idle │ 610.4 │ ├───────────────────────┼───────────────────────────────────────┤ │ Parameters │ { │ │ │ "log_error": false, │ │ │ "log_info": false, │ │ │ "log_notice": false, │ │ │ "log_warning": false │ │ │ } │ ├───────────────────────┼───────────────────────────────────────┤ │ Client TLS Cipher │ │ ├───────────────────────┼───────────────────────────────────────┤ │ Connection attributes │ { │ │ │ "_client_name": "libmariadb", │ │ │ "_client_version": "3.3.8", │ │ │ "_os": "Linux", │ │ │ "_pid": "251037", │ │ │ "_platform": "x86_64", │ │ │ "_server_host": "10.139.158.211", │ │ │ "program_name": "mysql" │ │ │ } │ ├───────────────────────┼───────────────────────────────────────┤ │ Connections │ shard1 │ │ │ shard2 │ │ │ shard3 │ ├───────────────────────┼───────────────────────────────────────┤ │ Connection IDs │ 666 │ │ │ 139 │ │ │ 138 │ ├───────────────────────┼───────────────────────────────────────┤ │ Queries │ │ ├───────────────────────┼───────────────────────────────────────┤ │ Log │ │ ├───────────────────────┼───────────────────────────────────────┤ │ Memory │ { │ │ │ "connection_buffers": { │ │ │ "backends": { │ │ │ "shard1": { │ │ │ "misc": 678, │ │ │ "readq": 65536, │ │ │ "total": 66214, │ │ │ "writeq": 0 │ │ │ }, │ │ │ "shard2": { │ │ │ "misc": 662, │ │ │ "readq": 0, │ │ │ "total": 662, │ │ │ "writeq": 0 │ │ │ }, │ │ │ "shard3": { │ │ │ "misc": 678, │ │ │ "readq": 65536, │ │ │ "total": 66214, │ │ │ "writeq": 0 │ │ │ } │ │ │ }, │ │ │ "client": { │ │ │ "misc": 654, │ │ │ "readq": 65536, │ │ │ "total": 66190, │ │ │ "writeq": 0 │ │ │ }, │ │ │ "total": 199280 │ │ │ }, │ │ │ "exec_metadata": 0, │ │ │ "last_queries": 0, │ │ │ "sescmd_history": 48, │ │ │ "total": 199328, │ │ │ "variables": 0 │ │ │ } │ ├───────────────────────┼───────────────────────────────────────┤ │ I/O Activity │ 0 │ └───────────────────────┴───────────────────────────────────────┘ shell> maxctrl show listener Sharded-Service-Listener ┌────────────┬───────────────────────────────────────────┐ │ Name │ Sharded-Service-Listener │ ├────────────┼───────────────────────────────────────────┤ │ Source │ /etc/maxscale.cnf │ ├────────────┼───────────────────────────────────────────┤ │ Service │ Sharded-Service │ ├────────────┼───────────────────────────────────────────┤ │ Parameters │ { │ │ │ "MariaDBProtocol": { │ │ │ "allow_replication": true │ │ │ }, │ │ │ "address": "::", │ │ │ "authenticator": null, │ │ │ "authenticator_options": null, │ │ │ "connection_init_sql_file": null, │ │ │ "connection_metadata": [ │ │ │ "character_set_client=auto", │ │ │ "character_set_connection=auto", │ │ │ "character_set_results=auto", │ │ │ "max_allowed_packet=auto", │ │ │ "system_time_zone=auto", │ │ │ "time_zone=auto", │ │ │ "tx_isolation=auto" │ │ │ ], │ │ │ "port": 3306, │ │ │ "protocol": "MariaDBProtocol", │ │ │ "proxy_protocol_networks": null, │ │ │ "service": "Sharded-Service", │ │ │ "socket": null, │ │ │ "sql_mode": "default", │ │ │ "ssl": false, │ │ │ "ssl_ca": null, │ │ │ "ssl_cert": null, │ │ │ "ssl_cert_verify_depth": 9, │ │ │ "ssl_cipher": null, │ │ │ "ssl_crl": null, │ │ │ "ssl_key": null, │ │ │ "ssl_verify_peer_certificate": false, │ │ │ "ssl_verify_peer_host": false, │ │ │ "ssl_version": "MAX", │ │ │ "type": "listener", │ │ │ "user_mapping_file": null │ │ │ } │ └────────────┴───────────────────────────────────────────┘ shell> maxctrl show module schemarouter ┌─────────────┬─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┐ │ Module │ schemarouter │ ├─────────────┼─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┤ │ Type │ Router │ ├─────────────┼─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┤ │ Version │ V1.0.0 │ ├─────────────┼─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┤ │ Maturity │ Beta │ ├─────────────┼─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┤ │ Description │ A database sharding router for simple sharding │ ├─────────────┼─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┤ │ Parameters │ [ │ │ │ { │ │ │ "default_value": false, │ │ │ "description": "Enable debug mode", │ │ │ "mandatory": false, │ │ │ "modifiable": true, │ │ │ "name": "debug", │ │ │ "type": "bool" │ │ │ }, │ │ │ { │ │ │ "default_value": [], │ │ │ "description": "List of tables to ignore when checking for duplicates", │ │ │ "mandatory": false, │ │ │ "modifiable": true, │ │ │ "name": "ignore_tables", │ │ │ "type": "stringlist" │ │ │ }, │ │ │ { │ │ │ "description": "Regex of tables to ignore when checking for duplicates", │ │ │ "mandatory": false, │ │ │ "modifiable": true, │ │ │ "name": "ignore_tables_regex", │ │ │ "type": "regex" │ │ │ }, │ │ │ { │ │ │ "default_value": "150000ms", │ │ │ "description": "Maximum allowed staleness of a database map entry before clients block and wait for an update", │ │ │ "mandatory": false, │ │ │ "modifiable": true, │ │ │ "name": "max_staleness", │ │ │ "type": "duration", │ │ │ "unit": "ms" │ │ │ }, │ │ │ { │ │ │ "default_value": false, │ │ │ "description": "Refresh database mapping information", │ │ │ "mandatory": false, │ │ │ "modifiable": true, │ │ │ "name": "refresh_databases", │ │ │ "type": "bool" │ │ │ }, │ │ │ { │ │ │ "default_value": "300000ms", │ │ │ "description": "How often to refresh the database mapping information", │ │ │ "mandatory": false, │ │ │ "modifiable": true, │ │ │ "name": "refresh_interval", │ │ │ "type": "duration", │ │ │ "unit": "ms" │ │ │ }, │ │ │ { │ │ │ "default_value": false, │ │ │ "description": "Retrieve users from all backend servers instead of only one", │ │ │ "mandatory": false, │ │ │ "modifiable": true, │ │ │ "name": "auth_all_servers", │ │ │ "type": "bool" │ │ │ }, │ │ │ { │ │ │ "default_value": "300000ms", │ │ │ "description": "How ofted idle connections are pinged", │ │ │ "mandatory": false, │ │ │ "modifiable": true, │ │ │ "name": "connection_keepalive", │ │ │ "type": "duration", │ │ │ "unit": "ms" │ │ │ }, │ │ │ { │ │ │ "deprecated": true, │ │ │ "description": "Alias for 'wait_timeout'", │ │ │ "mandatory": false, │ │ │ "modifiable": true, │ │ │ "name": "connection_timeout", │ │ │ "type": "duration" │ │ │ }, │ │ │ { │ │ │ "default_value": false, │ │ │ "description": "Disable session command history", │ │ │ "mandatory": false, │ │ │ "modifiable": true, │ │ │ "name": "disable_sescmd_history", │ │ │ "type": "bool" │ │ │ }, │ │ │ { │ │ │ "default_value": false, │ │ │ "description": "Allow the root user to connect to this service", │ │ │ "mandatory": false, │ │ │ "modifiable": true, │ │ │ "name": "enable_root_user", │ │ │ "type": "bool" │ │ │ }, │ │ │ { │ │ │ "default_value": false, │ │ │ "description": "Ping connections unconditionally", │ │ │ "mandatory": false, │ │ │ "modifiable": true, │ │ │ "name": "force_connection_keepalive", │ │ │ "type": "bool" │ │ │ }, │ │ │ { │ │ │ "default_value": "-1ms", │ │ │ "description": "Put connections into pool after session has been idle for this long", │ │ │ "mandatory": false, │ │ │ "modifiable": true, │ │ │ "name": "idle_session_pool_time", │ │ │ "type": "duration", │ │ │ "unit": "ms" │ │ │ }, │ │ │ { │ │ │ "default_value": true, │ │ │ "description": "Match localhost to wildcard host", │ │ │ "mandatory": false, │ │ │ "modifiable": true, │ │ │ "name": "localhost_match_wildcard_host", │ │ │ "type": "bool" │ │ │ }, │ │ │ { │ │ │ "default_value": true, │ │ │ "description": "Log a warning when client authentication fails", │ │ │ "mandatory": false, │ │ │ "modifiable": true, │ │ │ "name": "log_auth_warnings", │ │ │ "type": "bool" │ │ │ }, │ │ │ { │ │ │ "default_value": false, │ │ │ "description": "Log debug messages for this service (debug builds only)", │ │ │ "mandatory": false, │ │ │ "modifiable": true, │ │ │ "name": "log_debug", │ │ │ "type": "bool" │ │ │ }, │ │ │ { │ │ │ "default_value": false, │ │ │ "description": "Log info messages for this service", │ │ │ "mandatory": false, │ │ │ "modifiable": true, │ │ │ "name": "log_info", │ │ │ "type": "bool" │ │ │ }, │ │ │ { │ │ │ "default_value": false, │ │ │ "description": "Log notice messages for this service", │ │ │ "mandatory": false, │ │ │ "modifiable": true, │ │ │ "name": "log_notice", │ │ │ "type": "bool" │ │ │ }, │ │ │ { │ │ │ "default_value": false, │ │ │ "description": "Log warning messages for this service", │ │ │ "mandatory": false, │ │ │ "modifiable": true, │ │ │ "name": "log_warning", │ │ │ "type": "bool" │ │ │ }, │ │ │ { │ │ │ "default_value": 0, │ │ │ "description": "Maximum number of connections", │ │ │ "mandatory": false, │ │ │ "modifiable": true, │ │ │ "name": "max_connections", │ │ │ "type": "count" │ │ │ }, │ │ │ { │ │ │ "default_value": 50, │ │ │ "description": "Session command history size", │ │ │ "mandatory": false, │ │ │ "modifiable": true, │ │ │ "name": "max_sescmd_history", │ │ │ "type": "count" │ │ │ }, │ │ │ { │ │ │ "default_value": "60000ms", │ │ │ "description": "How long a session can wait for a connection to become available", │ │ │ "mandatory": false, │ │ │ "modifiable": true, │ │ │ "name": "multiplex_timeout", │ │ │ "type": "duration", │ │ │ "unit": "ms" │ │ │ }, │ │ │ { │ │ │ "default_value": "0ms", │ │ │ "description": "Network write timeout", │ │ │ "mandatory": false, │ │ │ "modifiable": true, │ │ │ "name": "net_write_timeout", │ │ │ "type": "duration", │ │ │ "unit": "ms" │ │ │ }, │ │ │ { │ │ │ "description": "Password for the user used to retrieve database users", │ │ │ "mandatory": true, │ │ │ "modifiable": true, │ │ │ "name": "password", │ │ │ "type": "password" │ │ │ }, │ │ │ { │ │ │ "default_value": true, │ │ │ "description": "Prune old session command history if the limit is exceeded", │ │ │ "mandatory": false, │ │ │ "modifiable": true, │ │ │ "name": "prune_sescmd_history", │ │ │ "type": "bool" │ │ │ }, │ │ │ { │ │ │ "default_value": "primary", │ │ │ "description": "Service rank", │ │ │ "enum_values": [ │ │ │ "primary", │ │ │ "secondary" │ │ │ ], │ │ │ "mandatory": false, │ │ │ "modifiable": true, │ │ │ "name": "rank", │ │ │ "type": "enum" │ │ │ }, │ │ │ { │ │ │ "default_value": -1, │ │ │ "description": "Number of statements kept in memory", │ │ │ "mandatory": false, │ │ │ "modifiable": true, │ │ │ "name": "retain_last_statements", │ │ │ "type": "int" │ │ │ }, │ │ │ { │ │ │ "default_value": false, │ │ │ "description": "Enable session tracing for this service", │ │ │ "mandatory": false, │ │ │ "modifiable": true, │ │ │ "name": "session_trace", │ │ │ "type": "bool" │ │ │ }, │ │ │ { │ │ │ "default_value": false, │ │ │ "deprecated": true, │ │ │ "description": "Track session state using server responses", │ │ │ "mandatory": false, │ │ │ "modifiable": true, │ │ │ "name": "session_track_trx_state", │ │ │ "type": "bool" │ │ │ }, │ │ │ { │ │ │ "default_value": true, │ │ │ "deprecated": true, │ │ │ "description": "Strip escape characters from database names", │ │ │ "mandatory": false, │ │ │ "modifiable": true, │ │ │ "name": "strip_db_esc", │ │ │ "type": "bool" │ │ │ }, │ │ │ { │ │ │ "description": "Username used to retrieve database users", │ │ │ "mandatory": true, │ │ │ "modifiable": true, │ │ │ "name": "user", │ │ │ "type": "string" │ │ │ }, │ │ │ { │ │ │ "description": "Load additional users from a file", │ │ │ "mandatory": false, │ │ │ "modifiable": false, │ │ │ "name": "user_accounts_file", │ │ │ "type": "path" │ │ │ }, │ │ │ { │ │ │ "default_value": "add_when_load_ok", │ │ │ "description": "When and how the user accounts file is used", │ │ │ "enum_values": [ │ │ │ "add_when_load_ok", │ │ │ "file_only_always" │ │ │ ], │ │ │ "mandatory": false, │ │ │ "modifiable": false, │ │ │ "name": "user_accounts_file_usage", │ │ │ "type": "enum" │ │ │ }, │ │ │ { │ │ │ "description": "Custom version string to use", │ │ │ "mandatory": false, │ │ │ "modifiable": true, │ │ │ "name": "version_string", │ │ │ "type": "string" │ │ │ }, │ │ │ { │ │ │ "default_value": "0ms", │ │ │ "description": "Connection idle timeout", │ │ │ "mandatory": false, │ │ │ "modifiable": true, │ │ │ "name": "wait_timeout", │ │ │ "type": "duration", │ │ │ "unit": "ms" │ │ │ } │ │ │ ] │ ├─────────────┼─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┤ │ Commands │ [ │ │ │ { │ │ │ "attributes": { │ │ │ "arg_max": 1, │ │ │ "arg_min": 1, │ │ │ "description": "Clear schemarouter shard map cache", │ │ │ "method": "POST", │ │ │ "parameters": [ │ │ │ { │ │ │ "description": "The schemarouter service", │ │ │ "required": true, │ │ │ "type": "SERVICE" │ │ │ } │ │ │ ] │ │ │ }, │ │ │ "id": "clear", │ │ │ "links": { │ │ │ "self": "http://127.0.0.1:8989/v1/modules/schemarouter/clear/" │ │ │ }, │ │ │ "type": "module_command" │ │ │ }, │ │ │ { │ │ │ "attributes": { │ │ │ "arg_max": 1, │ │ │ "arg_min": 1, │ │ │ "description": "Invalidate schemarouter shard map cache", │ │ │ "method": "POST", │ │ │ "parameters": [ │ │ │ { │ │ │ "description": "The schemarouter service", │ │ │ "required": true, │ │ │ "type": "SERVICE" │ │ │ } │ │ │ ] │ │ │ }, │ │ │ "id": "invalidate", │ │ │ "links": { │ │ │ "self": "http://127.0.0.1:8989/v1/modules/schemarouter/invalidate/" │ │ │ }, │ │ │ "type": "module_command" │ │ │ } │ │ │ ] │ └─────────────┴─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┘ shell> maxctrl show commands schemarouter ┌────────────┬────────────┬──────────────────────────┐ │ Command │ Parameters │ Descriptions │ ├────────────┼────────────┼──────────────────────────┤ │ clear │ SERVICE │ The schemarouter service │ ├────────────┼────────────┼──────────────────────────┤ │ invalidate │ SERVICE │ The schemarouter service │ └────────────┴────────────┴──────────────────────────┘ shell> maxctrl show dbusers Sharded-Service ┌───────────────────────┬────────────────┬───────────────────────┬───────┬───────┬────────┬───────┬──────┐ │ User │ Host │ Plugin │ TLS │ Super │ Global │ Proxy │ Role │ ├───────────────────────┼────────────────┼───────────────────────┼───────┼───────┼────────┼───────┼──────┤ │ PUBLIC │ │ │ false │ false │ false │ false │ │ ├───────────────────────┼────────────────┼───────────────────────┼───────┼───────┼────────┼───────┼──────┤ │ app │ 10.139.158.% │ mysql_native_password │ false │ false │ false │ false │ │ ├───────────────────────┼────────────────┼───────────────────────┼───────┼───────┼────────┼───────┼──────┤ │ app_role │ │ │ false │ false │ false │ false │ │ ├───────────────────────┼────────────────┼───────────────────────┼───────┼───────┼────────┼───────┼──────┤ │ mariadb.sys │ localhost │ mysql_native_password │ false │ false │ false │ false │ │ ├───────────────────────┼────────────────┼───────────────────────┼───────┼───────┼────────┼───────┼──────┤ │ maxscale_admin │ 10.139.158.210 │ mysql_native_password │ false │ false │ false │ false │ │ ├───────────────────────┼────────────────┼───────────────────────┼───────┼───────┼────────┼───────┼──────┤ │ maxscale_admin │ 10.139.158.211 │ mysql_native_password │ false │ false │ false │ false │ │ ├───────────────────────┼────────────────┼───────────────────────┼───────┼───────┼────────┼───────┼──────┤ │ maxscale_admin_role │ │ │ false │ false │ false │ false │ │ ├───────────────────────┼────────────────┼───────────────────────┼───────┼───────┼────────┼───────┼──────┤ │ maxscale_monitor │ 10.139.158.210 │ mysql_native_password │ false │ false │ false │ false │ │ ├───────────────────────┼────────────────┼───────────────────────┼───────┼───────┼────────┼───────┼──────┤ │ maxscale_monitor │ 10.139.158.211 │ mysql_native_password │ false │ false │ false │ false │ │ ├───────────────────────┼────────────────┼───────────────────────┼───────┼───────┼────────┼───────┼──────┤ │ maxscale_monitor_role │ │ │ false │ false │ false │ false │ │ ├───────────────────────┼────────────────┼───────────────────────┼───────┼───────┼────────┼───────┼──────┤ │ mysql │ localhost │ mysql_native_password │ false │ true │ true │ false │ │ ├───────────────────────┼────────────────┼───────────────────────┼───────┼───────┼────────┼───────┼──────┤ │ root │ localhost │ mysql_native_password │ false │ true │ true │ false │ │ └───────────────────────┴────────────────┴───────────────────────┴───────┴───────┴────────┴───────┴──────┘ shell> maxctrl show commands mariadbmon ┌───────────────────────────┬─────────────────────────────┬───────────────────────────────────────────────────────────────────────────────┐ │ Command │ Parameters │ Descriptions │ ├───────────────────────────┼─────────────────────────────┼───────────────────────────────────────────────────────────────────────────────┤ │ switchover │ MONITOR, [SERVER], [SERVER] │ Monitor name, New primary (optional), Current primary (optional) │ ├───────────────────────────┼─────────────────────────────┼───────────────────────────────────────────────────────────────────────────────┤ │ switchover-force │ MONITOR, [SERVER], [SERVER] │ Monitor name, New primary (optional), Current primary (optional) │ ├───────────────────────────┼─────────────────────────────┼───────────────────────────────────────────────────────────────────────────────┤ │ async-switchover │ MONITOR, [SERVER], [SERVER] │ Monitor name, New primary (optional), Current primary (optional) │ ├───────────────────────────┼─────────────────────────────┼───────────────────────────────────────────────────────────────────────────────┤ │ failover │ MONITOR │ Monitor name │ ├───────────────────────────┼─────────────────────────────┼───────────────────────────────────────────────────────────────────────────────┤ │ async-failover │ MONITOR │ Monitor name │ ├───────────────────────────┼─────────────────────────────┼───────────────────────────────────────────────────────────────────────────────┤ │ rejoin │ MONITOR, SERVER │ Monitor name, Joining server │ ├───────────────────────────┼─────────────────────────────┼───────────────────────────────────────────────────────────────────────────────┤ │ async-rejoin │ MONITOR, SERVER │ Monitor name, Joining server │ ├───────────────────────────┼─────────────────────────────┼───────────────────────────────────────────────────────────────────────────────┤ │ reset-replication │ MONITOR, [SERVER] │ Monitor name, Primary server (optional) │ ├───────────────────────────┼─────────────────────────────┼───────────────────────────────────────────────────────────────────────────────┤ │ async-reset-replication │ MONITOR, [SERVER] │ Monitor name, Primary server (optional) │ ├───────────────────────────┼─────────────────────────────┼───────────────────────────────────────────────────────────────────────────────┤ │ release-locks │ MONITOR │ Monitor name │ ├───────────────────────────┼─────────────────────────────┼───────────────────────────────────────────────────────────────────────────────┤ │ async-release-locks │ MONITOR │ Monitor name │ ├───────────────────────────┼─────────────────────────────┼───────────────────────────────────────────────────────────────────────────────┤ │ fetch-cmd-result │ MONITOR │ Monitor name │ ├───────────────────────────┼─────────────────────────────┼───────────────────────────────────────────────────────────────────────────────┤ │ cancel-cmd │ MONITOR │ Monitor name │ ├───────────────────────────┼─────────────────────────────┼───────────────────────────────────────────────────────────────────────────────┤ │ async-cs-add-node │ MONITOR, STRING, STRING │ Monitor name, Hostname/IP of node to add to ColumnStore cluster, Timeout │ ├───────────────────────────┼─────────────────────────────┼───────────────────────────────────────────────────────────────────────────────┤ │ async-cs-remove-node │ MONITOR, STRING, STRING │ Monitor name, Hostname/IP of node to remove from ColumnStore cluster, Timeout │ ├───────────────────────────┼─────────────────────────────┼───────────────────────────────────────────────────────────────────────────────┤ │ cs-get-status │ MONITOR │ Monitor name │ ├───────────────────────────┼─────────────────────────────┼───────────────────────────────────────────────────────────────────────────────┤ │ async-cs-get-status │ MONITOR │ Monitor name │ ├───────────────────────────┼─────────────────────────────┼───────────────────────────────────────────────────────────────────────────────┤ │ async-cs-start-cluster │ MONITOR, STRING │ Monitor name, Timeout │ ├───────────────────────────┼─────────────────────────────┼───────────────────────────────────────────────────────────────────────────────┤ │ async-cs-stop-cluster │ MONITOR, STRING │ Monitor name, Timeout │ ├───────────────────────────┼─────────────────────────────┼───────────────────────────────────────────────────────────────────────────────┤ │ async-cs-set-readonly │ MONITOR, STRING │ Monitor name, Timeout │ ├───────────────────────────┼─────────────────────────────┼───────────────────────────────────────────────────────────────────────────────┤ │ async-cs-set-readwrite │ MONITOR, STRING │ Monitor name, Timeout │ ├───────────────────────────┼─────────────────────────────┼───────────────────────────────────────────────────────────────────────────────┤ │ async-rebuild-server │ MONITOR, SERVER, [SERVER] │ Monitor name, Target server, Source server (optional) │ ├───────────────────────────┼─────────────────────────────┼───────────────────────────────────────────────────────────────────────────────┤ │ async-create-backup │ MONITOR, SERVER, STRING │ Monitor name, Source server, Backup name │ ├───────────────────────────┼─────────────────────────────┼───────────────────────────────────────────────────────────────────────────────┤ │ async-restore-from-backup │ MONITOR, SERVER, STRING │ Monitor name, Target server, Backup name │ └───────────────────────────┴─────────────────────────────┴───────────────────────────────────────────────────────────────────────────────┘
Literature / Sources
Taxonomy upgrade extras: shardingmaxscaleschemarouterload balancermulti-tenant

Sharding mit MariaDB MaxScale

Oli Sennhauser - Mon, 2024-03-18 16:08
Inhaltsverzeichnis
Übersicht

Dieses Feature sollte mehr oder weniger mit MariaDB MaxScale 6 (2.6), 6.1 bis 6.4 und 22.08 (6.5), 23.02 (7.0) und 23.08 (7.1) funktionieren. Wir haben es mit der neusten MaxScale Version 23.08.05 getestet, da wir mit einer älteren Version auf Problem gestossen sind.

shell> maxscale --version MaxScale 23.08.5

Als Datenbank Backend (Shards) haben wir MariaDB 10.11 verwendet.

Weniger als ca 2% aller uns bekannten MariaDB Installationen sind das, was wir technische unter Multi-Mandanten-Systeme (multi-tenant systems) verstehen (jeder Mandant (Kunde) in einer eigenen Datenbank (auch Schema genannt)).

Daher wird dieses MariaDB MaxScale Feature relativ selten genutzt und es besteht die erhöhte Gefahr auf Bugs zu stossen, auf welche vorher noch niemand gestossen ist!

Dieses Feature wird bei MariadDB MaxScale: SchemaRouter genannt und wird immer noch als Beta-Qualität deklariert:

maxctrl> show module schemarouter ┌─────────────┬────────────────────────────────────────────────┐ │ Module │ schemarouter │ ├─────────────┼────────────────────────────────────────────────┤ │ Type │ Router │ ├─────────────┼────────────────────────────────────────────────┤ │ Version │ V1.0.0 │ ├─────────────┼────────────────────────────────────────────────┤ │ Maturity │ Beta │ ├─────────────┼────────────────────────────────────────────────┤ │ Description │ A database sharding router for simple sharding │ ├─────────────┼────────────────────────────────────────────────┤ │ ...

Die Ziel-Topologie soll wie folgt aussehen: Jeder Kunde (Mandant, Tenant) liegt in einer eigenen Datenbank (= Schema). Die Datenbanken sind über mehrere MariaDB Instanzen (Shards) verteilt. Damit die Applikation transparent auf die Datenbank zugreifen kann wird ein Pärchen MaxScale Load Balancer davor geschaltet, welches weiss, wo der Kunde liegt und den Traffic entsprechend an das Shard weiterleitet. Damit die MaxScale Load Balancer hochverfügbar ausgelegt sind, wird noch eine virtuelle IP (VIP) z.B. mittels Keepalived vorgeschaltet. Wem das noch zu einfach ist, der kann jedes einzelne Shard noch als Master/Slave- oder Galera Cluster-Konstrukt auslegen...

Vorbereitung der Shards (MariaDB Datenbank Instanzen)

Als erstes hatten wir bei diesem PoC Problem mit der test Datenbank. Durch das Löschen der test Datenbank auf allen Shards ist das Problem verschwunden. Alternativ dazu kann man mariadb-secure-installation ausführen, was man auf Produktionsystemen sowieso machen sollte, oder man nutzt die MaxScale Konfigurationsparameter: ignore_tables oder ignore_tables_regex um gleiche Tabellen in unterschiedlichen Shards zu erlauben.

Siehe auch: MaxScale Router Parameters.

Testdaten erstellen

Damit wir was zum Spielen haben, haben wir uns Testdaten erstellt:

-- Auf Shard 1: 2 Kunden SQL> CREATE DATABASE customer_0010; SQL> CREATE TABLE customer_0010.address (id INT UNSIGNED, name VARCHAR(255)); SQL> CREATE TABLE customer_0010.sales (id INT UNSIGNED, product VARCHAR(255), sales TINYINT, amount DECIMAL(6, 2), total_amount DECIMAL(6, 2)); SQL> INSERT INTO customer_0010.address VALUES (1, 'Customer 10 GmbH'); SQL> INSERT INTO customer_0010.sales VALUES (1, 'Apples', 5, 1.2, 6), (2, 'Pears', 2, 0.9, 1.8), (3, 'Bread', 1, 2.5, 2.5); SQL> CREATE DATABASE customer_0011; SQL> CREATE TABLE customer_0011.address (id INT UNSIGNED, name VARCHAR(255)); SQL> CREATE TABLE customer_0011.sales (id INT UNSIGNED, product VARCHAR(255), sales TINYINT, amount DECIMAL(6, 2), total_amount DECIMAL(6, 2)); SQL> INSERT INTO customer_0011.address VALUES (1, 'Customer 11 SE'); SQL> INSERT INTO customer_0011.sales VALUES (1, 'Oranges', 2, 1.7, 3.4), (2, 'Salat', 5, 1.2, 6); -- Auf Shard 2: 3 Kunden SQL> CREATE DATABASE customer_0020; SQL> CREATE TABLE customer_0020.address (id INT UNSIGNED, name VARCHAR(255)); SQL> CREATE TABLE customer_0020.sales (id INT UNSIGNED, product VARCHAR(255), sales TINYINT, amount DECIMAL(6, 2), total_amount DECIMAL(6, 2)); SQL> INSERT INTO customer_0020.address VALUES (1, 'Customer 20 AG'); SQL> INSERT INTO customer_0020.sales VALUES (1, 'Oranges', 2, 1.7, 3.4), (2, 'Salat', 5, 1.2, 6); SQL> CREATE DATABASE customer_0021; SQL> CREATE TABLE customer_0021.address (id INT UNSIGNED, name VARCHAR(255)); SQL> CREATE TABLE customer_0021.sales (id INT UNSIGNED, product VARCHAR(255), sales TINYINT, amount DECIMAL(6, 2), total_amount DECIMAL(6, 2)); SQL> INSERT INTO customer_0021.address VALUES (1, 'Customer 21 GmbH'); SQL> INSERT INTO customer_0021.sales VALUES (1, 'Oranges', 2, 1.7, 3.4), (2, 'Salat', 5, 1.2, 6); SQL> CREATE DATABASE customer_0022; SQL> CREATE TABLE customer_0022.address (id INT UNSIGNED, name VARCHAR(255)); SQL> CREATE TABLE customer_0022.sales (id INT UNSIGNED, product VARCHAR(255), sales TINYINT, amount DECIMAL(6, 2), total_amount DECIMAL(6, 2)); SQL> INSERT INTO customer_0022.address VALUES (1, 'Customer 22 Gebr.'); SQL> INSERT INTO customer_0022.sales VALUES (1, 'Oranges', 2, 1.7, 3.4), (2, 'Salat', 5, 1.2, 6); -- Auf Shard 3: 1 Kunde SQL> CREATE DATABASE customer_0030; SQL> CREATE TABLE customer_0030.address (id INT UNSIGNED, name VARCHAR(255)); SQL> CREATE TABLE customer_0030.sales (id INT UNSIGNED, product VARCHAR(255), sales TINYINT, amount DECIMAL(6, 2), total_amount DECIMAL(6, 2)); SQL> INSERT INTO customer_0030.address VALUES (1, 'Customer 30 GmbH'); SQL> INSERT INTO customer_0030.sales VALUES (1, 'Pickles', 2, 2.2, 4.4), (2, 'Salat', 1, 3.1, 3.1), (3, 'Pudding', 5, 2.2, 11.0), (4, 'Asparagus', 12, .3, 3.6);
Rollen und User erstellen

Da in einem geshardeten System, im Unterschied zum Beispiel zu einem Galera Cluster, die einzelnen Datenbank-Instanzen nichts voneinander wissen und nicht miteinander kommunizieren, müssen wir die Rollen und User bzw. Accounts jeweils auf JEDEM Shard einzeln anlegen.

MariaDB MaxScale braucht jeweils für den SchemaRouter Service und den Monitor einen User (auf jedem Shard).

Der Monitor User ist, wie der Name sagt fürs Monitoring zuständig und der SchemaRouter Service User um die User Account Informationen aus den Sharding-Backends einzusammeln und die Queries an das richtige Shard weiterzuleiten.

Da in einem redundanten System typischerweise mit mindestens zwei MaxScale Routern gearbeitet wird und wir dem auseinanderlaufen der Privilegien der Accounts vorbeugen wollten arbeiten wir mit Rollen sowohl für die MaxScale User als auch die applikatorischen User.

MaxScale Monitor User SQL> CREATE ROLE maxscale_monitor_role; SQL> GRANT SELECT ON mysql.user TO 'maxscale_monitor_role'; SQL> GRANT REPLICATION CLIENT ON *.* TO 'maxscale_monitor_role'; SQL> GRANT SLAVE MONITOR ON *.* TO 'maxscale_monitor_role'; SQL> GRANT FILE ON *.* TO 'maxscale_monitor_role'; SQL> GRANT CONNECTION ADMIN ON *.* TO 'maxscale_monitor_role'; SQL> SHOW GRANTS FOR maxscale_monitor_role; +-----------------------------------------------------------------------------------------------+ | Grants for maxscale_monitor_role | +-----------------------------------------------------------------------------------------------+ | GRANT FILE, BINLOG MONITOR, CONNECTION ADMIN, SLAVE MONITOR ON *.* TO `maxscale_monitor_role` | | GRANT SELECT ON `mysql`.`user` TO `maxscale_monitor_role` | +-----------------------------------------------------------------------------------------------+ SQL> CREATE USER maxscale_monitor@'10.139.158.210' IDENTIFIED BY 'secret'; SQL> CREATE USER maxscale_monitor@'10.139.158.211' IDENTIFIED BY 'secret'; SQL> GRANT maxscale_monitor_role TO maxscale_monitor@'10.139.158.210'; SQL> GRANT maxscale_monitor_role TO maxscale_monitor@'10.139.158.211'; SQL> SET DEFAULT ROLE maxscale_monitor_role FOR maxscale_monitor@'10.139.158.210'; SQL> SET DEFAULT ROLE maxscale_monitor_role FOR maxscale_monitor@'10.139.158.211'; SQL> SELECT user, host, is_role, default_role FROM mysql.user WHERE user LIKE 'maxscale_monitor%'; +-----------------------+----------------+---------+-----------------------+ | User | Host | is_role | default_role | +-----------------------+----------------+---------+-----------------------+ | maxscale_monitor_role | | Y | | | maxscale_monitor | 10.139.158.210 | N | maxscale_monitor_role | | maxscale_monitor | 10.139.158.211 | N | maxscale_monitor_role | +-----------------------+----------------+---------+-----------------------+ SQL> SHOW GRANTS FOR maxscale_monitor@'10.139.158.211'; +------------------------------------------------------------------------------------------------------------------------------+ | Grants for maxscale_monitor@10.139.158.211 | +------------------------------------------------------------------------------------------------------------------------------+ | GRANT `maxscale_monitor_role` TO `maxscale_monitor`@`10.139.158.211` | | GRANT USAGE ON *.* TO `maxscale_monitor`@`10.139.158.211` IDENTIFIED BY PASSWORD '*14E65567ABDB5135D0CFD9A70B3032C179A49EE7' | | SET DEFAULT ROLE `maxscale_monitor_role` FOR `maxscale_monitor`@`10.139.158.211` | +------------------------------------------------------------------------------------------------------------------------------+
MaxScale Admin User SQL> CREATE ROLE maxscale_admin_role; SQL> GRANT SHOW DATABASES ON *.* TO 'maxscale_admin_role'; SQL> GRANT SELECT ON mysql.user TO 'maxscale_admin_role'; SQL> GRANT SELECT ON mysql.db TO 'maxscale_admin_role'; SQL> GRANT SELECT ON mysql.tables_priv TO 'maxscale_admin_role'; SQL> GRANT SELECT ON mysql.columns_priv TO 'maxscale_admin_role'; SQL> GRANT SELECT ON mysql.proxies_priv TO 'maxscale_admin_role'; SQL> GRANT SELECT ON mysql.roles_mapping TO 'maxscale_admin_role'; SQL> GRANT SELECT ON mysql.procs_priv TO 'maxscale_admin_role'; SQL> SHOW GRANTS FOR maxscale_admin_role; +------------------------------------------------------------------+ | Grants for maxscale_admin_role | +------------------------------------------------------------------+ | GRANT USAGE ON *.* TO `maxscale_admin_role` | | GRANT SELECT ON `mysql`.`user` TO `maxscale_admin_role` | | GRANT SELECT ON `mysql`.`roles_mapping` TO `maxscale_admin_role` | | GRANT SELECT ON `mysql`.`tables_priv` TO `maxscale_admin_role` | | GRANT SELECT ON `mysql`.`procs_priv` TO `maxscale_admin_role` | | GRANT SELECT ON `mysql`.`db` TO `maxscale_admin_role` | | GRANT SELECT ON `mysql`.`columns_priv` TO `maxscale_admin_role` | | GRANT SELECT ON `mysql`.`proxies_priv` TO `maxscale_admin_role` | +------------------------------------------------------------------+ SQL> CREATE USER maxscale_admin@'10.139.158.210' IDENTIFIED BY 'secret'; SQL> CREATE USER maxscale_admin@'10.139.158.211' IDENTIFIED BY 'secret'; SQL> GRANT maxscale_admin_role TO maxscale_admin@'10.139.158.210'; SQL> GRANT maxscale_admin_role TO maxscale_admin@'10.139.158.211'; SQL> SET DEFAULT ROLE maxscale_admin_role FOR maxscale_admin@'10.139.158.210'; SQL> SET DEFAULT ROLE maxscale_admin_role FOR maxscale_admin@'10.139.158.211'; SQL> SELECT user, host, is_role, default_role FROM mysql.user WHERE user LIKE 'maxscale_admin%'; +---------------------+----------------+---------+---------------------+ | User | Host | is_role | default_role | +---------------------+----------------+---------+---------------------+ | maxscale_admin_role | | Y | | | maxscale_admin | 10.139.158.210 | N | maxscale_admin_role | | maxscale_admin | 10.139.158.211 | N | maxscale_admin_role | +---------------------+----------------+---------+---------------------+ SQL> SHOW GRANTS FOR maxscale_admin@'10.139.158.211'; +----------------------------------------------------------------------------------------------------------------------------+ | Grants for maxscale_admin@10.139.158.211 | +----------------------------------------------------------------------------------------------------------------------------+ | GRANT `maxscale_admin_role` TO `maxscale_admin`@`10.139.158.211` | | GRANT USAGE ON *.* TO `maxscale_admin`@`10.139.158.211` IDENTIFIED BY PASSWORD '*14E65567ABDB5135D0CFD9A70B3032C179A49EE7' | | SET DEFAULT ROLE `maxscale_admin_role` FOR `maxscale_admin`@`10.139.158.211` | +----------------------------------------------------------------------------------------------------------------------------+

Siehe dazu auch: SchemaRouter Configuration

Applikationsrolle und Accounts erstellen

Für die Applikation braucht es ebenfalls einen User, den wir hier wie auf jedem Shard wie folgt erstellen:

SQL> CREATE ROLE app_role; SQL> GRANT SELECT, INSERT, UPDATE, DELETE ON `customer_%`.* TO 'app_role'; SQL> GRANT SHOW DATABASES ON *.* TO 'app_role'; SQL> GRANT CREATE, DROP, ALTER ON *.* TO 'app_role'; -- For creating new tenant databases SQL> SHOW GRANTS FOR app_role; +----------------------------------------------------------------------+ | Grants for app_role | +----------------------------------------------------------------------+ | GRANT SHOW DATABASES ON *.* TO `app_role` | | GRANT SELECT, INSERT, UPDATE, DELETE ON `customer_%`.* TO `app_role` | +----------------------------------------------------------------------+ SQL> CREATE USER app@'10.139.158.%' IDENTIFIED BY 'secret'; SQL> GRANT app_role TO app@'10.139.158.%'; SQL> SET DEFAULT ROLE app_role FOR app@'10.139.158.%'; SQL> SELECT user, host, is_role, default_role FROM mysql.user WHERE user LIKE 'app%'; +----------+--------------+---------+--------------+ | User | Host | is_role | default_role | +----------+--------------+---------+--------------+ | app_role | | Y | | | app | 10.139.158.% | N | app_role | +----------+--------------+---------+--------------+ SQL> SHOW GRANTS FOR app@'10.139.158.%'; +---------------------------------------------------------------------------------------------------------------+ | Grants for app@10.139.158.% | +---------------------------------------------------------------------------------------------------------------+ | GRANT `app_role` TO `app`@`10.139.158.%` | | GRANT USAGE ON *.* TO `app`@`10.139.158.%` IDENTIFIED BY PASSWORD '*14E65567ABDB5135D0CFD9A70B3032C179A49EE7' | | SET DEFAULT ROLE `app_role` FOR `app`@`10.139.158.%` | +---------------------------------------------------------------------------------------------------------------+
Proxy Protokoll

Load Balancer und Proxies haben die Eigenschaft, dass sie die IP Adressen der Clients durch ihre eigenen IP Adressen austauschen. Dies führt einerseits dazu, dass man auf der Datenbank nicht mehr sieht, woher der Client ursprünglich kommt, andererseits kann man die Zugriffsberechtigungen nicht mehr auf User und IP vergeben, da immer gegen die IP der Load Balancer geprüft wird.

Diese beiden Probleme können mittels des Proxy Protokolls gelöst werden.

Hierzu müssen einerseits die Datenbank und andererseits die Load Balancer, in diesem Fall der MaxScale, das Proxy Protokoll aktiviert haben.

Auf der Datenbank-Seite aktiviert man das Proxy Protokoll wie folgt:

# # my.cnf # [mariadbd] proxy_protocol_networks = ::1, 10.139.158.0/24, localhost

und auf MaxScale-Seite mit:

# # /etc/maxscale.cnf # [shard<n>] type = server proxy_protocol = true

Überprüfen kann man die beiden Einstellungen mit:

SQL> SHOW GLOBAL VARIABLES LIKE 'proxy%'; +-------------------------+---------------------------------+ | Variable_name | Value | +-------------------------+---------------------------------+ | proxy_protocol_networks | ::1, 10.139.158.0/24, localhost | +-------------------------+---------------------------------+ shell> maxctrl show server shard1 | grep proxy │ │ "proxy_protocol": true, │

Quellen:


MaxScale SchemaRouter Konfiguration

Als nächstes bereiten wir die MaxScale Konfiguration fürs Sharding vor. Die von MariaDB empfohlene Datei ist /etc/maxscale.cnf. Ob es sinnvoller ist eine eigene Konfigurations-Datei unter /etc/maxscale.cnf.d/ zu erstellen oder gar den ganze MaxScale dynamisch zu konfigurieren (/var/lib/maxscale/maxscale.cnf.d/*.cnf), wird sich langfristig zeigen. Siehe auch Warnungen weiter unten. Die Konfigurationsdatei für dieses Sharding PoC sieht wie folgt aus:

# # /etc/maxscale.cnf # [maxscale] threads = auto admin_gui = false [shard1] type = server address = 10.139.158.1 port = 3363 proxy_protocol = true [shard2] type=server address=10.139.158.1 port=3364 proxy_protocol = true [shard3] type = server address = 10.139.158.1 port = 3365 proxy_protocol = true [Sharding-Monitor] type = monitor module = galeramon servers = shard1,shard2,shard3 user = maxscale_monitor password = secret monitor_interval = 1s [Sharded-Service-Listener] type = listener service = Sharded-Service protocol = MariaDBClient port = 3306 [Sharded-Service] type = service router = schemarouter servers = shard1,shard2,shard3 user = maxscale_admin password = secret auth_all_servers = true

Hinweis: Empfehlung des MaxScale Entwicklers: "One workaround might be to actually use galeramon to monitor the nodes instead of mariadbmon."

Starten und Stoppen des MaxScale Load Balancers

Starten und Stoppen von MaxScale erfolgt wie üblich über SystemD:

shell> systemctl restart maxscale shell> systemctl status maxscale ● maxscale.service - MariaDB MaxScale Database Proxy Loaded: loaded (/lib/systemd/system/maxscale.service; enabled; vendor preset: enabled) Drop-In: /run/systemd/system/service.d └─zzz-lxc-service.conf Active: active (running) since Tue 2024-02-27 09:52:57 UTC; 39s ago Process: 187 ExecStart=/usr/bin/maxscale (code=exited, status=0/SUCCESS) Main PID: 188 (maxscale) Tasks: 10 (limit: 18663) Memory: 4.6M CPU: 150ms CGroup: /system.slice/maxscale.service └─188 /usr/bin/maxscale systemd[1]: Starting MariaDB MaxScale Database Proxy... maxscale[188]: Module 'galeramon' loaded from '/usr/lib/x86_64-linux-gnu/maxscale/libgaleramon.so'. maxscale[188]: Module 'schemarouter' loaded from '/usr/lib/x86_64-linux-gnu/maxscale/libschemarouter.so'. maxscale[188]: Using up to 2.3GiB of memory for query classifier cache systemd[1]: Started MariaDB MaxScale Database Proxy.

Falls es Fehler oder Warnungen gegeben hat, kann man diese im MaxScale Error Log sehen:

shell> grep -v notice /var/log/maxscale/maxscale.log 2024-02-13 16:47:22 MariaDB MaxScale is shut down. ---------------------------------------------------- MariaDB MaxScale /var/log/maxscale/maxscale.log Tue Feb 13 16:47:22 2024 ---------------------------------------------------------------------------- 2024-02-27 09:52:56 warning: Discarding journal file '/var/lib/maxscale/Sharding-Monitor_journal.json'. File is for module 'mariadbmon'. Current module is 'galeramon'. 2024-02-27 09:52:56 warning: [galeramon] Invalid 'wsrep_local_index' on server 'shard1': 18446744073709551615
Applikations-Tests Einfache Applikations-Tests shell> mariadb --user=app --password=secret --host=10.139.158.211 --port=3306 --execute='show databases' +--------------------+ | Database | +--------------------+ | customer_0010 | | customer_0011 | | customer_0020 | | customer_0021 | | customer_0022 | | customer_0030 | | information_schema | | mysql | | performance_schema | | sys | +--------------------+
Neuer Befehl show shards shell> mariadb --user=app --password=secret --host=10.139.158.211 --port=3306 customer_0030 --execute='show shards' | grep customer_00.* | sort | column -t customer_0010.address shard1 customer_0010.sales shard1 customer_0010. shard1 customer_0011.address shard1 customer_0011.sales shard1 customer_0011. shard1 customer_0020.address shard2 customer_0020.sales shard2 customer_0020. shard2 customer_0021.address shard2 customer_0021.sales shard2 customer_0021. shard2 customer_0022.address shard2 customer_0022.sales shard2 customer_0022. shard2 customer_0030.address shard3 customer_0030.sales shard3 customer_0030. shard3

Neue Datenbanken werden nicht sofort angezeigt, sondern erst wenn die gecachten Daten upgedatet wurden (refresh_interval (300s / 5 min)).

Siehe hierzu auch: Custom SQL commands

Allgemeinere Test

Zur Erinnerung:

ShardPortCustomerState #13363customer_001<n>Running #23364customer_002<n>Running #33365customer_003<n>Running #43366customer_004<n>Running
shell> mariadb --user=app --password=secret --host=10.139.158.211 --port=3306 --execute='SELECT @@port' +--------+ | @@port | +--------+ | 3363 | +--------+ shell> mariadb --user=app --password=secret --host=10.139.158.211 --port=3306 --database=customer_0010 --execute='SELECT @@port' +--------+ | @@port | +--------+ | 3363 | +--------+ shell> mariadb --user=app --password=secret --host=10.139.158.211 --port=3306 --database=customer_0020 --execute='SELECT @@port' +--------+ | @@port | +--------+ | 3364 | +--------+ shell> mariadb --user=app --password=secret --host=10.139.158.211 --port=3306 --execute='use customer_0020; SELECT @@port' +--------+ | @@port | +--------+ | 3364 | +--------+ shell> mariadb --user=app --password=secret --host=10.139.158.211 --port=3306 customer_0010 --execute='SELECT @@port' +--------+ | @@port | +--------+ | 3363 | +--------+ shell> mariadb --user=app --password=secret --host=10.139.158.211 --port=3306 customer_0020 --execute='SELECT @@port' +--------+ | @@port | +--------+ | 3364 | +--------+ shell> mariadb --user=app --password=secret --host=10.139.158.211 --port=3306 customer_0030 --execute='SELECT @@port' +--------+ | @@port | +--------+ | 3365 | +--------+
Weniger einfache (Backup-) Test shell> mariadb-dump --user=app --password=secret --host=10.139.158.211 --port=3306 --single-transaction customer_0010 > /tmp/customer_0010.sql shell> echo $? 0 shell> mariadb-dump --user=app --password=secret --host=10.139.158.211 --port=3306 --single-transaction customer_0020 > /tmp/customer_0020.sql shell> echo $? 0 shell> mariadb-dump --user=app --password=secret --host=10.139.158.211 --port=3306 --single-transaction customer_0030 > /tmp/customer_0030.sql shell> echo $? 0 shell> mariadb-dump --user=app --password=secret --host=10.139.158.211 --port=3306 --single-transaction --databases customer_0011 > /tmp/customer_0011.sql shell> echo $? 0 shell> mariadb-dump --user=app --password=secret --host=10.139.158.211 --port=3306 --single-transaction --databases customer_0021 > /tmp/customer_0021.sql shell> echo $? 0 shell> mariadb-dump --user=app --password=secret --host=10.139.158.211 --port=3306 --single-transaction --databases customer_0030 > /tmp/customer_0030.sql shell> echo $? 0 shell> ll /tmp/customer_00*sql -rw-rw-r-- 1 oli oli 2738 Mar 18 12:07 /tmp/customer_0010.sql -rw-rw-r-- 1 oli oli 2904 Mar 18 12:08 /tmp/customer_0011.sql -rw-rw-r-- 1 oli oli 2712 Mar 18 12:08 /tmp/customer_0020.sql -rw-rw-r-- 1 oli oli 2906 Mar 18 12:08 /tmp/customer_0021.sql -rw-rw-r-- 1 oli oli 2964 Mar 18 12:08 /tmp/customer_0030.sql shell> tail -n 1 /tmp/customer_*.sql ==> /tmp/customer_0010.sql <== -- Dump completed on 2024-02-13 14:39:21 ==> /tmp/customer_0011.sql <== -- Dump completed on 2024-02-13 14:39:35 ==> /tmp/customer_0020.sql <== -- Dump completed on 2024-02-13 14:40:15 ==> /tmp/customer_0021.sql <== -- Dump completed on 2024-02-13 14:40:42 ==> /tmp/customer_0030.sql <== -- Dump completed on 2024-02-13 14:40:52 shell> cat /tmp/customer_00*sql | grep -A1 -i insert INSERT INTO `address` VALUES (1,'Customer 10 GmbH'); -- INSERT INTO `sales` VALUES (1,'Apples',5,1.20,6.00), -- INSERT INTO `address` VALUES (1,'Customer 11 SE'); -- INSERT INTO `sales` VALUES (1,'Oranges',2,1.70,3.40), -- INSERT INTO `address` VALUES (1,'Customer 20 AG'); -- INSERT INTO `sales` VALUES (1,'Oranges',2,1.70,3.40), -- INSERT INTO `address` VALUES (1,'Customer 21 GmbH'); -- INSERT INTO `sales` VALUES (1,'Oranges',2,1.70,3.40), -- INSERT INTO `address` VALUES (1,'Customer 30 GmbH'); -- INSERT INTO `sales` VALUES (1,'Pickles',2,2.20,4.40),

In MaxScale 23.08.4 war ein ziemlich übler Bug drin: Ein Rückgabewert von 0 aber keine Daten im Backup!!! Siehe dazu auch die Tickets: MXS-4966: mariadb-dump gets an error dumping schemas und MXS-4947: Tables in information_schema are treated as a normal tables. Symptome des Bugs sehen wie folgt aus:

Error: Couldn't read status information for table address () Error: Couldn't read status information for table sales ()

Daher empfiehlt sich dringend ein Upgrade auf MaxScale 23.08.5.

Komplexere Applikations-Tests

Wir haben noch einen etwas komplexeren Test erstellt (./sharding_test.php), der folgen Queries abarbeitet:

SET NAMES utf8mb4 SHOW DATABASES use customer_<nnnn> START TRANSACTION; SELECT MIN(id) AS first, MAX(id) AS last FROM `sales` INSERT INTO sales (id, product, sales, amount, total_amount) VALUES (%d, '%s', %f, %f, %f) INSERT INTO sales (id, product, sales, amount, total_amount) VALUES (%d, '%s', %f, %f, %f) UPDATE sales SET product = 'Prepare to delete' WHERE id = %d DELETE FROM sales WHERE id = %d COMMIT

Dieser Test lief einwandfrei durch. Die dazu gehörende Kontroll-Abfrage:

SQL> SELECT * FROM customer_0021.sales WHERE id >= (SELECT MAX(id) - 10 FROM customer_0021.sales);

Verschiedene Last-Szenarien können zusätzlich mit db_bench oder dem Acronis perfkit getestet werden. Weitere Informationen dazu siehe hier.

Cross-Shard-Tests

Allensfalls könnte man auf die Idee kommen, Cross-Shard-Queries auszuführen. Dies wird NICHT funktionieren, was ja nicht wirklich erstaunen sollte, da erstens nicht ganz einfach zu implementieren und zweites hier beschrieben:

"Note: As the sharding solution in MaxScale is relatively simple, cross-database queries between two or more shards are not supported."

Quelle: Simple Sharding with Two Servers

und

"USE db1 is routed to the server with db1. If the database is divided to multiple servers, only one server will get the command."

Quelle: SchemaRouter

Hier ein Test mit UNION:

SQL> use customer_0030 Database changed SQL> SELECT * FROM customer_0020.sales UNION SELECT * FROM customer_0030.sales; ERROR 1146 (42S02): Table 'customer_0020.sales' doesn't exist

Und hier noch der Gegenbeweis:

SQL> use customer_0020 Database changed SQL> SELECT * FROM customer_0020.sales UNION SELECT * FROM customer_0030.sales; ERROR 1146 (42S02): Table 'customer_0030.sales' doesn't exist

Und hier noch den Test mit JOIN:

SQL> use customer_0020 SQL> SELECT * FROM customer_0020.sales a JOIN customer_0030.sales b ON a.id = b.id WHERE a.sales > 1 ; ERROR 1146 (42S02): Table 'customer_0030.sales' doesn't exist SQL> use customer_0030 SQL> SELECT * FROM customer_0020.sales a JOIN customer_0030.sales b ON a.id = b.id WHERE a.sales > 1 ; ERROR 1146 (42S02): Table 'customer_0020.sales' doesn't exist
Betrieb eines MaxScale Sharding-Systems

In diesem Kapitel besprechen wir einige Punkte die für den Betrieb eines MariaDB MaxScale Sharding-Systems nützlich sein können.

Do-on-all-shards

Da es immer wieder vorkommen kann, dass O/S oder Datenbank Operationen auf allen Shards ausgeführt werden müssen, wäre es sicher sinnvoll ein Skript zu erstellen, welches reihum, auf allen Shards, den selben Befehl ausführt:

shell> ./do-on-all-shards.sh --sql='SHOW DATABASES'

Ein so geartetes Skript dürfte die Fehlerrate im Betrieb stark reduzieren. Auch Operationen wie das Re-sharding eines Mandanten, wie weiter unten beschrieben, werden sinnvollerweise geskriptet und zentral ausgeführt.

Invalidieren des Database Map Caches

Mit dem Befehlt invalidate kann man den Database Map Cache des MariaDB MaxScale SchemaRouters invalidieren. Dies gibt uns die Möglichkeit, nach dem Hinzufügen oder dem Entfernen von Mandanten den Cache schnell wieder auf einen aktuellen Stand zu bringen.

shell> maxctrl call command schemarouter invalidate Sharded-Service OK

Im unterschied zum Befehl invalidate, bei welchem die Einträge nach dem nächsten refresh_intervall auf den neusten Stand gebracht werden, löscht der Befehl clear die Einträge und ein Remap wird sofort ausgeführt.

Wenn man den Database Map Cache von remote mit einem REST API Call invalidieren möchte, geht das wie folgt:

shell> curl -i -X POST -u api_admin:secret http://10.139.158.211:8989/v1/maxscale/modules/schemarouter/clear?Sharded-Service HTTP/1.1 204 No Content Connection: close Date: Mon, 18 Mar 24 11:49:58 GMT X-Frame-Options: Deny X-XSS-Protection: 1 Referrer-Policy: same-origin Cache-Control: no-cache

Quellen:


Wie ändert man SchemaRouter Variablen dynamisch?

Das refresh_interval spezifiziert die Lebensdauer der Einträge im SchemaRouter Database Map Cache. Der default Wert ist 300 s (5 min). Refresh Interval ist daher, meiner Meinung nach, ein unglücklicher Begriff da es nicht das Intervall zwischen zwei Mappings definiert sondern die Lebzeit der Cache-Einträge (livetime?, timeout?). Sobald der Eintrag gelöscht wurde wir ein neuer Refresh der "Database Map" auf jedem Shard getriggert. Der Befehl sieht aktuell wie folgt aus:

SELECT LOWER(t.table_schema), LOWER(t.table_name) FROM information_schema.tables t UNION ALL SELECT LOWER(s.schema_name), '' FROM information_schema.schemata s

So wie es aussieht reicht ein simpler Connect um den Refresh der Database Map zu triggern.

Der aktuelle Wert für refresh_intervall kann wie folgt abgefragt werden.

shell> maxctrl show service Sharded-Service | grep refresh_interval | awk -F'│' '{ print $3 }' "refresh_interval": "300000ms",

Um den Wert dynamisch zu ändern hilft folgender Befehl:

shell> MAXCTRL_WARNINGS=0 maxctrl alter service Sharded-Service refresh_interval=10s OK

Der Wert sollte nicht zu klein eingestellt werden, da während des Mapping Vorgangs alle anderen Connections angehalten werden.

Quellen:


Hinzufügen und Entfernen eines Mandanten

Das Hinzufügen eines neuen Mandanten zu einem Shard stellt kein grosses Problem dar:

SQL> CREATE DATABASE customer_0029; SQL> use customer_0029 SQL> CREATE TABLE address LIKE customer_template.address; SQL> CREATE TABLE sales LIKE customer_template.sales; shell> maxctrl call command schemarouter invalidate Sharded-Service OK

Das Entfernen eines Mandanten von einem Shard ist hingegen etwas komplizierter und muss in Absprache mit der Applikation erfolgen:

SQL> DROP DATABASE customer_0011; shell> ./sharding_test.php .....ERROR: Table 'customer_0011.sales' doesn't exist...ERROR: Unknown database 'customer_0011'.ERROR: Unknown database 'customer_0011'......ERROR: Unknown database 'customer_0011'... shell> maxctrl call command schemarouter clear Sharded-Service OK

Zumindest ist mir bisher noch keine schlauere Variante eingefallen. Siehe auch Umziehen eines Mandanten weiter unten.

Umziehen eines Mandanten

Die Kombination von Hinzufügen und Entfernen wäre dann das Umziehen eines Mandanten von einem Shard auf ein anderes Shard, auch re-sharding genannt. Hierzu muss ebenfalls wieder mit der Applikation zusammen eine konzertierte Aktion geplant werden.

Falls dies nicht möglich ist, kann zumindest die Zeit, welche die Applikation Fehler erhält reduziert werden... Folgendes Vorgehen kann verwendet werden um einen Mandanten von Shard 2 auf Shard 3 umzuziehen:

SQL> use customer_0020; LOCK TABLES address READ, sales READ; -- Auf Shard 2, Applikation wir allenfalls blockiert! shell> mariadb-dump --user=app --password=secret --host=10.139.158.1 --port=3364 --single-transaction --skip-add-locks --databases customer_0020 | mariadb --user=app --password=secret --host=10.139.158.1 --port=3365 # Kopieren des Mandanten 20 von Shard 2 auf Shard 3 SQL> DROP DATABASE customer_0020; -- Löschen von Mandant 20 geht nicht! ERROR 1192 (HY000): Can't execute the given command because you have active locked tables or an active transaction SQL> UNLOCK TABLES; DROP DATABASE customer_0020; # So geht das Löschen von Mandant 20. shell> maxctrl call command schemarouter clear Sharded-Service # MaxScale Database Map aktualisieren. Schnell machen!!!
Bis zum Refresh der Database Map kann es zu folgenden Fehlern kommen: error : (47621) [schemarouter] (Sharded-Service); 'customer_0020.' found on servers 'shard2','shard3' for user 'app'@'10.139.158.1'. error : (47621) [schemarouter] (Sharded-Service); 'customer_0020.address' found on servers 'shard2','shard3' for user 'app'@'10.139.158.1'. error : (47621) [schemarouter] (Sharded-Service); 'customer_0020.sales' found on servers 'shard2','shard3' for user 'app'@'10.139.158.1'. error : (47621) [schemarouter] (Sharded-Service); Duplicate tables found, closing session.

Und applikationsseitig zu:

ERROR: Error: duplicate tables found on two different shards
Hinzufügen oder entfernen eines Shards

Das Umziehen eines Mandanten von einem Shard auf ein anderes Shard ist das kleine re-sharding. Etwas komplexer wird es, wenn man neue Shards hinzufügen oder alte Shards entfernen möchte. Im Anschluss daran (nach dem Hinzufügen bzw. vor dem Entfernen) würde dann ein grosses re-sharding erfolgen. Zuerst das Erweitern des Clusters um ein Shard:

shell> maxctrl list servers ┌────────┬──────────────┬──────┬─────────────┬─────────┬───────────────┬──────────────────┐ │ Server │ Address │ Port │ Connections │ State │ GTID │ Monitor │ ├────────┼──────────────┼──────┼─────────────┼─────────┼───────────────┼──────────────────┤ │ shard1 │ 10.139.158.1 │ 3363 │ 0 │ Running │ 0-3363-26014 │ Sharding-Monitor │ ├────────┼──────────────┼──────┼─────────────┼─────────┼───────────────┼──────────────────┤ │ shard2 │ 10.139.158.1 │ 3364 │ 0 │ Running │ 0-3364-240612 │ Sharding-Monitor │ ├────────┼──────────────┼──────┼─────────────┼─────────┼───────────────┼──────────────────┤ │ shard3 │ 10.139.158.1 │ 3365 │ 0 │ Running │ 0-3365-289873 │ Sharding-Monitor │ └────────┴──────────────┴──────┴─────────────┴─────────┴───────────────┴──────────────────┘

Das vorbereitete Shard wird MaxScale bekannt gemacht:

shell> maxctrl create server shard4 10.139.158.1 3366 OK shell> maxctrl list servers ┌────────┬──────────────┬──────┬─────────────┬─────────┬──────────────┬──────────────────┐ │ Server │ Address │ Port │ Connections │ State │ GTID │ Monitor │ ├────────┼──────────────┼──────┼─────────────┼─────────┼──────────────┼──────────────────┤ │ shard1 │ 10.139.158.1 │ 3363 │ 1 │ Running │ 0-3363-23676 │ Sharding-Monitor │ ├────────┼──────────────┼──────┼─────────────┼─────────┼──────────────┼──────────────────┤ │ shard2 │ 10.139.158.1 │ 3364 │ 1 │ Running │ 0-3364-52321 │ Sharding-Monitor │ ├────────┼──────────────┼──────┼─────────────┼─────────┼──────────────┼──────────────────┤ │ shard3 │ 10.139.158.1 │ 3365 │ 1 │ Running │ 0-3365-39751 │ Sharding-Monitor │ ├────────┼──────────────┼──────┼─────────────┼─────────┼──────────────┼──────────────────┤ │ shard4 │ 10.139.158.1 │ 3366 │ 0 │ Down │ │ │ └────────┴──────────────┴──────┴─────────────┴─────────┴──────────────┴──────────────────┘

Dann wird des neue Shard mit dem MaxScale Monitor und dem Service verknüpft:

shell> MAXCTRL_WARNINGS=0 maxctrl link monitor Sharding-Monitor shard4 OK shell> MAXCTRL_WARNINGS=0 maxctrl link service Sharded-Service shard4 OK shell> maxctrl list servers ┌────────┬──────────────┬──────┬─────────────┬─────────┬──────────────┬──────────────────┐ │ Server │ Address │ Port │ Connections │ State │ GTID │ Monitor │ ├────────┼──────────────┼──────┼─────────────┼─────────┼──────────────┼──────────────────┤ │ shard1 │ 10.139.158.1 │ 3363 │ 1 │ Running │ 0-3363-24961 │ Sharding-Monitor │ ├────────┼──────────────┼──────┼─────────────┼─────────┼──────────────┼──────────────────┤ │ shard2 │ 10.139.158.1 │ 3364 │ 1 │ Running │ 0-3364-56215 │ Sharding-Monitor │ ├────────┼──────────────┼──────┼─────────────┼─────────┼──────────────┼──────────────────┤ │ shard3 │ 10.139.158.1 │ 3365 │ 1 │ Running │ 0-3365-45177 │ Sharding-Monitor │ ├────────┼──────────────┼──────┼─────────────┼─────────┼──────────────┼──────────────────┤ │ shard4 │ 10.139.158.1 │ 3366 │ 1 │ Running │ 0-3366-32 │ Sharding-Monitor │ └────────┴──────────────┴──────┴─────────────┴─────────┴──────────────┴──────────────────┘

Ob dieser zweite Schritt ebenfalls zwingend notwendig ist, wurde nicht untersucht.

Im MariaDB MaxScale Error Log kann man den ganzen Ablauf mitverfolgen:

warning: Discarding journal file '/var/lib/maxscale/Sharding-Monitor_journal.json'. Servers described in the journal are different from the ones configured on the current monitor. warning: Saving runtime modifications to 'Sharding-Monitor' in '/var/lib/maxscale/maxscale.cnf.d/Sharding-Monitor.cnf'. The modified values will override the values found in the static configuration files. notice : shard4 sent version string '10.11.7-MariaDB-log'. Detected type: MariaDB, version: 10.11.7. notice : Server 'shard4' charset: latin1_swedish_ci notice : Server changed state: shard4[10.139.158.1:3366]: server_up. [Down] -> [Running] warning: Saving runtime modifications to 'Sharded-Service' in '/var/lib/maxscale/maxscale.cnf.d/Sharded-Service.cnf'. The modified values will override the values found in the static configuration files. notice : Added 'shard4' to 'Sharded-Service'

Was wir hier nicht vergessen dürfen, ist das neue Shard ebenfalls mit dem Proxy Protokoll auszustatten:

shell> maxctrl show server shard4 | grep proxy │ │ "proxy_protocol": false, │ MAXCTRL_WARNINGS=0 maxctrl alter server shard4 proxy_protocol=true OK

Und jetzt können neue Mandanten auf dem neuen Shard hinzugefügt oder alte Mandanten auf das neue Shard umgezogen werden... In unserem Set-up wollen wir alle Mandanten vom Shard 1 auf Shard 4 umziehen und zudem einen neuen Mandanten customer_0040 auf Shard 4 erstellen. Die dazu benötigten Einzelschritte sind oben aufgeführt.

Nachdem das Shard 1 leergeräumt wurde, kann es abgebaut werden:

shell> maxctrl list servers ┌────────┬──────────────┬──────┬─────────────┬─────────┬──────────────┬──────────────────┐ │ Server │ Address │ Port │ Connections │ State │ GTID │ Monitor │ ├────────┼──────────────┼──────┼─────────────┼─────────┼──────────────┼──────────────────┤ │ shard1 │ 10.139.158.1 │ 3363 │ 1 │ Running │ 0-3363-25916 │ Sharding-Monitor │ ├────────┼──────────────┼──────┼─────────────┼─────────┼──────────────┼──────────────────┤ │ shard2 │ 10.139.158.1 │ 3364 │ 1 │ Running │ 0-3364-62887 │ Sharding-Monitor │ ├────────┼──────────────┼──────┼─────────────┼─────────┼──────────────┼──────────────────┤ │ shard3 │ 10.139.158.1 │ 3365 │ 1 │ Running │ 0-3365-54035 │ Sharding-Monitor │ ├────────┼──────────────┼──────┼─────────────┼─────────┼──────────────┼──────────────────┤ │ shard4 │ 10.139.158.1 │ 3366 │ 1 │ Running │ 0-3366-2247 │ Sharding-Monitor │ └────────┴──────────────┴──────┴─────────────┴─────────┴──────────────┴──────────────────┘

Mit dem Befehl destroy server wir ein Shard gelöscht. Bevor das aber funktioniert muss ein Shard aus dem Monitor und dem Service entfernt werden:

shell> MAXCTRL_WARNINGS=0 maxctrl unlink service Sharded-Service shard1 OK shell> MAXCTRL_WARNINGS=0 maxctrl unlink monitor Sharding-Monitor shard1 OK shell> maxctrl list servers ┌────────┬──────────────┬──────┬─────────────┬─────────┬──────────────┬──────────────────┐ │ Server │ Address │ Port │ Connections │ State │ GTID │ Monitor │ ├────────┼──────────────┼──────┼─────────────┼─────────┼──────────────┼──────────────────┤ │ shard1 │ 10.139.158.1 │ 3363 │ 0 │ Running │ │ │ ├────────┼──────────────┼──────┼─────────────┼─────────┼──────────────┼──────────────────┤ │ shard2 │ 10.139.158.1 │ 3364 │ 1 │ Running │ 0-3364-64394 │ Sharding-Monitor │ ├────────┼──────────────┼──────┼─────────────┼─────────┼──────────────┼──────────────────┤ │ shard3 │ 10.139.158.1 │ 3365 │ 1 │ Running │ 0-3365-56072 │ Sharding-Monitor │ ├────────┼──────────────┼──────┼─────────────┼─────────┼──────────────┼──────────────────┤ │ shard4 │ 10.139.158.1 │ 3366 │ 1 │ Running │ 0-3366-3267 │ Sharding-Monitor │ └────────┴──────────────┴──────┴─────────────┴─────────┴──────────────┴──────────────────┘

Wenn das Shard aus dem Monitor und dem Service herausgelöst ist, kann es anschliessend gelöscht werden:

shell> maxctrl destroy server shard1 Warning: Object 'shard1' is defined in a static configuration file and cannot be permanently deleted. If MaxScale is restarted, the object will appear again. To hide these warnings, run: export MAXCTRL_WARNINGS=0 OK shell> maxctrl list servers ┌────────┬──────────────┬──────┬─────────────┬─────────┬──────────────┬──────────────────┐ │ Server │ Address │ Port │ Connections │ State │ GTID │ Monitor │ ├────────┼──────────────┼──────┼─────────────┼─────────┼──────────────┼──────────────────┤ │ shard2 │ 10.139.158.1 │ 3364 │ 1 │ Running │ 0-3364-65018 │ Sharding-Monitor │ ├────────┼──────────────┼──────┼─────────────┼─────────┼──────────────┼──────────────────┤ │ shard3 │ 10.139.158.1 │ 3365 │ 1 │ Running │ 0-3365-56886 │ Sharding-Monitor │ ├────────┼──────────────┼──────┼─────────────┼─────────┼──────────────┼──────────────────┤ │ shard4 │ 10.139.158.1 │ 3366 │ 1 │ Running │ 0-3366-3648 │ Sharding-Monitor │ └────────┴──────────────┴──────┴─────────────┴─────────┴──────────────┴──────────────────┘

Und im MaxScale Error Log kann man die Änderungen schön mitverfolgen:

notice : Removed 'shard1' from 'Sharded-Service' warning: Discarding journal file '/var/lib/maxscale/Sharding-Monitor_journal.json'. Servers described in the journal are different from the ones configured on the current monitor. notice : Destroyed server 'shard1' at 10.139.158.1:3363

Quelle:


Anpassen der Konfigurationsdateien

Bei den oben beschriebenen Shard Operationen habe wir einige Warnungen erhalten:

Warning: Object 'shard1' is defined in a static configuration file and cannot be permanently deleted. If MaxScale is restarted, the object will appear again.

und

Warning: Saving runtime modifications to 'Sharding-Monitor' in '/var/lib/maxscale/maxscale.cnf.d/Sharding-Monitor.cnf'. The modified values will override the values found in the static configuration files.

Die entsprechenden Konfigurationsdateien werden von MaxScale automatisch bei dynamischen System-Änderungen erstellt:

shell> ll /var/lib/maxscale/maxscale.cnf.d/ /etc/maxscale.cnf -rw-r--r-- 1 root root 612 Feb 13 14:23 /etc/maxscale.cnf /var/lib/maxscale/maxscale.cnf.d/: total 12 -rw------- 1 maxscale maxscale 187 Feb 13 16:08 Sharding-Monitor.cnf -rw------- 1 maxscale maxscale 150 Feb 13 16:07 Sharded-Service.cnf -rw------- 1 maxscale maxscale 52 Feb 13 15:46 shard4.cnf cat /var/lib/maxscale/maxscale.cnf.d/* [Sharded-Service] debug=true refresh_interval=10000ms auth_all_servers=true log_debug=true password=secret router=schemarouter type=service user=maxscale_admin targets=shard2,shard3,shard4 [Sharding-Monitor] module=galeramon monitor_interval=1000ms password=secret servers=shard2,shard3,shard4 type=monitor user=maxscale_monitor [shard4] address=10.139.158.1 port=3366 type=server

Es müssen also noch entsprechende Nachbesserungen an den Konfigurationsdateien vorgenommen werden. Man müsste sich allgemein überlegen ob man bei einem hochdynamischen System nicht alles dynamisch über Befehle konfigurieren sollte...

Wartungsarbeiten am Shard

Wenn für Wartungsarbeiten ein Shard offline genommen werden soll, hier im Beispiel shard2, kann dies wie folgt bewerkstelligt werden:

shell> maxctrl list servers ┌────────┬──────────────┬──────┬─────────────┬─────────┬──────────────┬──────────────────┐ │ Server │ Address │ Port │ Connections │ State │ GTID │ Monitor │ ├────────┼──────────────┼──────┼─────────────┼─────────┼──────────────┼──────────────────┤ │ shard2 │ 10.139.158.1 │ 3364 │ 1 │ Running │ 0-3364-69817 │ Sharding-Monitor │ ├────────┼──────────────┼──────┼─────────────┼─────────┼──────────────┼──────────────────┤ │ shard3 │ 10.139.158.1 │ 3365 │ 1 │ Running │ 0-3365-63166 │ Sharding-Monitor │ ├────────┼──────────────┼──────┼─────────────┼─────────┼──────────────┼──────────────────┤ │ shard4 │ 10.139.158.1 │ 3366 │ 1 │ Running │ 0-3366-6902 │ Sharding-Monitor │ └────────┴──────────────┴──────┴─────────────┴─────────┴──────────────┴──────────────────┘ shell> maxctrl set server shard2 drain OK shell> maxctrl set server shard2 maintenance OK shell> maxctrl list servers ┌────────┬──────────────┬──────┬─────────────┬──────────────────────┬───────────────┬──────────────────┐ │ Server │ Address │ Port │ Connections │ State │ GTID │ Monitor │ ├────────┼──────────────┼──────┼─────────────┼──────────────────────┼───────────────┼──────────────────┤ │ shard2 │ 10.139.158.1 │ 3364 │ 0 │ Maintenance, Running │ 0-3364-240612 │ Sharding-Monitor │ ├────────┼──────────────┼──────┼─────────────┼──────────────────────┼───────────────┼──────────────────┤ │ shard3 │ 10.139.158.1 │ 3365 │ 0 │ Running │ 0-3365-289873 │ Sharding-Monitor │ ├────────┼──────────────┼──────┼─────────────┼──────────────────────┼───────────────┼──────────────────┤ │ shard4 │ 10.139.158.1 │ 3366 │ 0 │ Running │ 0-3366-119848 │ Sharding-Monitor │ └────────┴──────────────┴──────┴─────────────┴──────────────────────┴───────────────┴──────────────────┘

Zu diesem Zeitpunkt können die Wartungsarbeiten an der Maschine oder der Datenbank vorgenommen werden...

Anschliessend müssen BEIDE Stati wieder gecleared werden, sofern bei gesetzt wurden:

shell> maxctrl clear server shard2 maintenance OK shell> maxctrl clear server shard2 drain OK maxctrl list servers ┌────────┬──────────────┬──────┬─────────────┬─────────┬───────────────┬──────────────────┐ │ Server │ Address │ Port │ Connections │ State │ GTID │ Monitor │ ├────────┼──────────────┼──────┼─────────────┼─────────┼───────────────┼──────────────────┤ │ shard2 │ 10.139.158.1 │ 3364 │ 0 │ Running │ 0-3364-240612 │ Sharding-Monitor │ ├────────┼──────────────┼──────┼─────────────┼─────────┼───────────────┼──────────────────┤ │ shard3 │ 10.139.158.1 │ 3365 │ 0 │ Running │ 0-3365-289873 │ Sharding-Monitor │ ├────────┼──────────────┼──────┼─────────────┼─────────┼───────────────┼──────────────────┤ │ shard4 │ 10.139.158.1 │ 3366 │ 0 │ Running │ 0-3366-119848 │ Sharding-Monitor │ └────────┴──────────────┴──────┴─────────────┴─────────┴───────────────┴──────────────────┘

Der Unterschied zwischen drain und maintenance besteht darin, dass bei drain keinen neuen Verbindungen mehr auf das Shard zugelassen werden aber bei bestehenden Verbindungen wird gewartet, bis sie geschlossen werden. Bei maintenance werden die Verbindungen sofort zwangsweise terminiert.

Beobachtung / Observierung eines MariaDB MaxScale Sharding-Systems

Mit dem MaxScale CLI Client maxtrl kann man den Zustand des MariaDB MaxScale Load Balancers abfragen hierzu gibt es zahlreiche Befehle, hauptsächlich list und show:

shell> maxctrl show module schemarouter | head -n 12 ┌─────────────┬────────────────────────────────────────────────┐ │ Module │ schemarouter │ ├─────────────┼────────────────────────────────────────────────┤ │ Type │ Router │ ├─────────────┼────────────────────────────────────────────────┤ │ Version │ V1.0.0 │ ├─────────────┼────────────────────────────────────────────────┤ │ Maturity │ Beta │ ├─────────────┼────────────────────────────────────────────────┤ │ Description │ A database sharding router for simple sharding │ ├─────────────┼────────────────────────────────────────────────┤ │ Parameters │ ... │ shell> maxctrl list servers ┌────────┬──────────────┬──────┬─────────────┬─────────┬───────────────┬──────────────────┐ │ Server │ Address │ Port │ Connections │ State │ GTID │ Monitor │ ├────────┼──────────────┼──────┼─────────────┼─────────┼───────────────┼──────────────────┤ │ shard2 │ 10.139.158.1 │ 3364 │ 4 │ Running │ 0-3364-290859 │ Sharding-Monitor │ ├────────┼──────────────┼──────┼─────────────┼─────────┼───────────────┼──────────────────┤ │ shard3 │ 10.139.158.1 │ 3365 │ 4 │ Running │ 0-3365-322671 │ Sharding-Monitor │ ├────────┼──────────────┼──────┼─────────────┼─────────┼───────────────┼──────────────────┤ │ shard4 │ 10.139.158.1 │ 3366 │ 4 │ Running │ 0-3366-140018 │ Sharding-Monitor │ └────────┴──────────────┴──────┴─────────────┴─────────┴───────────────┴──────────────────┘

Die Information für die Spalte Connections ist verwirrend, da wir bei diesem Sharding-System in diesem Fall auf jedem Shard nur 1, 1 und 2 Verbindungen offen haben.

Wenn man sich mit SHOW PROCESSLIST die Situation aber auf dem jeweiligen Shard anschaut, sieht man, dass MaxScale auf JEDEM Shard für jede eingehende Verbindung auch eine Verbindung auf jedes Shard aufbaut. Somit ist die Anzeige oben eigentlich technisch korrekt, nur nicht, was man erwarten würde:

SQL> SHOW PROCESSLIST; +--------+------------------+----------------------+---------------+---------+------+----------+-----------------------------------------------------------------+----------+ | Id | User | Host | db | Command | Time | State | Info | Progress | +--------+------------------+----------------------+---------------+---------+------+----------+-----------------------------------------------------------------+----------+ | 123 | root | localhost | customer_0021 | Query | 0 | starting | show processlist | 0.000 | | 68107 | maxscale_monitor | 10.139.158.211:35418 | NULL | Sleep | 0 | | NULL | 0.000 | | 113372 | app | 10.139.158.1:47548 | NULL | Sleep | 47 | | NULL | 0.000 | | 113538 | app | 10.139.158.1:49058 | NULL | Sleep | 41 | | NULL | 0.000 | | 113662 | app | 10.139.158.1:47072 | NULL | Sleep | 37 | | NULL | 0.000 | | 114789 | app | 10.139.158.1:39574 | customer_0022 | Query | 0 | Updating | UPDATE sales SET product = 'Prepare to delete' WHERE id = 15622 | 0.000 | +--------+------------------+----------------------+---------------+---------+------+----------+-----------------------------------------------------------------+----------+

Das skaliert so nicht bei grossen Systemen mit hunderten oder tausenden von Mandanten! Ev. kommt in diesem Fall das MariaDB Thread Pool Feature zum Einsatz.

Laut dem MaxScale Entwickler ist dies gewünschtes/beabsichtigtes Verhalten...

shell> maxctrl list services ┌─────────────────┬──────────────┬─────────────┬───────────────────┬────────────────────────┐ │ Service │ Router │ Connections │ Total Connections │ Targets │ ├─────────────────┼──────────────┼─────────────┼───────────────────┼────────────────────────┤ │ Sharded-Service │ schemarouter │ 4 │ 82776 │ shard2, shard3, shard4 │ └─────────────────┴──────────────┴─────────────┴───────────────────┴────────────────────────┘ shell> maxctrl list listeners ┌──────────────────────────┬──────┬──────┬─────────┬─────────────────┐ │ Name │ Port │ Host │ State │ Service │ ├──────────────────────────┼──────┼──────┼─────────┼─────────────────┤ │ Sharded-Service-Listener │ 3306 │ :: │ Running │ Sharded-Service │ └──────────────────────────┴──────┴──────┴─────────┴─────────────────┘ shell> maxctrl list monitors ┌──────────────────┬─────────┬────────────────────────┐ │ Monitor │ State │ Servers │ ├──────────────────┼─────────┼────────────────────────┤ │ Sharding-Monitor │ Running │ shard2, shard3, shard4 │ └──────────────────┴─────────┴────────────────────────┘ shell> maxctrl show server shard2 | head -n 20 ┌─────────────────────┬──────────────────────────────────────────────┐ │ Server │ shard2 │ ├─────────────────────┼──────────────────────────────────────────────┤ │ Source │ /etc/maxscale.cnf │ ├─────────────────────┼──────────────────────────────────────────────┤ │ Address │ 10.139.158.1 │ ├─────────────────────┼──────────────────────────────────────────────┤ │ Port │ 3364 │ ├─────────────────────┼──────────────────────────────────────────────┤ │ State │ Running │ ├─────────────────────┼──────────────────────────────────────────────┤ │ Version │ 10.11.7-MariaDB-log │ ├─────────────────────┼──────────────────────────────────────────────┤ │ Uptime │ 178960 │ ├─────────────────────┼──────────────────────────────────────────────┤ │ Last Event │ server_down │ ├─────────────────────┼──────────────────────────────────────────────┤ │ Triggered At │ Sun, 04 Feb 2024 07:37:17 GMT │ ├─────────────────────┼──────────────────────────────────────────────┤ │ Services │ Sharded-Service │ ├─────────────────────┼──────────────────────────────────────────────┤ │ Monitors │ Sharding-Monitor │ ├─────────────────────┼──────────────────────────────────────────────┤ ... ├─────────────────────┼──────────────────────────────────────────────┤ │ Current Connections │ 5 │ ├─────────────────────┼──────────────────────────────────────────────┤ │ Total Connections │ 27 │ ├─────────────────────┼──────────────────────────────────────────────┤ │ Max Connections │ 5 │ shell> maxctrl show service Sharded-Service ┌─────────────────────┬──────────────────────────────────────────────────────┐ │ Service │ Sharded-Service │ ├─────────────────────┼──────────────────────────────────────────────────────┤ │ Source │ /var/lib/maxscale/maxscale.cnf.d/Sharded-Service.cnf │ ├─────────────────────┼──────────────────────────────────────────────────────┤ │ Router │ schemarouter │ ├─────────────────────┼──────────────────────────────────────────────────────┤ │ State │ Started │ ├─────────────────────┼──────────────────────────────────────────────────────┤ │ Started At │ 3/18/2024, 1:52:30 PM │ ├─────────────────────┼──────────────────────────────────────────────────────┤ │ Users Loaded At │ 3/18/2024, 1:52:30 PM │ ├─────────────────────┼──────────────────────────────────────────────────────┤ │ Current Connections │ 4 │ ├─────────────────────┼──────────────────────────────────────────────────────┤ │ Total Connections │ 84590 │ ├─────────────────────┼──────────────────────────────────────────────────────┤ │ Max Connections │ 5 │ ├─────────────────────┼──────────────────────────────────────────────────────┤ │ Cluster │ │ ├─────────────────────┼──────────────────────────────────────────────────────┤ │ Servers │ shard2 │ │ │ shard3 │ │ │ shard4 │ ├─────────────────────┼──────────────────────────────────────────────────────┤ │ Services │ │ ├─────────────────────┼──────────────────────────────────────────────────────┤ │ Filters │ │ ├─────────────────────┼──────────────────────────────────────────────────────┤ │ Parameters │ { │ │ │ "auth_all_servers": true, │ │ │ "connection_keepalive": "300000ms", │ │ │ "debug": true, │ │ │ "disable_sescmd_history": false, │ │ │ "enable_root_user": false, │ │ │ "force_connection_keepalive": false, │ │ │ "idle_session_pool_time": "-1ms", │ │ │ "ignore_tables": [], │ │ │ "ignore_tables_regex": null, │ │ │ "localhost_match_wildcard_host": true, │ │ │ "log_auth_warnings": true, │ │ │ "log_debug": true, │ │ │ "log_info": false, │ │ │ "log_notice": false, │ │ │ "log_warning": false, │ │ │ "max_connections": 0, │ │ │ "max_sescmd_history": 50, │ │ │ "max_staleness": "150000ms", │ │ │ "multiplex_timeout": "60000ms", │ │ │ "net_write_timeout": "0ms", │ │ │ "password": "*****", │ │ │ "prune_sescmd_history": true, │ │ │ "rank": "primary", │ │ │ "refresh_databases": false, │ │ │ "refresh_interval": "10000ms", │ │ │ "retain_last_statements": -1, │ │ │ "router": "schemarouter", │ │ │ "session_trace": false, │ │ │ "strip_db_esc": true, │ │ │ "type": "service", │ │ │ "user": "maxscale_admin", │ │ │ "user_accounts_file": null, │ │ │ "user_accounts_file_usage": "add_when_load_ok", │ │ │ "version_string": null, │ │ │ "wait_timeout": "0ms" │ │ │ } │ ├─────────────────────┼──────────────────────────────────────────────────────┤ │ Router Diagnostics │ { │ │ │ "average_session": 0.028822357131634554, │ │ │ "longest_sescmd_chain": 4, │ │ │ "longest_session": 50, │ │ │ "queries": 761134, │ │ │ "sescmd_percentage": 44.44342257736483, │ │ │ "shard_map_hits": 84356, │ │ │ "shard_map_misses": 5, │ │ │ "shard_map_stale": 229, │ │ │ "shard_map_updates": 216, │ │ │ "shortest_session": 0, │ │ │ "times_sescmd_limit_exceeded": 0 │ │ │ } │ └─────────────────────┴──────────────────────────────────────────────────────┘

Siehe hierzu auch MaxScale SchemaRouter Router diagnostics.

shell> maxctrl show monitor Sharding-Monitor ┌─────────────────────┬──────────────────────────────────────────────────────────┐ │ Monitor │ Sharding-Monitor │ ├─────────────────────┼──────────────────────────────────────────────────────────┤ │ Source │ /etc/maxscale.cnf │ ├─────────────────────┼──────────────────────────────────────────────────────────┤ │ Module │ galeramon │ ├─────────────────────┼──────────────────────────────────────────────────────────┤ │ State │ Running │ ├─────────────────────┼──────────────────────────────────────────────────────────┤ │ Servers │ shard1 │ │ │ shard2 │ │ │ shard3 │ ├─────────────────────┼──────────────────────────────────────────────────────────┤ │ Parameters │ { │ │ │ "available_when_donor": false, │ │ │ "backend_connect_attempts": 1, │ │ │ "backend_connect_timeout": "3000ms", │ │ │ "backend_read_timeout": "3000ms", │ │ │ "backend_write_timeout": "3000ms", │ │ │ "disable_master_failback": false, │ │ │ "disable_master_role_setting": false, │ │ │ "disk_space_check_interval": "0ms", │ │ │ "disk_space_threshold": null, │ │ │ "events": "all,master_down,master_up,...,new_donor", │ │ │ "journal_max_age": "28800000ms", │ │ │ "module": "galeramon", │ │ │ "monitor_interval": "1000ms", │ │ │ "password": "*****", │ │ │ "root_node_as_master": false, │ │ │ "script": null, │ │ │ "script_timeout": "90000ms", │ │ │ "set_donor_nodes": false, │ │ │ "type": "monitor", │ │ │ "use_priority": false, │ │ │ "user": "maxscale_monitor" │ │ │ } │ ├─────────────────────┼──────────────────────────────────────────────────────────┤ │ Monitor Diagnostics │ { │ │ │ "disable_master_failback": false, │ │ │ "disable_master_role_setting": false, │ │ │ "root_node_as_master": false, │ │ │ "server_info": [ │ │ │ { │ │ │ "gtid_binlog_pos": "0-3363-26014", │ │ │ "gtid_current_pos": "0-3363-26014", │ │ │ "master_id": 0, │ │ │ "name": "shard1", │ │ │ "read_only": false, │ │ │ "server_id": 3363 │ │ │ }, │ │ │ { │ │ │ "gtid_binlog_pos": "0-3364-240612", │ │ │ "gtid_current_pos": "0-3364-240612", │ │ │ "master_id": 0, │ │ │ "name": "shard2", │ │ │ "read_only": false, │ │ │ "server_id": 3364 │ │ │ }, │ │ │ { │ │ │ "gtid_binlog_pos": "0-3365-289873", │ │ │ "gtid_current_pos": "0-3365-289873", │ │ │ "master_id": 0, │ │ │ "name": "shard3", │ │ │ "read_only": false, │ │ │ "server_id": 3365 │ │ │ } │ │ │ ], │ │ │ "set_donor_nodes": false, │ │ │ "use_priority": false │ │ │ } │ └─────────────────────┴──────────────────────────────────────────────────────────┘ shell> maxctrl list sessions; ┌───────┬──────┬──────────────┬───────────────────────┬───────┬─────────────────┬────────┬──────────────┐ │ Id │ User │ Host │ Connected │ Idle │ Service │ Memory │ I/O-Activity │ ├───────┼──────┼──────────────┼───────────────────────┼───────┼─────────────────┼────────┼──────────────┤ │ 87240 │ app │ 10.139.158.1 │ 3/18/2024, 2:33:54 PM │ 0 │ Sharded-Service │ 68644 │ 33 │ ├───────┼──────┼──────────────┼───────────────────────┼───────┼─────────────────┼────────┼──────────────┤ │ 72654 │ app │ 10.139.158.1 │ 3/18/2024, 2:25:27 PM │ 506.3 │ Sharded-Service │ 199328 │ 0 │ ├───────┼──────┼──────────────┼───────────────────────┼───────┼─────────────────┼────────┼──────────────┤ │ 72364 │ app │ 10.139.158.1 │ 3/18/2024, 2:25:18 PM │ 516 │ Sharded-Service │ 199328 │ 0 │ ├───────┼──────┼──────────────┼───────────────────────┼───────┼─────────────────┼────────┼──────────────┤ │ 72530 │ app │ 10.139.158.1 │ 3/18/2024, 2:25:23 PM │ 510.5 │ Sharded-Service │ 199328 │ 0 │ └───────┴──────┴──────────────┴───────────────────────┴───────┴─────────────────┴────────┴──────────────┘ shell> maxctrl show session 26 ┌───────────────────────┬───────────────────────────────────────┐ │ Id │ 26 │ ├───────────────────────┼───────────────────────────────────────┤ │ Service │ Sharded-Service │ ├───────────────────────┼───────────────────────────────────────┤ │ State │ Session started │ ├───────────────────────┼───────────────────────────────────────┤ │ User │ app │ ├───────────────────────┼───────────────────────────────────────┤ │ Host │ 10.139.158.1 │ ├───────────────────────┼───────────────────────────────────────┤ │ Port │ 42854 │ ├───────────────────────┼───────────────────────────────────────┤ │ Database │ │ ├───────────────────────┼───────────────────────────────────────┤ │ Connected │ 2/4/2024, 9:31:12 AM │ ├───────────────────────┼───────────────────────────────────────┤ │ Idle │ 610.4 │ ├───────────────────────┼───────────────────────────────────────┤ │ Parameters │ { │ │ │ "log_error": false, │ │ │ "log_info": false, │ │ │ "log_notice": false, │ │ │ "log_warning": false │ │ │ } │ ├───────────────────────┼───────────────────────────────────────┤ │ Client TLS Cipher │ │ ├───────────────────────┼───────────────────────────────────────┤ │ Connection attributes │ { │ │ │ "_client_name": "libmariadb", │ │ │ "_client_version": "3.3.8", │ │ │ "_os": "Linux", │ │ │ "_pid": "251037", │ │ │ "_platform": "x86_64", │ │ │ "_server_host": "10.139.158.211", │ │ │ "program_name": "mysql" │ │ │ } │ ├───────────────────────┼───────────────────────────────────────┤ │ Connections │ shard1 │ │ │ shard2 │ │ │ shard3 │ ├───────────────────────┼───────────────────────────────────────┤ │ Connection IDs │ 666 │ │ │ 139 │ │ │ 138 │ ├───────────────────────┼───────────────────────────────────────┤ │ Queries │ │ ├───────────────────────┼───────────────────────────────────────┤ │ Log │ │ ├───────────────────────┼───────────────────────────────────────┤ │ Memory │ { │ │ │ "connection_buffers": { │ │ │ "backends": { │ │ │ "shard1": { │ │ │ "misc": 678, │ │ │ "readq": 65536, │ │ │ "total": 66214, │ │ │ "writeq": 0 │ │ │ }, │ │ │ "shard2": { │ │ │ "misc": 662, │ │ │ "readq": 0, │ │ │ "total": 662, │ │ │ "writeq": 0 │ │ │ }, │ │ │ "shard3": { │ │ │ "misc": 678, │ │ │ "readq": 65536, │ │ │ "total": 66214, │ │ │ "writeq": 0 │ │ │ } │ │ │ }, │ │ │ "client": { │ │ │ "misc": 654, │ │ │ "readq": 65536, │ │ │ "total": 66190, │ │ │ "writeq": 0 │ │ │ }, │ │ │ "total": 199280 │ │ │ }, │ │ │ "exec_metadata": 0, │ │ │ "last_queries": 0, │ │ │ "sescmd_history": 48, │ │ │ "total": 199328, │ │ │ "variables": 0 │ │ │ } │ ├───────────────────────┼───────────────────────────────────────┤ │ I/O Activity │ 0 │ └───────────────────────┴───────────────────────────────────────┘ shell> maxctrl show listener Sharded-Service-Listener ┌────────────┬───────────────────────────────────────────┐ │ Name │ Sharded-Service-Listener │ ├────────────┼───────────────────────────────────────────┤ │ Source │ /etc/maxscale.cnf │ ├────────────┼───────────────────────────────────────────┤ │ Service │ Sharded-Service │ ├────────────┼───────────────────────────────────────────┤ │ Parameters │ { │ │ │ "MariaDBProtocol": { │ │ │ "allow_replication": true │ │ │ }, │ │ │ "address": "::", │ │ │ "authenticator": null, │ │ │ "authenticator_options": null, │ │ │ "connection_init_sql_file": null, │ │ │ "connection_metadata": [ │ │ │ "character_set_client=auto", │ │ │ "character_set_connection=auto", │ │ │ "character_set_results=auto", │ │ │ "max_allowed_packet=auto", │ │ │ "system_time_zone=auto", │ │ │ "time_zone=auto", │ │ │ "tx_isolation=auto" │ │ │ ], │ │ │ "port": 3306, │ │ │ "protocol": "MariaDBProtocol", │ │ │ "proxy_protocol_networks": null, │ │ │ "service": "Sharded-Service", │ │ │ "socket": null, │ │ │ "sql_mode": "default", │ │ │ "ssl": false, │ │ │ "ssl_ca": null, │ │ │ "ssl_cert": null, │ │ │ "ssl_cert_verify_depth": 9, │ │ │ "ssl_cipher": null, │ │ │ "ssl_crl": null, │ │ │ "ssl_key": null, │ │ │ "ssl_verify_peer_certificate": false, │ │ │ "ssl_verify_peer_host": false, │ │ │ "ssl_version": "MAX", │ │ │ "type": "listener", │ │ │ "user_mapping_file": null │ │ │ } │ └────────────┴───────────────────────────────────────────┘ shell> maxctrl show module schemarouter ┌─────────────┬─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┐ │ Module │ schemarouter │ ├─────────────┼─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┤ │ Type │ Router │ ├─────────────┼─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┤ │ Version │ V1.0.0 │ ├─────────────┼─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┤ │ Maturity │ Beta │ ├─────────────┼─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┤ │ Description │ A database sharding router for simple sharding │ ├─────────────┼─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┤ │ Parameters │ [ │ │ │ { │ │ │ "default_value": false, │ │ │ "description": "Enable debug mode", │ │ │ "mandatory": false, │ │ │ "modifiable": true, │ │ │ "name": "debug", │ │ │ "type": "bool" │ │ │ }, │ │ │ { │ │ │ "default_value": [], │ │ │ "description": "List of tables to ignore when checking for duplicates", │ │ │ "mandatory": false, │ │ │ "modifiable": true, │ │ │ "name": "ignore_tables", │ │ │ "type": "stringlist" │ │ │ }, │ │ │ { │ │ │ "description": "Regex of tables to ignore when checking for duplicates", │ │ │ "mandatory": false, │ │ │ "modifiable": true, │ │ │ "name": "ignore_tables_regex", │ │ │ "type": "regex" │ │ │ }, │ │ │ { │ │ │ "default_value": "150000ms", │ │ │ "description": "Maximum allowed staleness of a database map entry before clients block and wait for an update", │ │ │ "mandatory": false, │ │ │ "modifiable": true, │ │ │ "name": "max_staleness", │ │ │ "type": "duration", │ │ │ "unit": "ms" │ │ │ }, │ │ │ { │ │ │ "default_value": false, │ │ │ "description": "Refresh database mapping information", │ │ │ "mandatory": false, │ │ │ "modifiable": true, │ │ │ "name": "refresh_databases", │ │ │ "type": "bool" │ │ │ }, │ │ │ { │ │ │ "default_value": "300000ms", │ │ │ "description": "How often to refresh the database mapping information", │ │ │ "mandatory": false, │ │ │ "modifiable": true, │ │ │ "name": "refresh_interval", │ │ │ "type": "duration", │ │ │ "unit": "ms" │ │ │ }, │ │ │ { │ │ │ "default_value": false, │ │ │ "description": "Retrieve users from all backend servers instead of only one", │ │ │ "mandatory": false, │ │ │ "modifiable": true, │ │ │ "name": "auth_all_servers", │ │ │ "type": "bool" │ │ │ }, │ │ │ { │ │ │ "default_value": "300000ms", │ │ │ "description": "How ofted idle connections are pinged", │ │ │ "mandatory": false, │ │ │ "modifiable": true, │ │ │ "name": "connection_keepalive", │ │ │ "type": "duration", │ │ │ "unit": "ms" │ │ │ }, │ │ │ { │ │ │ "deprecated": true, │ │ │ "description": "Alias for 'wait_timeout'", │ │ │ "mandatory": false, │ │ │ "modifiable": true, │ │ │ "name": "connection_timeout", │ │ │ "type": "duration" │ │ │ }, │ │ │ { │ │ │ "default_value": false, │ │ │ "description": "Disable session command history", │ │ │ "mandatory": false, │ │ │ "modifiable": true, │ │ │ "name": "disable_sescmd_history", │ │ │ "type": "bool" │ │ │ }, │ │ │ { │ │ │ "default_value": false, │ │ │ "description": "Allow the root user to connect to this service", │ │ │ "mandatory": false, │ │ │ "modifiable": true, │ │ │ "name": "enable_root_user", │ │ │ "type": "bool" │ │ │ }, │ │ │ { │ │ │ "default_value": false, │ │ │ "description": "Ping connections unconditionally", │ │ │ "mandatory": false, │ │ │ "modifiable": true, │ │ │ "name": "force_connection_keepalive", │ │ │ "type": "bool" │ │ │ }, │ │ │ { │ │ │ "default_value": "-1ms", │ │ │ "description": "Put connections into pool after session has been idle for this long", │ │ │ "mandatory": false, │ │ │ "modifiable": true, │ │ │ "name": "idle_session_pool_time", │ │ │ "type": "duration", │ │ │ "unit": "ms" │ │ │ }, │ │ │ { │ │ │ "default_value": true, │ │ │ "description": "Match localhost to wildcard host", │ │ │ "mandatory": false, │ │ │ "modifiable": true, │ │ │ "name": "localhost_match_wildcard_host", │ │ │ "type": "bool" │ │ │ }, │ │ │ { │ │ │ "default_value": true, │ │ │ "description": "Log a warning when client authentication fails", │ │ │ "mandatory": false, │ │ │ "modifiable": true, │ │ │ "name": "log_auth_warnings", │ │ │ "type": "bool" │ │ │ }, │ │ │ { │ │ │ "default_value": false, │ │ │ "description": "Log debug messages for this service (debug builds only)", │ │ │ "mandatory": false, │ │ │ "modifiable": true, │ │ │ "name": "log_debug", │ │ │ "type": "bool" │ │ │ }, │ │ │ { │ │ │ "default_value": false, │ │ │ "description": "Log info messages for this service", │ │ │ "mandatory": false, │ │ │ "modifiable": true, │ │ │ "name": "log_info", │ │ │ "type": "bool" │ │ │ }, │ │ │ { │ │ │ "default_value": false, │ │ │ "description": "Log notice messages for this service", │ │ │ "mandatory": false, │ │ │ "modifiable": true, │ │ │ "name": "log_notice", │ │ │ "type": "bool" │ │ │ }, │ │ │ { │ │ │ "default_value": false, │ │ │ "description": "Log warning messages for this service", │ │ │ "mandatory": false, │ │ │ "modifiable": true, │ │ │ "name": "log_warning", │ │ │ "type": "bool" │ │ │ }, │ │ │ { │ │ │ "default_value": 0, │ │ │ "description": "Maximum number of connections", │ │ │ "mandatory": false, │ │ │ "modifiable": true, │ │ │ "name": "max_connections", │ │ │ "type": "count" │ │ │ }, │ │ │ { │ │ │ "default_value": 50, │ │ │ "description": "Session command history size", │ │ │ "mandatory": false, │ │ │ "modifiable": true, │ │ │ "name": "max_sescmd_history", │ │ │ "type": "count" │ │ │ }, │ │ │ { │ │ │ "default_value": "60000ms", │ │ │ "description": "How long a session can wait for a connection to become available", │ │ │ "mandatory": false, │ │ │ "modifiable": true, │ │ │ "name": "multiplex_timeout", │ │ │ "type": "duration", │ │ │ "unit": "ms" │ │ │ }, │ │ │ { │ │ │ "default_value": "0ms", │ │ │ "description": "Network write timeout", │ │ │ "mandatory": false, │ │ │ "modifiable": true, │ │ │ "name": "net_write_timeout", │ │ │ "type": "duration", │ │ │ "unit": "ms" │ │ │ }, │ │ │ { │ │ │ "description": "Password for the user used to retrieve database users", │ │ │ "mandatory": true, │ │ │ "modifiable": true, │ │ │ "name": "password", │ │ │ "type": "password" │ │ │ }, │ │ │ { │ │ │ "default_value": true, │ │ │ "description": "Prune old session command history if the limit is exceeded", │ │ │ "mandatory": false, │ │ │ "modifiable": true, │ │ │ "name": "prune_sescmd_history", │ │ │ "type": "bool" │ │ │ }, │ │ │ { │ │ │ "default_value": "primary", │ │ │ "description": "Service rank", │ │ │ "enum_values": [ │ │ │ "primary", │ │ │ "secondary" │ │ │ ], │ │ │ "mandatory": false, │ │ │ "modifiable": true, │ │ │ "name": "rank", │ │ │ "type": "enum" │ │ │ }, │ │ │ { │ │ │ "default_value": -1, │ │ │ "description": "Number of statements kept in memory", │ │ │ "mandatory": false, │ │ │ "modifiable": true, │ │ │ "name": "retain_last_statements", │ │ │ "type": "int" │ │ │ }, │ │ │ { │ │ │ "default_value": false, │ │ │ "description": "Enable session tracing for this service", │ │ │ "mandatory": false, │ │ │ "modifiable": true, │ │ │ "name": "session_trace", │ │ │ "type": "bool" │ │ │ }, │ │ │ { │ │ │ "default_value": false, │ │ │ "deprecated": true, │ │ │ "description": "Track session state using server responses", │ │ │ "mandatory": false, │ │ │ "modifiable": true, │ │ │ "name": "session_track_trx_state", │ │ │ "type": "bool" │ │ │ }, │ │ │ { │ │ │ "default_value": true, │ │ │ "deprecated": true, │ │ │ "description": "Strip escape characters from database names", │ │ │ "mandatory": false, │ │ │ "modifiable": true, │ │ │ "name": "strip_db_esc", │ │ │ "type": "bool" │ │ │ }, │ │ │ { │ │ │ "description": "Username used to retrieve database users", │ │ │ "mandatory": true, │ │ │ "modifiable": true, │ │ │ "name": "user", │ │ │ "type": "string" │ │ │ }, │ │ │ { │ │ │ "description": "Load additional users from a file", │ │ │ "mandatory": false, │ │ │ "modifiable": false, │ │ │ "name": "user_accounts_file", │ │ │ "type": "path" │ │ │ }, │ │ │ { │ │ │ "default_value": "add_when_load_ok", │ │ │ "description": "When and how the user accounts file is used", │ │ │ "enum_values": [ │ │ │ "add_when_load_ok", │ │ │ "file_only_always" │ │ │ ], │ │ │ "mandatory": false, │ │ │ "modifiable": false, │ │ │ "name": "user_accounts_file_usage", │ │ │ "type": "enum" │ │ │ }, │ │ │ { │ │ │ "description": "Custom version string to use", │ │ │ "mandatory": false, │ │ │ "modifiable": true, │ │ │ "name": "version_string", │ │ │ "type": "string" │ │ │ }, │ │ │ { │ │ │ "default_value": "0ms", │ │ │ "description": "Connection idle timeout", │ │ │ "mandatory": false, │ │ │ "modifiable": true, │ │ │ "name": "wait_timeout", │ │ │ "type": "duration", │ │ │ "unit": "ms" │ │ │ } │ │ │ ] │ ├─────────────┼─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┤ │ Commands │ [ │ │ │ { │ │ │ "attributes": { │ │ │ "arg_max": 1, │ │ │ "arg_min": 1, │ │ │ "description": "Clear schemarouter shard map cache", │ │ │ "method": "POST", │ │ │ "parameters": [ │ │ │ { │ │ │ "description": "The schemarouter service", │ │ │ "required": true, │ │ │ "type": "SERVICE" │ │ │ } │ │ │ ] │ │ │ }, │ │ │ "id": "clear", │ │ │ "links": { │ │ │ "self": "http://127.0.0.1:8989/v1/modules/schemarouter/clear/" │ │ │ }, │ │ │ "type": "module_command" │ │ │ }, │ │ │ { │ │ │ "attributes": { │ │ │ "arg_max": 1, │ │ │ "arg_min": 1, │ │ │ "description": "Invalidate schemarouter shard map cache", │ │ │ "method": "POST", │ │ │ "parameters": [ │ │ │ { │ │ │ "description": "The schemarouter service", │ │ │ "required": true, │ │ │ "type": "SERVICE" │ │ │ } │ │ │ ] │ │ │ }, │ │ │ "id": "invalidate", │ │ │ "links": { │ │ │ "self": "http://127.0.0.1:8989/v1/modules/schemarouter/invalidate/" │ │ │ }, │ │ │ "type": "module_command" │ │ │ } │ │ │ ] │ └─────────────┴─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┘ shell> maxctrl show commands schemarouter ┌────────────┬────────────┬──────────────────────────┐ │ Command │ Parameters │ Descriptions │ ├────────────┼────────────┼──────────────────────────┤ │ clear │ SERVICE │ The schemarouter service │ ├────────────┼────────────┼──────────────────────────┤ │ invalidate │ SERVICE │ The schemarouter service │ └────────────┴────────────┴──────────────────────────┘ shell> maxctrl show dbusers Sharded-Service ┌───────────────────────┬────────────────┬───────────────────────┬───────┬───────┬────────┬───────┬──────┐ │ User │ Host │ Plugin │ TLS │ Super │ Global │ Proxy │ Role │ ├───────────────────────┼────────────────┼───────────────────────┼───────┼───────┼────────┼───────┼──────┤ │ PUBLIC │ │ │ false │ false │ false │ false │ │ ├───────────────────────┼────────────────┼───────────────────────┼───────┼───────┼────────┼───────┼──────┤ │ app │ 10.139.158.% │ mysql_native_password │ false │ false │ false │ false │ │ ├───────────────────────┼────────────────┼───────────────────────┼───────┼───────┼────────┼───────┼──────┤ │ app_role │ │ │ false │ false │ false │ false │ │ ├───────────────────────┼────────────────┼───────────────────────┼───────┼───────┼────────┼───────┼──────┤ │ mariadb.sys │ localhost │ mysql_native_password │ false │ false │ false │ false │ │ ├───────────────────────┼────────────────┼───────────────────────┼───────┼───────┼────────┼───────┼──────┤ │ maxscale_admin │ 10.139.158.210 │ mysql_native_password │ false │ false │ false │ false │ │ ├───────────────────────┼────────────────┼───────────────────────┼───────┼───────┼────────┼───────┼──────┤ │ maxscale_admin │ 10.139.158.211 │ mysql_native_password │ false │ false │ false │ false │ │ ├───────────────────────┼────────────────┼───────────────────────┼───────┼───────┼────────┼───────┼──────┤ │ maxscale_admin_role │ │ │ false │ false │ false │ false │ │ ├───────────────────────┼────────────────┼───────────────────────┼───────┼───────┼────────┼───────┼──────┤ │ maxscale_monitor │ 10.139.158.210 │ mysql_native_password │ false │ false │ false │ false │ │ ├───────────────────────┼────────────────┼───────────────────────┼───────┼───────┼────────┼───────┼──────┤ │ maxscale_monitor │ 10.139.158.211 │ mysql_native_password │ false │ false │ false │ false │ │ ├───────────────────────┼────────────────┼───────────────────────┼───────┼───────┼────────┼───────┼──────┤ │ maxscale_monitor_role │ │ │ false │ false │ false │ false │ │ ├───────────────────────┼────────────────┼───────────────────────┼───────┼───────┼────────┼───────┼──────┤ │ mysql │ localhost │ mysql_native_password │ false │ true │ true │ false │ │ ├───────────────────────┼────────────────┼───────────────────────┼───────┼───────┼────────┼───────┼──────┤ │ root │ localhost │ mysql_native_password │ false │ true │ true │ false │ │ └───────────────────────┴────────────────┴───────────────────────┴───────┴───────┴────────┴───────┴──────┘ shell> maxctrl show commands mariadbmon ┌───────────────────────────┬─────────────────────────────┬───────────────────────────────────────────────────────────────────────────────┐ │ Command │ Parameters │ Descriptions │ ├───────────────────────────┼─────────────────────────────┼───────────────────────────────────────────────────────────────────────────────┤ │ switchover │ MONITOR, [SERVER], [SERVER] │ Monitor name, New primary (optional), Current primary (optional) │ ├───────────────────────────┼─────────────────────────────┼───────────────────────────────────────────────────────────────────────────────┤ │ switchover-force │ MONITOR, [SERVER], [SERVER] │ Monitor name, New primary (optional), Current primary (optional) │ ├───────────────────────────┼─────────────────────────────┼───────────────────────────────────────────────────────────────────────────────┤ │ async-switchover │ MONITOR, [SERVER], [SERVER] │ Monitor name, New primary (optional), Current primary (optional) │ ├───────────────────────────┼─────────────────────────────┼───────────────────────────────────────────────────────────────────────────────┤ │ failover │ MONITOR │ Monitor name │ ├───────────────────────────┼─────────────────────────────┼───────────────────────────────────────────────────────────────────────────────┤ │ async-failover │ MONITOR │ Monitor name │ ├───────────────────────────┼─────────────────────────────┼───────────────────────────────────────────────────────────────────────────────┤ │ rejoin │ MONITOR, SERVER │ Monitor name, Joining server │ ├───────────────────────────┼─────────────────────────────┼───────────────────────────────────────────────────────────────────────────────┤ │ async-rejoin │ MONITOR, SERVER │ Monitor name, Joining server │ ├───────────────────────────┼─────────────────────────────┼───────────────────────────────────────────────────────────────────────────────┤ │ reset-replication │ MONITOR, [SERVER] │ Monitor name, Primary server (optional) │ ├───────────────────────────┼─────────────────────────────┼───────────────────────────────────────────────────────────────────────────────┤ │ async-reset-replication │ MONITOR, [SERVER] │ Monitor name, Primary server (optional) │ ├───────────────────────────┼─────────────────────────────┼───────────────────────────────────────────────────────────────────────────────┤ │ release-locks │ MONITOR │ Monitor name │ ├───────────────────────────┼─────────────────────────────┼───────────────────────────────────────────────────────────────────────────────┤ │ async-release-locks │ MONITOR │ Monitor name │ ├───────────────────────────┼─────────────────────────────┼───────────────────────────────────────────────────────────────────────────────┤ │ fetch-cmd-result │ MONITOR │ Monitor name │ ├───────────────────────────┼─────────────────────────────┼───────────────────────────────────────────────────────────────────────────────┤ │ cancel-cmd │ MONITOR │ Monitor name │ ├───────────────────────────┼─────────────────────────────┼───────────────────────────────────────────────────────────────────────────────┤ │ async-cs-add-node │ MONITOR, STRING, STRING │ Monitor name, Hostname/IP of node to add to ColumnStore cluster, Timeout │ ├───────────────────────────┼─────────────────────────────┼───────────────────────────────────────────────────────────────────────────────┤ │ async-cs-remove-node │ MONITOR, STRING, STRING │ Monitor name, Hostname/IP of node to remove from ColumnStore cluster, Timeout │ ├───────────────────────────┼─────────────────────────────┼───────────────────────────────────────────────────────────────────────────────┤ │ cs-get-status │ MONITOR │ Monitor name │ ├───────────────────────────┼─────────────────────────────┼───────────────────────────────────────────────────────────────────────────────┤ │ async-cs-get-status │ MONITOR │ Monitor name │ ├───────────────────────────┼─────────────────────────────┼───────────────────────────────────────────────────────────────────────────────┤ │ async-cs-start-cluster │ MONITOR, STRING │ Monitor name, Timeout │ ├───────────────────────────┼─────────────────────────────┼───────────────────────────────────────────────────────────────────────────────┤ │ async-cs-stop-cluster │ MONITOR, STRING │ Monitor name, Timeout │ ├───────────────────────────┼─────────────────────────────┼───────────────────────────────────────────────────────────────────────────────┤ │ async-cs-set-readonly │ MONITOR, STRING │ Monitor name, Timeout │ ├───────────────────────────┼─────────────────────────────┼───────────────────────────────────────────────────────────────────────────────┤ │ async-cs-set-readwrite │ MONITOR, STRING │ Monitor name, Timeout │ ├───────────────────────────┼─────────────────────────────┼───────────────────────────────────────────────────────────────────────────────┤ │ async-rebuild-server │ MONITOR, SERVER, [SERVER] │ Monitor name, Target server, Source server (optional) │ ├───────────────────────────┼─────────────────────────────┼───────────────────────────────────────────────────────────────────────────────┤ │ async-create-backup │ MONITOR, SERVER, STRING │ Monitor name, Source server, Backup name │ ├───────────────────────────┼─────────────────────────────┼───────────────────────────────────────────────────────────────────────────────┤ │ async-restore-from-backup │ MONITOR, SERVER, STRING │ Monitor name, Target server, Backup name │ └───────────────────────────┴─────────────────────────────┴───────────────────────────────────────────────────────────────────────────────┘
Literatur / Quellen
Taxonomy upgrade extras: shardingmaxscaleschemarouterload balancermulti-tenant

dbstat for MariaDB (and MySQL)

Shinguz - Thu, 2024-03-14 15:36
Table of contents

An idea that I have been thinking about for a long time and have now, thanks to a customer, finally tackled is dbstat for MariaDB/MySQL. The idea is based on sar/sysstat by Sebastien Godard:

sar - Collect, report, or save system activity information.

and Oracle Statspack:

Statspack is a performance tuning tool ... to quickly gather detailed analysis of the performance of that database instance.

Functionality of dbstat

Although we have had the performance schema for some time, it does not cover some points that we see as a problem in practice and that are requested by customers:

  • The table_size module collects data on the growth of tables. This allows statements to be made about the growth of individual tables, databases, future MariaDB Catalogs or the entire instance. This is interesting for users who are using multi-tenant systems or are otherwise struggling with uncontrolled growth.
  • The processlist module takes a snapshot of the process list at regular intervals and saves it. This information is useful for post-mortem analyses if the user was too slow to save his process list or to understand how a problem has built up.
  • The problem is often caused by long-running transactions, row locks or metadata locks. These are recorded and saved by the trx_and_lck and metadata_lock modules. This means that we can see problems that we did not even notice before or we can see what led to the problem after the accident (analogous to a tachograph in a vehicle).
  • Another question that we sometimes encounter in practice is: When was which database variable changed and what did it look like before? This is covered by the global_variables module. Unfortunately, it is not possible to find out who changed the variable or why. Operational processes are required for this.
  • The last module, global_status, actually covers what sar/sysstat does. It collects the values from SHOW GLOBAL STATUS; and saves them for later analysis purposes or to simply create graphs.

How does dbstat work

dbstat uses the database Event Scheduler as a scheduler. This must first be switched on for MariaDB (event_scheduler = ON). With MySQL it is already switched on by default. The Event Scheduler has the advantage that we can activate the jobs at a finer granularity, for example 10 s, which would not be possible with the crontab.

The Event Scheduler then executes SQL/PSM code to collect the data on the one hand and to delete the data on the other, so that the dbstat database does not grow immeasurably.

The following jobs are currently planned:

ModuleCollectDeleteQuantity structureRemarks table_size1/d at 02:0412/h, 1000 rows, > 31 d1000 tab × 31 d = 31k rowsShould work up to 288k tables. processlist1/min1/min, 1000 rows, > 7 d1000 con × 1440 min × 7 d = 10M rowsShould work up to 1000 concurrent connections. trx_and_lck1/min1/min, 1000 rows, > 7 d100 lck × 1440 min × 7 d = 1M rowsDepends very much on the application. metadata_lock1/min12/h, 1000 rows, > 30 d100 mdl × 1440 × 30 d = 4M rowsDepends very much on the application. global_variables1/minnever1000 rowsNormally this table should not grow. global_status1/min1/min, 1000 rows, > 30 d1000 rows × 1440 × 30 d = 40MRows Can become large?
How to install dbstat

dbstat can be downloaded from Github and is licensed under GPLv2.

The installation is simple: First execute the SQL file create_user_and_db.sql. Then execute the corresponding create_*.sql files for the respective modules in the dbstat database. There are currently no direct dependencies between the modules. If you want to use a different user or a different database than dbstat, you have to take care of this yourself.

Query dbstat

Some possible queries on the data have already been prepared. They can be found in the query_*.sql files. Here are a few examples:

table_size SELECT `table_schema`, `table_name`, `ts`, `table_rows`, `data_length`, `index_length` FROM `table_size` WHERE `table_catalog` = 'def' AND `table_schema` = 'dbstat' AND `table_name` = 'table_size' ORDER BY `ts` ASC ; +--------------+------------+---------------------+------------+-------------+--------------+ | table_schema | table_name | ts | table_rows | data_length | index_length | +--------------+------------+---------------------+------------+-------------+--------------+ | dbstat | table_size | 2024-03-09 20:01:00 | 0 | 16384 | 16384 | | dbstat | table_size | 2024-03-10 17:26:33 | 310 | 65536 | 16384 | | dbstat | table_size | 2024-03-11 08:28:12 | 622 | 114688 | 49152 | | dbstat | table_size | 2024-03-12 08:02:38 | 934 | 114688 | 49152 | | dbstat | table_size | 2024-03-13 08:08:55 | 1247 | 278528 | 81920 | +--------------+------------+---------------------+------------+-------------+--------------+
processlist SELECT connection_id, ts, time, state, SUBSTR(REGEXP_REPLACE(REPLACE(query, "\n", ' '), '\ +', ' '), 1, 64) AS query FROM processlist WHERE command != 'Sleep' AND connection_id = @connection_id ORDER BY ts ASC LIMIT 5 ; +---------------+---------------------+---------+---------------------------------+---------------------------------------------+ | connection_id | ts | time | state | query | +---------------+---------------------+---------+---------------------------------+---------------------------------------------+ | 14956 | 2024-03-09 20:21:12 | 13.042 | Waiting for table metadata lock | update test set data = 'bla' where id = 100 | | 14956 | 2024-03-09 20:22:12 | 73.045 | Waiting for table metadata lock | update test set data = 'bla' where id = 100 | | 14956 | 2024-03-09 20:23:12 | 133.044 | Waiting for table metadata lock | update test set data = 'bla' where id = 100 | | 14956 | 2024-03-09 20:24:12 | 193.044 | Waiting for table metadata lock | update test set data = 'bla' where id = 100 | | 14956 | 2024-03-09 20:25:12 | 253.041 | Waiting for table metadata lock | update test set data = 'bla' where id = 100 | +---------------+---------------------+---------+---------------------------------+---------------------------------------------+
trx_and_lck SELECT * FROM trx_and_lck\G *************************** 1. row *************************** machine_name: connection_id: 14815 trx_id: 269766 ts: 2024-03-09 20:05:57 user: root host: localhost db: test command: Query time: 41.000 running_since: 2024-03-09 20:05:16 state: Statistics info: select * from test where id = 6 for update trx_state: LOCK WAIT trx_started: 2024-03-09 20:05:15 trx_requested_lock_id: 269766:821:5:7 trx_tables_in_use: 1 trx_tables_locked: 1 trx_lock_structs: 2 trx_rows_locked: 1 trx_rows_modified: 0 lock_mode: X lock_type: RECORD lock_table_schema: test lock_table_name: test lock_index: PRIMARY lock_space: 821 lock_page: 5 lock_rec: 7 lock_data: 6 *************************** 2. row *************************** machine_name: connection_id: 14817 trx_id: 269760 ts: 2024-03-09 20:05:57 user: root host: localhost db: test command: Sleep time: 60.000 running_since: 2024-03-09 20:04:57 state: info: trx_state: RUNNING trx_started: 2024-03-09 20:04:56 trx_requested_lock_id: NULL trx_tables_in_use: 0 trx_tables_locked: 1 trx_lock_structs: 2 trx_rows_locked: 1 trx_rows_modified: 1 lock_mode: X lock_type: RECORD lock_table_schema: test lock_table_name: test lock_index: PRIMARY lock_space: 821 lock_page: 5 lock_rec: 7 lock_data: 6
metadata_lock SELECT lock_mode, ts, user, host, lock_type, table_schema, table_name, time, started, state, query FROM metadata_lock WHERE connection_id = 14347 ORDER BY started DESC LIMIT 5 ; +-------------------------+---------------------+------+-----------+----------------------+--------------+------------+-------+---------------------+----------------+------------------------------------------------------+ | lock_mode | ts | user | host | lock_type | table_schema | table_name | time | started | state | query | +-------------------------+---------------------+------+-----------+----------------------+--------------+------------+-------+---------------------+----------------+------------------------------------------------------+ | MDL_SHARED_WRITE | 2024-03-13 10:27:33 | root | localhost | Table metadata lock | test | test | 1.000 | 2024-03-13 10:27:32 | Updating | UPDATE test set data3 = MD5(id) | | MDL_BACKUP_TRANS_DML | 2024-03-13 10:27:33 | root | localhost | Backup lock | | | 1.000 | 2024-03-13 10:27:32 | Updating | UPDATE test set data3 = MD5(id) | | MDL_BACKUP_ALTER_COPY | 2024-03-13 10:22:33 | root | localhost | Backup lock | | | 0.000 | 2024-03-13 10:22:33 | altering table | ALTER TABLE test DROP INDEX ts, ADD INDEX (ts, data) | | MDL_SHARED_UPGRADABLE | 2024-03-13 10:22:33 | root | localhost | Table metadata lock | test | test | 0.000 | 2024-03-13 10:22:33 | altering table | ALTER TABLE test DROP INDEX ts, ADD INDEX (ts, data) | | MDL_INTENTION_EXCLUSIVE | 2024-03-13 10:22:33 | root | localhost | Schema metadata lock | test | | 0.000 | 2024-03-13 10:22:33 | altering table | ALTER TABLE test DROP INDEX ts, ADD INDEX (ts, data) | +-------------------------+---------------------+------+-----------+----------------------+--------------+------------+-------+---------------------+----------------+------------------------------------------------------+
global_variables SELECT variable_name, COUNT(*) AS cnt FROM global_variables GROUP BY variable_name HAVING COUNT(*) > 1 ; +-------------------------+-----+ | variable_name | cnt | +-------------------------+-----+ | innodb_buffer_pool_size | 7 | +-------------------------+-----+ SELECT variable_name, ts, variable_value FROM global_variables WHERE variable_name = 'innodb_buffer_pool_size' ; +-------------------------+---------------------+----------------+ | variable_name | ts | variable_value | +-------------------------+---------------------+----------------+ | innodb_buffer_pool_size | 2024-03-09 21:36:28 | 134217728 | | innodb_buffer_pool_size | 2024-03-09 21:40:25 | 268435456 | | innodb_buffer_pool_size | 2024-03-09 21:48:14 | 134217728 | +-------------------------+---------------------+----------------+
global_status SELECT s1.ts , s1.variable_value AS 'table_open_cache_misses' , s2.variable_value AS 'table_open_cache_hits' FROM global_status AS s1 JOIN global_status AS s2 ON s1.ts = s2.ts WHERE s1.variable_name = 'table_open_cache_misses' AND s2.variable_name = 'table_open_cache_hits' AND s1.ts BETWEEN '2024-03-13 11:55:00' AND '2024-03-13 12:05:00' ORDER BY ts ASC ; +---------------------+-------------------------+-----------------------+ | ts | table_open_cache_misses | table_open_cache_hits | +---------------------+-------------------------+-----------------------+ | 2024-03-13 11:55:47 | 1001 | 60711 | | 2024-03-13 11:56:47 | 1008 | 61418 | | 2024-03-13 11:57:47 | 1015 | 62125 | | 2024-03-13 11:58:47 | 1022 | 62829 | | 2024-03-13 11:59:47 | 1029 | 63533 | | 2024-03-13 12:00:47 | 1036 | 64237 | | 2024-03-13 12:01:47 | 1043 | 64944 | | 2024-03-13 12:02:47 | 1050 | 65651 | | 2024-03-13 12:03:47 | 1057 | 66355 | | 2024-03-13 12:04:47 | 1064 | 67059 | +---------------------+-------------------------+-----------------------+
Testing

We have currently rolled out dbstat on our test and production systems to test it and see whether our assumptions regarding stability and calculations of the quantity structure are correct. In addition, using it ourselves is the best way to find out if something is missing or if the handling is impractical (Eat your own dog food).

Sources
Taxonomy upgrade extras: performancemonitoringperformance monitoringmetadata locklocklockingperformance_schema

dbstat für MariaDB (und MySQL)

Oli Sennhauser - Thu, 2024-03-14 11:33
Inhaltsverzeichnis

Eine Idee, die ich schon lange ins Auge gefasst und jetzt endlich, dank eines Kunden, in Angriff genommen habe, ist dbstat für MariaDB/MySQL. Die Idee ist angelehnt an sar/sysstat von Sebastien Godard:

sar - Collect, report, or save system activity information.

und Oracle Statspack:

Statspack is a performance tuning tool ... to quickly gather detailed analysis of the performance of that database instance.

Funktionalität

Zwar haben wir seit längerem das Performance Schema, aber dieses deckt einige Punkte nicht ab, die wir in der Praxis als Problem sehen und von Kunden gewünscht werden:

  • Das Modul table_size sammelt Daten über das Wachstum von Tabellen. Somit können Aussagen über das Wachstum einzelner Tabellen, Datenbanken, die zukünftigen MariaDB Kataloge oder die ganze Instanz gemacht werden. Dies ist interessant für Nutzer welche Multi-Mandanten-Systeme (multi-tenant) im Einsatz oder sonst wie mit unkontrolliertem Wachstum zu kämpfen haben.
  • Das Modul processlist macht in regelmässigen Abständen einen Snapshot der Prozessliste und speichert diese ab. Diese Informationen sind nützlich bei post-mortem Analysen wenn der Nutzer zu langsam war, seine Prozessliste wegzuspeichern oder um zu verstehen, wie sich ein Problem aufgebaut hat.
  • Oft baut sich das Problem durch langlaufende Transaktion, Row Locks oder Metadata Locks auf. Diese werden durch die Module trx_and_lck sowie metadata_lock festgehalten und abgespeichert. Somit können wir Probleme sehen, die wir vorher gar nicht gespürt haben oder wird sehen nach dem Unglück, was zum Problem geführt hat (analog zu einem Fahrtenschreiber im Fahrzeug).
  • Eine weitere Fragestellung, die wir in der Praxis manchmal antreffen, ist: Wann wurde welche Datenbankvariable geändert und wie sah sie vorher aus. Dies wird durch das Modul global_variables abgedeckt. Wer oder warum die Variable geändert hat, kann leider datenbankseitig nicht eruiert werden. Dazu sind betriebliche Prozesse notwendig.
  • Das letzte Modul, global_status deckt eigentlich das ab, was sar/sysstat tut. Es sammelt die Werte von SHOW GLOBAL STATUS; ein und speichert sie ab für spätere Analysezwecke oder um damit einfach Graphen erstellen zu können.

Wie funktioniert dbstat

dbstat nutzt als Scheduler den Datenbank Event Scheduler. Dieser muss bei MariaDB zuerst eingeschaltet werden (event_scheduler = ON). Bei MySQL ist er bereits per default eingeschaltet. Der Event Scheduler hat den Vorteil, dass wir die Jobs feingranularer aktivieren können, zum Beispiel 10 s, was mit der Crontab nicht möglich wäre.

Der Event Scheduler führt dann SQL/PSM Code aus um einerseits die Daten zu sammeln und andererseits die Daten auch wieder zu löschen, damit die dbstat Datenbank nicht ins unermessliche wächst.

Aktuell sind folgende Jobs vorgesehen:

ModulSammelnLöschenMengengerüstBemerkungen table_size1/d um 02:0412/h, 1000 rows, > 31 d1000 tab x 31 d = 31k rowsSollte bis 288k Tabellen funktionieren. processlist1/min1/min, 1000 rows, > 7 d1000 con x 1440 min x 7 d = 10M rowsSollte bis 1000 Concurrent Connections funktionieren. trx_and_lck1/min1/min, 1000 rows, > 7 d100 lck x 1440 min x 7 d = 1M rowsHängt sehr stark von der Anwendung ab. metadata_lock1/min12/h, 1000 rows, > 30 d100 mdl x 1440 x 30 d = 4M rowsHängt sehr stark von der Anwendung ab. global_variables1/minnie1000 rowsIm Normalfall sollte diese Tabelle nicht anwachsen. global_status1/min1/min, 1000 rows, > 30 d1000 rows x 1440 x 30 d = 40M rowsKann gross werden?
Installation

dbstat kann von Github heruntergeladen werden und steht unter der GPLv2.

Die Installation ist einfach: Als erstes die SQL Datei create_user_and_db.sql ausführen. Dann in der Datenbank dbstat die entsprechenden create_*.sql Dateien für die jeweiligen Module ausführen. Es gibt zur Zeit keine direkten Abhängigkeiten zwischen den Modulen. Wenn ein anderer User oder eine andere Datenbank als dbstat verwendet werden soll, muss man sich selber drum kümmern.

Abfrage

Einige mögliche Abfragen auf die Daten wurden bereits vorbereitet. Sie sind zu finden in den Dateien query_*.sql. Hier ein paar Beispiele:

table_size SELECT `table_schema`, `table_name`, `ts`, `table_rows`, `data_length`, `index_length` FROM `table_size` WHERE `table_catalog` = 'def' AND `table_schema` = 'dbstat' AND `table_name` = 'table_size' ORDER BY `ts` ASC ; +--------------+------------+---------------------+------------+-------------+--------------+ | table_schema | table_name | ts | table_rows | data_length | index_length | +--------------+------------+---------------------+------------+-------------+--------------+ | dbstat | table_size | 2024-03-09 20:01:00 | 0 | 16384 | 16384 | | dbstat | table_size | 2024-03-10 17:26:33 | 310 | 65536 | 16384 | | dbstat | table_size | 2024-03-11 08:28:12 | 622 | 114688 | 49152 | | dbstat | table_size | 2024-03-12 08:02:38 | 934 | 114688 | 49152 | | dbstat | table_size | 2024-03-13 08:08:55 | 1247 | 278528 | 81920 | +--------------+------------+---------------------+------------+-------------+--------------+
processlist SELECT connection_id, ts, time, state, SUBSTR(REGEXP_REPLACE(REPLACE(query, "\n", ' '), '\ +', ' '), 1, 64) AS query FROM processlist WHERE command != 'Sleep' AND connection_id = @connection_id ORDER BY ts ASC LIMIT 5 ; +---------------+---------------------+---------+---------------------------------+---------------------------------------------+ | connection_id | ts | time | state | query | +---------------+---------------------+---------+---------------------------------+---------------------------------------------+ | 14956 | 2024-03-09 20:21:12 | 13.042 | Waiting for table metadata lock | update test set data = 'bla' where id = 100 | | 14956 | 2024-03-09 20:22:12 | 73.045 | Waiting for table metadata lock | update test set data = 'bla' where id = 100 | | 14956 | 2024-03-09 20:23:12 | 133.044 | Waiting for table metadata lock | update test set data = 'bla' where id = 100 | | 14956 | 2024-03-09 20:24:12 | 193.044 | Waiting for table metadata lock | update test set data = 'bla' where id = 100 | | 14956 | 2024-03-09 20:25:12 | 253.041 | Waiting for table metadata lock | update test set data = 'bla' where id = 100 | +---------------+---------------------+---------+---------------------------------+---------------------------------------------+
trx_and_lck SELECT * FROM trx_and_lck\G *************************** 1. row *************************** machine_name: connection_id: 14815 trx_id: 269766 ts: 2024-03-09 20:05:57 user: root host: localhost db: test command: Query time: 41.000 running_since: 2024-03-09 20:05:16 state: Statistics info: select * from test where id = 6 for update trx_state: LOCK WAIT trx_started: 2024-03-09 20:05:15 trx_requested_lock_id: 269766:821:5:7 trx_tables_in_use: 1 trx_tables_locked: 1 trx_lock_structs: 2 trx_rows_locked: 1 trx_rows_modified: 0 lock_mode: X lock_type: RECORD lock_table_schema: test lock_table_name: test lock_index: PRIMARY lock_space: 821 lock_page: 5 lock_rec: 7 lock_data: 6 *************************** 2. row *************************** machine_name: connection_id: 14817 trx_id: 269760 ts: 2024-03-09 20:05:57 user: root host: localhost db: test command: Sleep time: 60.000 running_since: 2024-03-09 20:04:57 state: info: trx_state: RUNNING trx_started: 2024-03-09 20:04:56 trx_requested_lock_id: NULL trx_tables_in_use: 0 trx_tables_locked: 1 trx_lock_structs: 2 trx_rows_locked: 1 trx_rows_modified: 1 lock_mode: X lock_type: RECORD lock_table_schema: test lock_table_name: test lock_index: PRIMARY lock_space: 821 lock_page: 5 lock_rec: 7 lock_data: 6
metadata_lock SELECT lock_mode, ts, user, host, lock_type, table_schema, table_name, time, started, state, query FROM metadata_lock WHERE connection_id = 14347 ORDER BY started DESC LIMIT 5 ; +-------------------------+---------------------+------+-----------+----------------------+--------------+------------+-------+---------------------+----------------+------------------------------------------------------+ | lock_mode | ts | user | host | lock_type | table_schema | table_name | time | started | state | query | +-------------------------+---------------------+------+-----------+----------------------+--------------+------------+-------+---------------------+----------------+------------------------------------------------------+ | MDL_SHARED_WRITE | 2024-03-13 10:27:33 | root | localhost | Table metadata lock | test | test | 1.000 | 2024-03-13 10:27:32 | Updating | UPDATE test set data3 = MD5(id) | | MDL_BACKUP_TRANS_DML | 2024-03-13 10:27:33 | root | localhost | Backup lock | | | 1.000 | 2024-03-13 10:27:32 | Updating | UPDATE test set data3 = MD5(id) | | MDL_BACKUP_ALTER_COPY | 2024-03-13 10:22:33 | root | localhost | Backup lock | | | 0.000 | 2024-03-13 10:22:33 | altering table | ALTER TABLE test DROP INDEX ts, ADD INDEX (ts, data) | | MDL_SHARED_UPGRADABLE | 2024-03-13 10:22:33 | root | localhost | Table metadata lock | test | test | 0.000 | 2024-03-13 10:22:33 | altering table | ALTER TABLE test DROP INDEX ts, ADD INDEX (ts, data) | | MDL_INTENTION_EXCLUSIVE | 2024-03-13 10:22:33 | root | localhost | Schema metadata lock | test | | 0.000 | 2024-03-13 10:22:33 | altering table | ALTER TABLE test DROP INDEX ts, ADD INDEX (ts, data) | +-------------------------+---------------------+------+-----------+----------------------+--------------+------------+-------+---------------------+----------------+------------------------------------------------------+
global_variables SELECT variable_name, COUNT(*) AS cnt FROM global_variables GROUP BY variable_name HAVING COUNT(*) > 1 ; +-------------------------+-----+ | variable_name | cnt | +-------------------------+-----+ | innodb_buffer_pool_size | 7 | +-------------------------+-----+ SELECT variable_name, ts, variable_value FROM global_variables WHERE variable_name = 'innodb_buffer_pool_size' ; +-------------------------+---------------------+----------------+ | variable_name | ts | variable_value | +-------------------------+---------------------+----------------+ | innodb_buffer_pool_size | 2024-03-09 21:36:28 | 134217728 | | innodb_buffer_pool_size | 2024-03-09 21:40:25 | 268435456 | | innodb_buffer_pool_size | 2024-03-09 21:41:25 | 268435456 | | innodb_buffer_pool_size | 2024-03-09 21:42:25 | 268435456 | | innodb_buffer_pool_size | 2024-03-09 21:43:25 | 268435456 | | innodb_buffer_pool_size | 2024-03-09 21:44:25 | 268435456 | | innodb_buffer_pool_size | 2024-03-09 21:48:14 | 134217728 | +-------------------------+---------------------+----------------+
global_status SELECT s1.ts , s1.variable_value AS 'table_open_cache_misses' , s2.variable_value AS 'table_open_cache_hits' FROM global_status AS s1 JOIN global_status AS s2 ON s1.ts = s2.ts WHERE s1.variable_name = 'table_open_cache_misses' AND s2.variable_name = 'table_open_cache_hits' AND s1.ts BETWEEN '2024-03-13 11:55:00' AND '2024-03-13 12:05:00' ORDER BY ts ASC ; +---------------------+-------------------------+-----------------------+ | ts | table_open_cache_misses | table_open_cache_hits | +---------------------+-------------------------+-----------------------+ | 2024-03-13 11:55:47 | 1001 | 60711 | | 2024-03-13 11:56:47 | 1008 | 61418 | | 2024-03-13 11:57:47 | 1015 | 62125 | | 2024-03-13 11:58:47 | 1022 | 62829 | | 2024-03-13 11:59:47 | 1029 | 63533 | | 2024-03-13 12:00:47 | 1036 | 64237 | | 2024-03-13 12:01:47 | 1043 | 64944 | | 2024-03-13 12:02:47 | 1050 | 65651 | | 2024-03-13 12:03:47 | 1057 | 66355 | | 2024-03-13 12:04:47 | 1064 | 67059 | +---------------------+-------------------------+-----------------------+
Testen

Zur Zeit haben wir dbstat auf unseren Test- und Produktionssystemen ausgerollt um es zu testen und zu sehen ob unsere Annahmen bezüglich Stabilität und Berechnungen des Mengengerüsts zutreffen. Zudem stellen wir beim selber nutzen am besten fest, wenn es noch was fehlt oder die Handhabung unpraktisch ist (Eat your own dog food).

Quellen
Taxonomy upgrade extras: performancemonitoringperformance monitoringmetadata locklocklockingperformance_schema

MariaDB/MySQL Environment MyEnv 2.1.0 has been released

Shinguz - Wed, 2024-02-28 17:22

FromDual has the pleasure to announce the release of the new version 2.1.0 of its popular MariaDB, Galera Cluster and MySQL multi-instance environment MyEnv.

The new MyEnv can be downloaded here. How to install MyEnv is described in the MyEnv Installation Guide.

In the inconceivable case that you find a bug in the MyEnv please report it to the FromDual bug tracker.

Any feedback, statements and testimonials are welcome as well! Please send them to feedback@fromdual.com.

Upgrade from 1.1.x to 2.0

Please look at the MyEnv 2.0.0 Release Notes.

Upgrade from 2.0.x to 2.1.0 shell> cd ${HOME}/product shell> tar xf /download/myenv-2.1.0.tar.gz shell> rm -f myenv shell> ln -s myenv-2.1.0 myenv
Plug-ins

If you are using plug-ins for showMyEnvStatus create all the links in the new directory structure:

shell> cd ${HOME}/product/myenv shell> ln -s ../../utl/oem_agent.php plg/showMyEnvStatus/
Upgrade of the instance directory structure

From MyEnv 1.0 to 2.0 the directory structure of instances has fundamentally changed. Nevertheless MyEnv 2.0 works fine with MyEnv 1.0 directory structures.

Changes in MyEnv 2.1.0 MyEnv
  • Removed hard coded parts for running MyEnv under O/S user mariadb.
  • Function substitute_path was refactored.
  • Branch guessing improved.
  • Warnings and errors are in color now.
  • MyEnv log file is now touched to avoid problems with O/S user root.
  • O/S user mysql removed in start/stop script.
  • Checks for DB start improved.
  • /var/run replaced by the more modern location /run.
  • Should now be completely MariaDB compatible (mariadbd vs. mysqld).
  • Wrapper mysqld_safe was extended to mariadbd-safe.
  • Replaced getVersionFromMysqld by getVersionAndBranchFromDaemon and extended functionality of this function.
  • LD_LIBRARY_PATH was set to the wrong directory.
  • Reverting Commit: fcc93c5 from v2.0.3 related to CDPATH. Break commands like cd log or cd etc.
  • Database mysql_innodb_cluster_metadata is hidden now.
  • Database #innodb_redo is suppressed now as well for MySQL 8.0, and hideschema is not added to every new instance any more to not overwrite the default.
  • Bug while stopping instance with missing my.cnf fixed.
  • Function getDistribution cleaned-up.
  • MySQL should now also be detected correctly from Ubuntu repository.
  • Function my_exec rewritten.
  • Debian GNU/Linux tag added for distros.
  • Function extractBranch made better to work on Debian and Ubuntu with distribution packages.
  • Oracle Linux is considered as well now.
  • Made scripts ready for new MariaDB behaviour.
  • my.cnf template adapted to newest knowledge.
  • Directory changed from /tmp to /var/tmp, code cleaned-up and renewal, PID file code and message improved in stopInstance.
  • Distributions cleaned-up and cloudlinux, rocky linux and almalinux added as centos compatible distros.

MyEnv Installer
  • Debian 10 and 11 do not support PHP 8.0 yet, fixed.
  • Unit file is copied now correctly.
  • MyEnv instance installation is automatizable now.
  • Instance creation automation added.
  • my.cnf template together with installMyenv should now work without errors or warnings for MariaDB 10.5 - 11.2 and MySQL 8.0 - 8.3.
  • Command yum replaced by dnf.
  • Command apt-get comments replaced by apt.

MyEnv Utilities
  • Client utility adapted in *monitor scripts.
  • InnoDB cluster monitor added.
  • wsrep_last_committed was added in galera_monitor.sh.
  • AWR added, sharding stuff added, lock and trx analysis scripts added.
  • Memory analysis added, NUMA maps output made ready for new variables.
  • connect_maxout utility added.

For subscriptions of commercial use of MyEnv please get in contact with us.

Taxonomy upgrade extras: MyEnvmulti-instancevirtualizationconsolidationSaaSOperationsreleasemysqld_multi

We build a data warehouse from the General Query Log

Shinguz - Wed, 2024-01-31 16:41

The design of a data warehouse differs from relational design. Data warehouses are often designed according to the concept of the star schema.

When building a data warehouse, you usually put the cart before the horse:

  • What questions should my data warehouse be able to answer?
  • How do I have to design my model so that my questions can be answered easily?
  • Where do I get the data to populate the model?
  • How do I fill my model with the data?

For training purposes, we have investigated an issue that arises from time to time with our support team: The system suddenly and unexpectedly starts to behave unusually, nobody has done anything and nobody knows why. Example with a customer last week: The system starts to become unstable at 3 pm, is then restarted hard and then stabilises again from 4 pm...

The easiest thing to do in such a case would be to quickly look at the database with the SHOW PROCESSLIST command and then it often becomes immediately clear where the problem lies. But customers often forget this or they are not fast enough. The General Query Log was already switched on for this customer, so this would be a great case for our General Query Log Data Warehouse!

What questions should my data warehouse be able to answer?

The generic question for this problem should be something like: "Who or what caused my system to behave abnormally?"

In technical terms, the question would be something like:

  • Who: Which user or account was on the database with how many connections at the time in question? What was unusual about it?
  • What: Which queries were running in which schema on the system at the time in question? Which of these queries were unusual?

What should my model look like?

We can already derive some facts and dimensions from the question:

  • User or account (user + host)
  • Time
  • Connections
  • Schema
  • Queries

And this also results in 4 dimensions and the fact table:

Data source

Where the data comes from is relatively easy to answer in this case: The customer provides his General Query Logs or you can also use the General Query Logs of our own systems for testing purposes.

How is the model populated?

Technically, this is known as an ETL process (Extract-Transform-Load). In our case, we have built a General Query Log parser that reads the General Query Log, prepares the data accordingly and saves it in the model.

Checking the model

And then we come to checking the model. We used test data from one of our systems for this:

  • Which user was on the system at the time in question?
  • Which user had how many connections open at the time in question?

SELECT td.time, cd.user, COUNT(*) AS count FROM connection_dim cd JOIN query_fact AS qf ON qf.connection_id = cd.connection_id JOIN time_dim AS td ON td.time_id = qf.time_id JOIN date_dim AS dd ON dd.date_id = qf.date_id WHERE td.time BETWEEN '17:00' AND '18:30' AND dd.date = '2019-08-02' GROUP BY td.time, cd.user ORDER BY td.time ASC, cd.user ; +----------+---------------+-------+ | time | user | count | +----------+---------------+-------+ | 17:58:00 | UNKNOWN USER | 1 | | 17:59:00 | brman | 58 | | 17:59:00 | brman_catalog | 18 | | 17:59:00 | root | 5 | | 18:00:00 | brman | 296 | | 18:00:00 | brman_catalog | 7 | | 18:00:00 | root | 3 | | 18:01:00 | brman_catalog | 18 | | 18:01:00 | root | 3 | | 18:06:00 | brman | 266 | | 18:06:00 | brman_catalog | 6 | | 18:07:00 | brman | 88 | | 18:07:00 | brman_catalog | 7 | | 18:10:00 | brman | 211 | | 18:10:00 | brman_catalog | 18 | | 18:10:00 | root | 4 | | 18:11:00 | brman | 141 | | 18:11:00 | root | 3 | | 18:13:00 | brman | 4 | | 18:14:00 | brman | 348 | | 18:17:00 | brman | 354 | | 18:17:00 | brman_catalog | 12 | | 18:17:00 | root | 1 | +----------+---------------+-------+
  • Which account was on the system at the time in question?
  • Which account had how many connections open at the time in question?

SELECT td.time, cd.user, cd.hostname, COUNT(*) AS count FROM connection_dim cd JOIN query_fact AS qf ON qf.connection_id = cd.connection_id JOIN time_dim AS td ON td.time_id = qf.time_id JOIN date_dim AS dd ON dd.date_id = qf.date_id WHERE td.time BETWEEN '17:00' AND '18:30' AND dd.date = '2019-08-02' GROUP BY td.time, cd.user, cd.hostname ORDER BY td.time ASC, cd.user ; +----------+---------------+--------------+-------+ | time | user | hostname | count | +----------+---------------+--------------+-------+ | 17:58:00 | UNKNOWN USER | UNKNOWN HOST | 1 | | 17:59:00 | brman | localhost | 58 | | 17:59:00 | brman_catalog | localhost | 18 | | 17:59:00 | root | localhost | 5 | | 18:00:00 | brman | localhost | 296 | | 18:00:00 | brman_catalog | localhost | 7 | | 18:00:00 | root | localhost | 3 | | 18:01:00 | brman_catalog | localhost | 18 | | 18:01:00 | root | localhost | 3 | | 18:06:00 | brman | localhost | 266 | | 18:06:00 | brman_catalog | localhost | 6 | | 18:07:00 | brman | localhost | 88 | | 18:07:00 | brman_catalog | localhost | 7 | | 18:10:00 | brman | localhost | 211 | | 18:10:00 | brman_catalog | localhost | 18 | | 18:10:00 | root | localhost | 4 | | 18:11:00 | brman | localhost | 141 | | 18:11:00 | root | localhost | 3 | | 18:13:00 | brman | localhost | 4 | | 18:14:00 | brman | localhost | 348 | | 18:17:00 | brman | localhost | 354 | | 18:17:00 | brman_catalog | localhost | 12 | | 18:17:00 | root | localhost | 1 | +----------+---------------+--------------+-------+
  • What was unusual about it?

SELECT cd.user, td.time, COUNT(*) AS count FROM connection_dim cd JOIN query_fact AS qf ON qf.connection_id = cd.connection_id JOIN time_dim AS td ON td.time_id = qf.time_id JOIN date_dim AS dd ON dd.date_id = qf.date_id WHERE td.time BETWEEN '17:00' AND '18:30' AND dd.date = '2019-08-02' GROUP BY td.time, cd.user ORDER BY cd.user ASC, td.time ASC ; +---------------+----------+-------+ | user | time | count | +---------------+----------+-------+ | brman | 17:59:00 | 58 | | brman | 18:00:00 | 296 | | brman | 18:06:00 | 266 | | brman | 18:07:00 | 88 | | brman | 18:10:00 | 211 | | brman | 18:11:00 | 141 | | brman | 18:13:00 | 4 | | brman | 18:14:00 | 348 | | brman | 18:17:00 | 354 | | brman_catalog | 17:59:00 | 18 | | brman_catalog | 18:00:00 | 7 | | brman_catalog | 18:01:00 | 18 | | brman_catalog | 18:06:00 | 6 | | brman_catalog | 18:07:00 | 7 | | brman_catalog | 18:10:00 | 18 | | brman_catalog | 18:17:00 | 12 | | root | 17:59:00 | 5 | | root | 18:00:00 | 3 | | root | 18:01:00 | 3 | | root | 18:10:00 | 4 | | root | 18:11:00 | 3 | | root | 18:17:00 | 1 | | UNKNOWN USER | 17:58:00 | 1 | +---------------+----------+-------+

One could deduce here, for example, that the user brman had a relatively large number of open connections during the period in question. Whether this is unusual, we have too little data or the time period is too short.

  • Which queries were running on the system at the time in question and in which schema?
  • Which of these queries were unusual?

SELECT sd.schema_name, td.time, SUBSTR(std.statement_text, 1, 128) AS query FROM query_fact AS qf JOIN time_dim AS td ON td.time_id = qf.time_id JOIN schema_dim AS sd ON sd.schema_id = qf.schema_id JOIN statement_dim AS std ON std.statement_id = qf.statement_id WHERE td.time BETWEEN '17:00' AND '18:30' AND sd.schema_name = 'brman_catalog' AND std.command = 'Query' ORDER BY td.time, qf.statement_id LIMIT 10 ; +---------------+----------+----------------------------------------------------------------------------------------------------------------------------------+ | schema_name | time | query | +---------------+----------+----------------------------------------------------------------------------------------------------------------------------------+ | brman_catalog | 17:59:00 | SET NAMES `utf8` | | brman_catalog | 17:59:00 | SELECT COUNT ( * ) AS `cnt` FROM `information_schema` . `tables` WHERE `table_schema` = ? AND TABLE_NAME = ? | | brman_catalog | 17:59:00 | SELECT COUNT ( * ) AS `cnt` FROM `information_schema` . `tables` WHERE `table_schema` = ? AND TABLE_NAME = ? | | brman_catalog | 17:59:00 | CREATE TABLE `metadata` ( `id` TINYINT UNSIGNED NOT NULL AUTO_INCREMENT , `key` VARCHARACTER (?) NOT NULL , `value` VARCHARACTER | | brman_catalog | 17:59:00 | INSERT INTO `metadata` ( `key` , `value` ) VALUES (...) | | brman_catalog | 17:59:00 | INSERT INTO `metadata` ( `key` , `value` ) VALUES (...) | | brman_catalog | 17:59:00 | CREATE TABLE `backups` ( `id` INTEGER UNSIGNED NOT NULL AUTO_INCREMENT , `instance_name` VARCHARACTER (?) NOT NULL , `start_ts` | | brman_catalog | 17:59:00 | CREATE TABLE `backup_details` ( `backup_id` INTEGER UNSIGNED NOT NULL , `hostname` VARCHARACTER (?) NULL , `binlog_file` VARCHAR | | brman_catalog | 17:59:00 | CREATE TABLE `files` ( `id` INTEGER UNSIGNED NOT NULL AUTO_INCREMENT , `schema_name` VARCHARACTER (?) NULL , `original_name` VAR | | brman_catalog | 17:59:00 | CREATE TABLE `binary_logs` ( `id` INTEGER UNSIGNED NOT NULL AUTO_INCREMENT , `filename` VARCHARACTER (?) NOT NULL , `begin_ts` I | +---------------+----------+----------------------------------------------------------------------------------------------------------------------------------+
Suggestions for improvement

Based on this first iteration of the model, you can already see which questions the model cannot yet answer or where the model is too imprecise. This can then be improved in a second round....

Examples of this are:

  • The granularity of the time dimension may be too coarse with an accuracy of minutes. Would it make more sense to use seconds?
  • The question of how long a connection was open is not so easy to answer. Perhaps a further fact table would be appropriate here? SELECT cd.connection_number, cd.user, cd.hostname, tdf.time AS time_from, tdt.time AS time_to, (UNIX_TIMESTAMP(tdt.time) - UNIX_TIMESTAMP(tdf.time)) AS duration FROM connection_dim AS cd JOIN query_fact AS qf1 ON cd.connection_id = qf1.connection_id JOIN time_dim AS tdf ON tdf.time_id = qf1.time_id JOIN statement_dim AS sdf ON sdf.statement_id = qf1.statement_id JOIN query_fact AS qf2 ON cd.connection_id = qf2.connection_id JOIN time_dim AS tdt ON tdt.time_id = qf2.time_id JOIN statement_dim AS sdt ON sdt.statement_id = qf2.statement_id WHERE tdf.time BETWEEN '17:00' AND '18:30' AND sdf.command = 'Connect' AND sdt.command = 'Quit' AND (UNIX_TIMESTAMP(tdt.time) - UNIX_TIMESTAMP(tdf.time)) > 0 ORDER BY tdf.time ; +-------------------+-------+-----------+-----------+----------+----------+ | connection_number | user | hostname | time_from | time_to | duration | +-------------------+-------+-----------+-----------+----------+----------+ | 211 | brman | localhost | 17:59:00 | 18:00:00 | 60 | | 215 | root | localhost | 18:00:00 | 18:17:00 | 1020 | | 219 | brman | localhost | 18:06:00 | 18:07:00 | 60 | | 225 | brman | localhost | 18:10:00 | 18:11:00 | 60 | | 226 | brman | localhost | 18:13:00 | 18:14:00 | 60 | +-------------------+-------+-----------+-----------+----------+----------+
  • Of course, it would be exciting if an AI were used to solve the problem. How do you train it correctly and does it find the problem once it has been trained?

So much for the little gimmick of building a data warehouse...

Taxonomy upgrade extras: data warehousegeneral query log

Wir bauen uns ein Data Warehouse aus dem General Query Log

Oli Sennhauser - Tue, 2024-01-30 16:17

Das Design eines Data Warehouses unterscheidet sich vom relationalen Design. Data Warehouses designt man oft nach dem Konzept des Star Schemas.

Üblicherweise zäumt man beim Bau eines Data Warehouses das Pferd von hinten auf:

  • Welche Fragen soll mein Data Warehouse beantworten können?
  • Wie muss ich mein Modell designen damit sich meine Fragen einfach beantworten lassen?
  • Woher kriege ich die Daten um das Modell zu befüllen?
  • Wie befülle ich mein Model mit den Daten?

Zu Übungszwecken sind wir hier einer Fragestellung nachgegangen, welche ab und zu bei unserem Support auftaucht: Das System fängt plötzlich und unerwartet an sich ungewöhnlich zu verhalten, niemand hat was gemacht und niemand weiss warum. Beispiel bei einem Kunden letzte Woche: Um 15 Uhr fängt das System an instabil zu werden, wird anschliessend hart neu gestartet und stabilisiert sich dann ab 16 Uhr wieder...

Das einfachste wäre es, in einem solchen Fall, schnell mit dem Befehl SHOW PROCESSLIST auf die Datenbank zu schauen und dann wird oft sofort klar, wo das Problem liegt. Aber oft vergessen das die Kunden oder sie sind nicht schnell genug. Bei diesem Kunden war das General Query Log bereits eingeschaltet, das wäre also ein prima Fall für unser General Query Log Data Warehouse!

Welche Fragen soll mein Data Warehouse beantworten können?

Die generische Fragestellung für dieses Problem müsste in etwa lauten: "Wer oder was hat mein System dazu veranlasst, sich ungewöhnlich zu verhalten."

Technisch ausgedrückt würde die Frage in etwa lauten:

  • Wer: Welcher User oder Account war zur fraglichen Zeit mit wie vielen Connections auf der Datenbank drauf? Was war daran ungewöhnlich?
  • Was: Welche Abfragen liefen zur fraglichen Zeit in welchem Schema auf dem System? Welche dieser Abfragen waren ungewöhnlich?

Wie soll mein Modell aussehen?

Aus der Fragestellung können wir bereits einige Fakten und Dimensionen ableiten:

  • User oder Account (User + Host)
  • Zeit
  • Connections
  • Schema
  • Abfragen

Und daraus ergeben sich auch bereit 4 Dimensionen und die Fact-Tabelle:

Datenquelle

Woher die Daten kommen ist in diesem Fall relativ einfach zu beantworten: Der Kunde stellt seine General Query Logs zur Verfügung oder zu Testzwecken kann man auch die General Query Logs unserer eigenen Systeme verwenden.

Wie wird das Modell befüllt?

Technisch geht das unter dem Begriff ETL-Prozess (Extract-Transform-Load). In unserem Fall haben wir einen General Query Log Parser gebaut, der das General Query Log einliest, die Daten entsprechend aufbereitet und im Modell abspeichert.

Überprüfung des Modells

Und dann kommen wir auch schon zur Überprüfung des Modells. Wir haben dazu Testdaten eines unserer Systeme verwendet:

  • Welcher User war zur fraglichen Zeit auf dem System drauf?
  • Welcher User hatte zur fraglichen Zeit wie viel Connections offen?

SELECT td.time, cd.user, COUNT(*) AS count FROM connection_dim cd JOIN query_fact AS qf ON qf.connection_id = cd.connection_id JOIN time_dim AS td ON td.time_id = qf.time_id JOIN date_dim AS dd ON dd.date_id = qf.date_id WHERE td.time BETWEEN '17:00' AND '18:30' AND dd.date = '2019-08-02' GROUP BY td.time, cd.user ORDER BY td.time ASC, cd.user ; +----------+---------------+-------+ | time | user | count | +----------+---------------+-------+ | 17:58:00 | UNKNOWN USER | 1 | | 17:59:00 | brman | 58 | | 17:59:00 | brman_catalog | 18 | | 17:59:00 | root | 5 | | 18:00:00 | brman | 296 | | 18:00:00 | brman_catalog | 7 | | 18:00:00 | root | 3 | | 18:01:00 | brman_catalog | 18 | | 18:01:00 | root | 3 | | 18:06:00 | brman | 266 | | 18:06:00 | brman_catalog | 6 | | 18:07:00 | brman | 88 | | 18:07:00 | brman_catalog | 7 | | 18:10:00 | brman | 211 | | 18:10:00 | brman_catalog | 18 | | 18:10:00 | root | 4 | | 18:11:00 | brman | 141 | | 18:11:00 | root | 3 | | 18:13:00 | brman | 4 | | 18:14:00 | brman | 348 | | 18:17:00 | brman | 354 | | 18:17:00 | brman_catalog | 12 | | 18:17:00 | root | 1 | +----------+---------------+-------+
  • Welcher Account war zur fraglichen Zeit auf dem System drauf?
  • Welcher Account hatte zur fraglichen Zeit wie viel Connections offen?

SELECT td.time, cd.user, cd.hostname, COUNT(*) AS count FROM connection_dim cd JOIN query_fact AS qf ON qf.connection_id = cd.connection_id JOIN time_dim AS td ON td.time_id = qf.time_id JOIN date_dim AS dd ON dd.date_id = qf.date_id WHERE td.time BETWEEN '17:00' AND '18:30' AND dd.date = '2019-08-02' GROUP BY td.time, cd.user, cd.hostname ORDER BY td.time ASC, cd.user ; +----------+---------------+--------------+-------+ | time | user | hostname | count | +----------+---------------+--------------+-------+ | 17:58:00 | UNKNOWN USER | UNKNOWN HOST | 1 | | 17:59:00 | brman | localhost | 58 | | 17:59:00 | brman_catalog | localhost | 18 | | 17:59:00 | root | localhost | 5 | | 18:00:00 | brman | localhost | 296 | | 18:00:00 | brman_catalog | localhost | 7 | | 18:00:00 | root | localhost | 3 | | 18:01:00 | brman_catalog | localhost | 18 | | 18:01:00 | root | localhost | 3 | | 18:06:00 | brman | localhost | 266 | | 18:06:00 | brman_catalog | localhost | 6 | | 18:07:00 | brman | localhost | 88 | | 18:07:00 | brman_catalog | localhost | 7 | | 18:10:00 | brman | localhost | 211 | | 18:10:00 | brman_catalog | localhost | 18 | | 18:10:00 | root | localhost | 4 | | 18:11:00 | brman | localhost | 141 | | 18:11:00 | root | localhost | 3 | | 18:13:00 | brman | localhost | 4 | | 18:14:00 | brman | localhost | 348 | | 18:17:00 | brman | localhost | 354 | | 18:17:00 | brman_catalog | localhost | 12 | | 18:17:00 | root | localhost | 1 | +----------+---------------+--------------+-------+
  • Was war daran ungewöhnlich?

SELECT cd.user, td.time, COUNT(*) AS count FROM connection_dim cd JOIN query_fact AS qf ON qf.connection_id = cd.connection_id JOIN time_dim AS td ON td.time_id = qf.time_id JOIN date_dim AS dd ON dd.date_id = qf.date_id WHERE td.time BETWEEN '17:00' AND '18:30' AND dd.date = '2019-08-02' GROUP BY td.time, cd.user ORDER BY cd.user ASC, td.time ASC ; +---------------+----------+-------+ | user | time | count | +---------------+----------+-------+ | brman | 17:59:00 | 58 | | brman | 18:00:00 | 296 | | brman | 18:06:00 | 266 | | brman | 18:07:00 | 88 | | brman | 18:10:00 | 211 | | brman | 18:11:00 | 141 | | brman | 18:13:00 | 4 | | brman | 18:14:00 | 348 | | brman | 18:17:00 | 354 | | brman_catalog | 17:59:00 | 18 | | brman_catalog | 18:00:00 | 7 | | brman_catalog | 18:01:00 | 18 | | brman_catalog | 18:06:00 | 6 | | brman_catalog | 18:07:00 | 7 | | brman_catalog | 18:10:00 | 18 | | brman_catalog | 18:17:00 | 12 | | root | 17:59:00 | 5 | | root | 18:00:00 | 3 | | root | 18:01:00 | 3 | | root | 18:10:00 | 4 | | root | 18:11:00 | 3 | | root | 18:17:00 | 1 | | UNKNOWN USER | 17:58:00 | 1 | +---------------+----------+-------+

Man könnte hier z.B. ableiten, dass der User brman relativ viele Verbindung in der fraglichen Zeit offen hatte. Ob das ungewöhnlich ist, dazu haben wir zu wenige Daten bzw. dazu ist der Zeitraum zu klein.

  • Welche Abfragen liefen zur fraglichen Zeit in welchem Schema auf dem System?
  • Welche dieser Abfragen waren ungewöhnlich?

SELECT sd.schema_name, td.time, SUBSTR(std.statement_text, 1, 128) AS query FROM query_fact AS qf JOIN time_dim AS td ON td.time_id = qf.time_id JOIN schema_dim AS sd ON sd.schema_id = qf.schema_id JOIN statement_dim AS std ON std.statement_id = qf.statement_id WHERE td.time BETWEEN '17:00' AND '18:30' AND sd.schema_name = 'brman_catalog' AND std.command = 'Query' ORDER BY td.time, qf.statement_id LIMIT 10 ; +---------------+----------+----------------------------------------------------------------------------------------------------------------------------------+ | schema_name | time | query | +---------------+----------+----------------------------------------------------------------------------------------------------------------------------------+ | brman_catalog | 17:59:00 | SET NAMES `utf8` | | brman_catalog | 17:59:00 | SELECT COUNT ( * ) AS `cnt` FROM `information_schema` . `tables` WHERE `table_schema` = ? AND TABLE_NAME = ? | | brman_catalog | 17:59:00 | SELECT COUNT ( * ) AS `cnt` FROM `information_schema` . `tables` WHERE `table_schema` = ? AND TABLE_NAME = ? | | brman_catalog | 17:59:00 | CREATE TABLE `metadata` ( `id` TINYINT UNSIGNED NOT NULL AUTO_INCREMENT , `key` VARCHARACTER (?) NOT NULL , `value` VARCHARACTER | | brman_catalog | 17:59:00 | INSERT INTO `metadata` ( `key` , `value` ) VALUES (...) | | brman_catalog | 17:59:00 | INSERT INTO `metadata` ( `key` , `value` ) VALUES (...) | | brman_catalog | 17:59:00 | CREATE TABLE `backups` ( `id` INTEGER UNSIGNED NOT NULL AUTO_INCREMENT , `instance_name` VARCHARACTER (?) NOT NULL , `start_ts` | | brman_catalog | 17:59:00 | CREATE TABLE `backup_details` ( `backup_id` INTEGER UNSIGNED NOT NULL , `hostname` VARCHARACTER (?) NULL , `binlog_file` VARCHAR | | brman_catalog | 17:59:00 | CREATE TABLE `files` ( `id` INTEGER UNSIGNED NOT NULL AUTO_INCREMENT , `schema_name` VARCHARACTER (?) NULL , `original_name` VAR | | brman_catalog | 17:59:00 | CREATE TABLE `binary_logs` ( `id` INTEGER UNSIGNED NOT NULL AUTO_INCREMENT , `filename` VARCHARACTER (?) NOT NULL , `begin_ts` I | +---------------+----------+----------------------------------------------------------------------------------------------------------------------------------+
Verbesserungsvorschläge

Anhand dieser ersten Iteration des Modells sieht man auch schon, welche Fragen das Modell noch nicht beantworten kann oder wo das Modell zu ungenau ist. Dies kann dann in einer zweiten Rund nachgebessert werden....

Beispiele hierzu sind:

  • Die Granulariät der Dimension time ist mit Minutengenauigkeit möglicherweise zu grob. Sekundengenauigkeit wäre sinnvoller?
  • Die Frage, wie lange eine Connection offen war lässt sich nich so einfach beantworten. Ev. wäre hier eine weiter Fact Tabelle angebracht? SELECT cd.connection_number, cd.user, cd.hostname, tdf.time AS time_from, tdt.time AS time_to, (UNIX_TIMESTAMP(tdt.time) - UNIX_TIMESTAMP(tdf.time)) AS duration FROM connection_dim AS cd JOIN query_fact AS qf1 ON cd.connection_id = qf1.connection_id JOIN time_dim AS tdf ON tdf.time_id = qf1.time_id JOIN statement_dim AS sdf ON sdf.statement_id = qf1.statement_id JOIN query_fact AS qf2 ON cd.connection_id = qf2.connection_id JOIN time_dim AS tdt ON tdt.time_id = qf2.time_id JOIN statement_dim AS sdt ON sdt.statement_id = qf2.statement_id WHERE tdf.time BETWEEN '17:00' AND '18:30' AND sdf.command = 'Connect' AND sdt.command = 'Quit' AND (UNIX_TIMESTAMP(tdt.time) - UNIX_TIMESTAMP(tdf.time)) > 0 ORDER BY tdf.time ; +-------------------+-------+-----------+-----------+----------+----------+ | connection_number | user | hostname | time_from | time_to | duration | +-------------------+-------+-----------+-----------+----------+----------+ | 211 | brman | localhost | 17:59:00 | 18:00:00 | 60 | | 215 | root | localhost | 18:00:00 | 18:17:00 | 1020 | | 219 | brman | localhost | 18:06:00 | 18:07:00 | 60 | | 225 | brman | localhost | 18:10:00 | 18:11:00 | 60 | | 226 | brman | localhost | 18:13:00 | 18:14:00 | 60 | +-------------------+-------+-----------+-----------+----------+----------+
  • Spannend wäre natürlich jetzt noch, wenn man eine KI auf das Problem ansetzt. Wie traniert man sie richtig und findet sie das Problem, wenn sie trainiert wurde?

Soweit die kleine Spielerei zum Bau eines Data Warehouses...

Taxonomy upgrade extras: data warehousegeneral query log

FromDual Performance Monitor for MariaDB 2.1.0 has been released

Shinguz - Sat, 2023-12-09 18:27

FromDual has the pleasure to announce the release of the new version 2.1.0 of its popular Database Performance Monitor for MariaDB and Galera Cluster fpmmm.

The FromDual Performance Monitor for MariaDB (fpmmm) enables DBAs and System Administrators to monitor and understand what is going on inside their MariaDB database instances and on the machines where the databases reside.

More detailed information you can find in the fpmmm Installation Guide.

Download

The new FromDual Performance Monitor for MariaDB (fpmmm) can be downloaded from here or you can use our FromDual repositories. How to install and use fpmmm is documented in the fpmmm Installation Guide.

In the inconceivable case that you find a bug in the FromDual Performance Monitor for MariaDB please report it to the FromDual Bug-tracker or just send us an email.

Any feedback, statements and testimonials are welcome as well! Please send them to us.

Monitoring as a Service (MaaS)

You do not want to set-up your Database monitoring yourself? No problem: Choose our MariaDB Monitoring as a Service (Maas) program to safe time and costs!

Installation of Performance Monitor 2.1.0

A complete guide on how to install FromDual Performance Monitor you can find in the fpmmm Installation Guide.

Upgrade of fpmmm tarball from 1.x to 2.1.0

There are some changes in the configuration file (fpmmm.conf):

  • The access rights should be change as follows: chmod 600 /etc/fpmmm.conf
  • The key Methode was spelled wrong in the configuration file. It was renamed to Method.
  • The key PidFile is ambiguous which could lead to problems and bugs. Thus it was changed to either MyPidFile for fpmmm and DbPidFile for the database.

Upgrade with DEB/RPM packages should happen automatically. For tarballs follow this:

shell> cd /opt shell> tar xf /download/fpmmm-2.1.0.tar.gz shell> rm -f fpmmm shell> ln -s fpmmm-2.1.0 fpmmm
Changes in FromDual Performance Monitor for MariaDB 2.1.0

This release contains new features and various bug fixes.

You can verify your current FromDual Performance Monitor for MariaDB version with the following command:

shell> /opt/fpmmm/bin/fpmmm --version
General
  • Comments and some more debugging information added.
  • All needed logging added for tracking down the problem of bad stat output.
  • New variables fixed.
  • Error messages improved.
  • Fix error output.
  • Version 10.11.1 was not split up correctly, fixed.
  • myEnv updated to fix bad MySQL detection on Ubuntu from repository.
  • Old database version error fixed if connection to API does not work.
  • Disable smart module by default to avoid error messages.
  • Removed /etc/fpmmm folder everywhere.
  • rc made unique, tests fixed.
  • Default path locations brought up to date.
  • DbPidFile location is new under /run.
  • All tests for MariaDB 10.11 passed.
  • CacheFileBase bug fixed.
  • FreeDSx/SNMP upgraded from 0.4 to 0.5.
  • DB connection handling improved and made more OO style.
  • Configuration file parser made more stable for syntax errors.
  • Error log logged to systemd message improved.
  • Option --version is now done before check options.
  • PHP requirement version specified.

Templates
  • Templates improved.
  • Link for triggers fixed.
  • Working period added to all graphs.
  • Zabbix 6 templates added to Makefile.
  • Zabbix 6.0 templates added (6.0.21) and renamed.

Agent
  • All variables from templates removed, test added for fpmmm MRRELEASE.
  • Fix MRRLEASE tag in fpmmm template fixed again.
  • Function writeDataToCache improved for tracking customer problems.
  • CacheFile is now protected with flock, this should resolve issues with lost brman items.
  • fpmmm version problem error message improved.
  • Disabled = True is not recognized correctly and no error was thrown. This is fixed now.
  • Messages were not handled correctly with SNMP output. This is fixed now.
  • mdstat message removed from error log.
  • Make error messages around sending data nicer.
  • apt-get/yum messages replaced by dnf/apt.
  • Error message made more clear if php-cli package is missing.

Server
  • Trigger too many filesystem locks set from MULTIPLE to SINGLE, threshold increased from 10000 to 16384 (mariadb MaxNOFiles) and message improved.
  • Working time added to server graphs.
  • iostat items remove from server template.
  • Available disks are now reported with space in between.
  • Disk sda5 removed from template, network interfaces enp4s0f1 and bond0 added to template, disks vdb1 and md1 added to template.
  • CPU usage details removed, guest_nice item added.
  • Swapping items added.
  • Typo in host screen fixed.

Galera
  • Galera group replication latency added.
  • In addition to old wsrep_causal_reads the new wsrep_sync_wait variable was added including the trigger.
  • Non Galera node is not detected as such and gives ugly error message, fixed.

InnoDB
  • Item innodb log write requests and innodb log writes fixed in innodb template.
  • Item InnoDB Trx Log bytes written renamed to InnoDB Log bytes written, graph InnoDB Log Activity removed because it is redundant now.
  • Item innodb_redo_log_capacity added for MySQL 8.0.
  • InnoDB buffer pool wait free trigger has wrong filter for item. fixed.
  • InnoDB Buffer Pool wait for free pages trigger added link to item value.
  • innodb_file_format also removed from template.
  • InnoDB buffer pool wait free trigger added.
  • FromDual.MySQL.innodb.Innodb_data_pending_fsyncs changed from absolute values to change_per_second to make graph useful.
  • Links fixed in triggers for innodb module.

MySQL
  • DB is soon out of support message downgraded from average to warning.
  • Item name fixed.
  • Link for table open cache trigger adjusted.
  • Trigger for mysql/mariadb support ends was changed from multiple to single to reduce noise.
  • com_call_procedure status counter fixed in module and template.
  • storage_engine item remove from template, processlist item waiting for table level lock fixed.
  • TOC was updated in template and improved and cleaned-up.
  • Unlock table item is not collected any more and trigger was removed, caused useless alerts.
  • Modern TOC handling implemented.

Process
  • Process module refactored, more logging and tests added.
  • Bug in process module fixed: /proc/PID/stat was not parsed correctly.

Security
  • Links fixed in triggers for security module.

Master
  • Binlog event count and binlog avg event size removed from master template because we cannot calculate those values.

Backup
  • Backup template duration URL fixed.

Packaging
  • Packages added for Debian 10, Debian 11, Debian 12, Ubuntu 20.04, Ubuntu 22.04, Redhat 8 and Redhat 9.
  • Package bug with fpmmm.ini fixed.
  • Debian build version increased and package build config error fixed again.
  • Debian package revision introduced.
  • Bug in config copy during postinst fixed.
  • Package installation error overwriting fpmmm.conf fixed.

For subscriptions of commercial use of fpmmm please get in contact with us.

Taxonomy upgrade extras: performancemonitormonitoringfpmmmmaasreleaseobservation

InnoDB Deadlock on SELECT? Not possible! Or Is It?

Shinguz - Sat, 2023-11-25 16:58
Introduction

Two points in advance:

  1. A deadlock is a state in which two different transactions are no longer able to continue working because each transaction holds a lock that the other transaction would need. Because both transactions are now waiting for the other transaction to release their locks, neither transaction will release their respective locks. And that would last forever. To avoid this, the MariaDB instance intervenes and kills the transaction that has done less work. The application then receives a deadlock error message of this type:
    ERROR 1213 (40001): Deadlock found when trying to get lock; try restarting transaction
  2. A general mantra in the MariaDB ecosystem is that a SELECT does not cause locks (exception: FOR UPDATE or LOCK IN SHARE MODE) and therefore cannot be part of a deadlock.

The problem

A long-standing customer comes to the FromDual remote DBA team with a request to explain a deadlock situation:

Hello FromDual Team,
I need your expertise on the subject of deadlocks.
When would it suit you?


The situation is as follows: Transaction 1 consists of a simple INSERT. Transaction 2 consists of a SELECT. This should NOT actually cause a deadlock!

We first check the following points

  • Are all tables affected by these queries properly indexed? Yes, they are. The queries are all running perfectly!
  • Is the SELECT query possibly part of a larger transaction (NOT an auto-commit transaction) and therefore not the actual cause of the deadlock? No, it is not. They are auto-commit transactions.

What now? What else needs to be said for clarification: The SELECT is sent with a very high cadence, i.e. approx. every 5 ms!

It is clear that the INSERT generates locks. It is also displayed. But why does the SELECT command generate locks? These are also displayed!

So we try to break the problem down into individual steps.

The approach

The query looks like this:

SQL> SET @id = (SELECT id FROM test WHERE id = 3);

If we pack this query into an explicit transaction, we can even see the locks:

SQL> START TRANSACTION; SQL> SET @id = (SELECT id FROM test WHERE id = 3);

and in a second session:

SQL> SELECT * FROM information_schema.INNODB_TRX\G *************************** 1. row *************************** trx_id: 0 trx_state: RUNNING trx_started: 2023-11-19 15:27:09 trx_requested_lock_id: NULL trx_wait_started: NULL trx_weight: 2 trx_mysql_thread_id: 3765 trx_query: NULL trx_operation_state: trx_tables_in_use: 0 trx_tables_locked: 1 trx_lock_structs: 2 trx_lock_memory_bytes: 1128 trx_rows_locked: 1 trx_rows_modified: 0 trx_concurrency_tickets: 0 trx_isolation_level: REPEATABLE READ trx_unique_checks: 1 trx_foreign_key_checks: 1 trx_last_foreign_key_error: NULL trx_is_read_only: 0 trx_autocommit_non_locking: 0

Unfortunately, we cannot see what kind of lock (IS) it is, because the view INNODB_LOCKS is empty.

The solution

If we do the same experiment with "normal" SELECTs:

SQL> START TRANSACTION; SELECT id FROM test WHERE id = 3;

or

SQL> START TRANSACTION; SELECT id INTO @id FROM test WHERE id = 3;

we do NOT see any locks:

SQL> SELECT * FROM information_schema.INNODB_TRX\G *************************** 1. row *************************** trx_id: 0 trx_state: RUNNING trx_started: 2023-11-19 15:31:35 trx_requested_lock_id: NULL trx_wait_started: NULL trx_weight: 0 trx_mysql_thread_id: 3765 trx_query: NULL trx_operation_state: trx_tables_in_use: 0 trx_tables_locked: 0 trx_lock_structs: 0 trx_lock_memory_bytes: 1128 trx_rows_locked: 0 trx_rows_modified: 0 trx_concurrency_tickets: 0 trx_isolation_level: REPEATABLE READ trx_unique_checks: 1 trx_foreign_key_checks: 1 trx_last_foreign_key_error: NULL trx_is_read_only: 0 trx_autocommit_non_locking: 0

So it seems that the construct SET @id = (...) causes this IS lock. The customer rewrites his application and shortly afterwards we receive the following message:

Hello FromDual team,
Your tip was spot on.
No more deadlocks since Friday lunchtime.
Thank you and have a nice weekend.


Further clarified questions

MySQL 8.0 behaves the same? Yes, exactly the same.

Addendum

My dear colleague Matthias gave me a follow-up idea: What about MariaDB Stored Procedures and Stored Functions?

The two tests here:

DELIMITER // CREATE OR REPLACE PROCEDURE locktestsp (INOUT id INT) BEGIN SELECT id INTO id FROM test WHERE id = id LIMIT 1; END; // DELIMITER ; SET @id = 3; START TRANSACTION; CALL locktestsp(@id); SELECT @id; SELECT trx_tables_locked, trx_lock_structs, trx_rows_locked FROM information_schema.INNODB_TRX; +-------------------+------------------+-----------------+ | trx_tables_locked | trx_lock_structs | trx_rows_locked | +-------------------+------------------+-----------------+ | 0 | 0 | 0 | +-------------------+------------------+-----------------+

and here:

DELIMITER // CREATE OR REPLACE FUNCTION locktestsf (IN id INT) RETURNS CHAR(50) DETERMINISTIC BEGIN SELECT id INTO id FROM test WHERE id = id LIMIT 1; RETURN id; END; // DELIMITER ; START TRANSACTION; SELECT locktestsf(3); SELECT trx_tables_locked, trx_lock_structs, trx_rows_locked FROM information_schema.INNODB_TRX; +-------------------+------------------+-----------------+ | trx_tables_locked | trx_lock_structs | trx_rows_locked | +-------------------+------------------+-----------------+ | 0 | 0 | 0 | +-------------------+------------------+-----------------+
Translated by deepl.com

InnoDB Deadlock bei SELECT? Nicht möglich! Oder doch?

Oli Sennhauser - Sun, 2023-11-19 16:18
Einleitung

Kurz vorab zwei Punkte:

  1. Ein Deadlock ist eine Zustand, in welchem 2 unterschiedliche Transaktionen nicht mehr in der Lage sind weiter zu arbeiten, weil jede Transaktion jeweils einen Lock hält, welche die andere Transaktion gerade bräuchte. Weil jetzt beide Transaktionen jeweils darauf warten, bis die andere Transaktion ihren Lock wieder frei gibt, wird keine von beiden Transaktionen ihre jeweiligen Locks wieder frei geben. Und das würde bis zum Sankt-Nimmerleins-Tag andauern. Um das zu vermeiden schreitet die MariaDB Instanz ein und killt kurzerhand diejenige Transaktion, die weniger Arbeit geleistet hat. Die Applikation kriegt darauf hin eine Deadlock Fehlermeldung vom Typ:
    ERROR 1213 (40001): Deadlock found when trying to get lock; try restarting transaction
  2. Im MariaDB Ökosystem gilt allgemein das Mantra, dass ein SELECT keine Locks verursacht (Ausnahme: FOR UPDATE oder LOCK IN SHARE MODE) und somit auch nicht Teil eines Deadlocks sein kann.

  3. Das Problem

    Ein langjähriger Kunde kommt zum FromDual remote-DBA Team mit der Bitte, eine Deadlock-Situation zu erklären:

    Hallo FromDual Team,
    ich brauche mal wieder euer Fachwissen zum Thema Deadlocks.
    Wann würde es Euch passen?


    Die Situation ist folgende: Transaktion 1 besteht aus einem simplen INSERT. Transaktion 2 besteht aus einem SELECT. Das dürfte eigentlich KEINEN Deadlock verursachen!

    Zuerst prüfen wir folgende Punkte ab:

  • Sind alle Tabellen, die durch diese Abfragen betroffen sind, sauber indexiert? Jawohl sind sie. Die Queries laufen alle perfekt!
  • Ist die SELECT Abfragen eventuell Teil einer grösseren Transaktion (NICHT Auto-Commit Transaktion) und daher nicht die eigentlich Ursache für den Deadlock? Nein, ist sie nicht. Es handelt sich um Auto-Commit Transaktionen.

Was nun? Was man zur Erläuterung noch sagen muss: Das SELECT wird mit einer sehr hohen Kadenz, also so ca. alle 5 ms abgesetzt!

Dass der INSERT Locks erzeugt ist klar. Wird ja auch angezeigt. Aber warum erzeugt der SELECT Befehl Locks? Diese werden ebenfalls angezeigt!

Also versuchen wir das Problem in Einzelschritte runter zu brechen.

Der Lösungsweg

Das Query sieht wie folgt aus:

SQL> SET @id = (SELECT id FROM test WHERE id = 3);

Wenn wir dieses Query in eine explizite Transaktion packen, können wir die Locks sogar sehen:

SQL> START TRANSACTION; SQL> SET @id = (SELECT id FROM test WHERE id = 3);

und in einer zweiten Session:

SQL> SELECT * FROM information_schema.INNODB_TRX\G *************************** 1. row *************************** trx_id: 0 trx_state: RUNNING trx_started: 2023-11-19 15:27:09 trx_requested_lock_id: NULL trx_wait_started: NULL trx_weight: 2 trx_mysql_thread_id: 3765 trx_query: NULL trx_operation_state: trx_tables_in_use: 0 trx_tables_locked: 1 trx_lock_structs: 2 trx_lock_memory_bytes: 1128 trx_rows_locked: 1 trx_rows_modified: 0 trx_concurrency_tickets: 0 trx_isolation_level: REPEATABLE READ trx_unique_checks: 1 trx_foreign_key_checks: 1 trx_last_foreign_key_error: NULL trx_is_read_only: 0 trx_autocommit_non_locking: 0

Leider sehen wir nicht welche Art von Lock (IS) es ist, da die View INNODB_LOCKS leer ist.

Die Lösung

Wenn wir den selben Versuch mit "normalen" SELECTs machen:

SQL> START TRANSACTION; SELECT id FROM test WHERE id = 3;

oder

SQL> START TRANSACTION; SELECT id INTO @id FROM test WHERE id = 3;

sehen wir KEINE Locks:

SQL> SELECT * FROM information_schema.INNODB_TRX\G *************************** 1. row *************************** trx_id: 0 trx_state: RUNNING trx_started: 2023-11-19 15:31:35 trx_requested_lock_id: NULL trx_wait_started: NULL trx_weight: 0 trx_mysql_thread_id: 3765 trx_query: NULL trx_operation_state: trx_tables_in_use: 0 trx_tables_locked: 0 trx_lock_structs: 0 trx_lock_memory_bytes: 1128 trx_rows_locked: 0 trx_rows_modified: 0 trx_concurrency_tickets: 0 trx_isolation_level: REPEATABLE READ trx_unique_checks: 1 trx_foreign_key_checks: 1 trx_last_foreign_key_error: NULL trx_is_read_only: 0 trx_autocommit_non_locking: 0

Es scheint also so zu sein, dass das Konstrukt SET @id = (...) diesen IS Lock verursacht. Der Kunde schreibt seine Applikation um und kurz darauf erhalten wir folgende Meldung:

Hallo FromDual Team,
Euer Tipp war goldrichtig.
Seit Freitag Mittag keine Deadlocks mehr.
Danke und schönes Wochenende.


Weitere geklärte Fragen

MySQL 8.0 verhält sich gleich? Ja, genau gleich.

Webinar: Upgrade Ihres MySQL 5.7 Galera Clusters auf MySQL 8.0 ohne Ausfallzeiten

Oli Sennhauser - Thu, 2023-11-16 11:34

Sie haben sicher schon davon gehört, dass MySQL 5.7 im Oktober 2023 das End of Life (EOL) erreicht hat. In diesem Webinar zeigen wir Ihnen, dass die Migration von MySQL 5.7 Galera Cluster nicht schwierig ist. MySQL 8.0 ist seit 5 Jahren allgemein verfügbar, und das Galera Cluster für MySQL 8.0 hat sich seit über 3 Jahren im Markt bewährt. Es ist also wirklich an der Zeit, sich auf die Migration vorzubereiten.

Im ersten Webinar dieser Reihe werden wir uns mit den neuen Funktionen von Galera Cluster mit MySQL 8 befassen:

  • Die neuen Funktionen von Galera Cluster für MySQL 8, von denen Sie profitieren können, einschliesslich der in der Galera Cluster Enterprise Edition (EE) verfügbaren Funktionen
  • Wie man eine Migration von MySQL 5.7 auf MySQL 8.0 plant
  • Dinge, die vor der Migration getestet werden sollten
  • Häufige Fallstricke bei einer solchen Migration
  • Wie Sie sicherstellen, dass Ihr Galera Cluster während der Migration ohne Ausfallzeiten weiterläuft

Das Webinar findet am Freitag, 17. November 2023, 9:00 - 10:00 MEZ statt.

Für das Webinar können Sie sich hier registrieren.

Präsentatoren:
Oli Sennhauser, Fromdual
Sakari Keskitalo, Codership, the developers of Galera Cluster

Über Galera Cluster Support Subskriptionen und Migrations-Support informieren wir sie gerne persönlich. Bitte wenden Sie sich an uns, wir helfen Ihnen gerne weiter.

Bitte senden Sie Ihre Fragen, Anmerkungen und Ihr Feedback an: contact@fromdual.com

Mit freundlichen Grüssen,
Ihr FromDual Team

Upgrading MariaDB to the pre-latest minor release

Shinguz - Wed, 2023-02-08 13:45

Scenario: MariaDB Community Server is release every 3 months. The exact date is not known but it is typically about 2 to 3 weeks after the MySQL/Oracle CPU.

We upgrade regularly customer systems, also their MariaDB Galera Cluster systems. Because we made in the past some very bad experience upgrading production MariaDB Galera Clusters short after release date we became a bit more careful. Our new policy is: We wait a few weeks before installing a new release.

This week we had the situation that on Monday a new MariaDB release came out and on Wednesday we had to do the Cluster upgrade. So only 2 days in between. Too short time for my taste. But we did not want to omit the upgrade because it was already more than 6 months since the last upgrade...

So we decided to install the pre-latest MariaDB release. Technically it means: Customer was on 10.6.9, 10.6.12 is out (and already available in the repositories) but we want to upgrade to 10.6.11. Additionally we also wanted to upgrade the O/S (Debian 11). So how to do this quite complex task? In short:

  • Set all MariaDB related packages to hold.
  • Upgrade all other packages including a reboot of the machine.
  • Unhold all MariaDB related packages.
  • Install specific MariaDB packages which are not the newest one.

Set MariaDB related packages to hold dpkg -l | grep mariadb ii libdbd-mariadb-perl 1.21-3 amd64 Perl5 database interface to the MariaDB/MySQL databases ii libmariadb3:amd64 1:10.6.9+maria~deb11 amd64 MariaDB database client library ii libmariadb3-compat 1:10.6.9+maria~deb11 amd64 MariaDB database client library MySQL compat package ii libmariadbclient18 1:10.6.9+maria~deb11 amd64 Virtual package to satisfy external libmariadbclient18 depends ii mariadb-client-10.6 1:10.6.9+maria~deb11 amd64 MariaDB database client binaries ii mariadb-client-core-10.6 1:10.6.9+maria~deb11 amd64 MariaDB database core client binaries ii mariadb-common 1:10.6.9+maria~deb11 all MariaDB common configuration files ii mariadb-server-10.6 1:10.6.9+maria~deb11 amd64 MariaDB database server binaries ii mariadb-server-core-10.6 1:10.6.9+maria~deb11 amd64 MariaDB database core server files apt-mark hold galera-4 libmariadb3-compat libmariadb3 libmariadbclient18 mariadb-client-10.6 mariadb-client-core-10.6 mariadb-common mariadb-server-10.6 mariadb-server-core-10.6 mysql-common apt-mark showhold
Upgrade al other O/S dependent packages apt update apt list --upgradable Listing... Done galera-4/unknown 26.4.14-deb11 amd64 [upgradable from: 26.4.11-0+deb11u1] libmariadb3-compat/unknown 1:10.6.12+maria~deb11 amd64 [upgradable from: 1:10.6.9+maria~deb11] libmariadb3/unknown 1:10.6.12+maria~deb11 amd64 [upgradable from: 1:10.6.9+maria~deb11] libmariadbclient18/unknown 1:10.6.12+maria~deb11 amd64 [upgradable from: 1:10.6.9+maria~deb11] libssl1.1/stable-security 1.1.1n-0+deb11u4 amd64 [upgradable from: 1.1.1n-0+deb11u3] mariadb-client-10.6/unknown 1:10.6.12+maria~deb11 amd64 [upgradable from: 1:10.6.9+maria~deb11] mariadb-client-core-10.6/unknown 1:10.6.12+maria~deb11 amd64 [upgradable from: 1:10.6.9+maria~deb11] mariadb-common/unknown 1:10.6.12+maria~deb11 all [upgradable from: 1:10.6.9+maria~deb11] mariadb-server-10.6/unknown 1:10.6.12+maria~deb11 amd64 [upgradable from: 1:10.6.9+maria~deb11] mariadb-server-core-10.6/unknown 1:10.6.12+maria~deb11 amd64 [upgradable from: 1:10.6.9+maria~deb11] mysql-common/unknown 1:10.6.12+maria~deb11 all [upgradable from: 5.8+1.0.7] openssl/stable-security 1.1.1n-0+deb11u4 amd64 [upgradable from: 1.1.1n-0+deb11u3] apt upgrade The following packages have been kept back: galera-4 libmariadb3 libmariadb3-compat libmariadbclient18 mariadb-client-10.6 mariadb-client-core-10.6 mariadb-common mariadb-server-10.6 mariadb-server-core-10.6 mysql-common The following packages will be upgraded: libssl1.1 openssl 2 upgraded, 0 newly installed, 0 to remove and 10 not upgraded. cat /var/run/reboot-required # reboot [-f]
Unhold MariaDB related packages apt-mark unhold galera-4 libmariadb3-compat libmariadb3 libmariadbclient18 mariadb-client-10.6 mariadb-client-core-10.6 mariadb-common mariadb-server-10.6 mariadb-server-core-10.6 mysql-common apt-mark showhold
Install specific MariaDB version packages apt list -a galera-4 apt install galera-4=26.4.13-bullseye libmariadb3-compat=1:10.6.11+maria~deb11 libmariadb3=1:10.6.11+maria~deb11 libmariadbclient18=1:10.6.11+maria~deb11 mariadb-client-10.6=1:10.6.11+maria~deb11 mariadb-client-core-10.6=1:10.6.11+maria~deb11 mariadb-common=1:10.6.11+maria~deb11 mariadb-server-10.6=1:10.6.11+maria~deb11 mariadb-server-core-10.6=1:10.6.11+maria~deb11 mysql-common=1:10.6.11+maria~deb11 # To avoid 2 database restarts we can also do the reboot here systemctl restart mariadb mariadb-upgrade --user=root apt list --upgradable Listing... Done galera-4/unknown 26.4.14-deb11 amd64 [upgradable from: 26.4.13-bullseye] libmariadb3-compat/unknown 1:10.6.12+maria~deb11 amd64 [upgradable from: 1:10.6.11+maria~deb11] libmariadb3/unknown 1:10.6.12+maria~deb11 amd64 [upgradable from: 1:10.6.11+maria~deb11] libmariadbclient18/unknown 1:10.6.12+maria~deb11 amd64 [upgradable from: 1:10.6.11+maria~deb11] mariadb-client-10.6/unknown 1:10.6.12+maria~deb11 amd64 [upgradable from: 1:10.6.11+maria~deb11] mariadb-client-core-10.6/unknown 1:10.6.12+maria~deb11 amd64 [upgradable from: 1:10.6.11+maria~deb11] mariadb-common/unknown 1:10.6.12+maria~deb11 all [upgradable from: 1:10.6.11+maria~deb11] mariadb-server-10.6/unknown 1:10.6.12+maria~deb11 amd64 [upgradable from: 1:10.6.11+maria~deb11] mariadb-server-core-10.6/unknown 1:10.6.12+maria~deb11 amd64 [upgradable from: 1:10.6.11+maria~deb11] mysql-common/unknown 1:10.6.12+maria~deb11 all [upgradable from: 1:10.6.11+maria~deb11]
Taxonomy upgrade extras: debianpackageupgradelocklockingholdpin

FromDual Ops Center 1.2.1 for MariaDB, MySQL and compatible databases has been released

Shinguz - Tue, 2023-02-07 17:08

FromDual has the pleasure to announce the release of the new version 1.2.1 of its popular FromDual Ops Center focmm, a Graphical User Interface (GUI) for MariaDB, MySQL and compatible databases.

The FromDual Ops Center for MariaDB and MySQL (focmm) helps DBA's and System Administrators to better manage their MariaDB and MySQL databases and Galera Cluster farms. Ops Center makes DBA and Admins life easier!

The main task of Ops Center is to support you in your daily MariaDB and MySQL operation tasks. More information about FromDual Ops Center you can find under General Information.

Download

The new FromDual Ops Center for MariaDB and MySQL (focmm) can be downloaded from our download site. How to install and use focmm is documented in the Ops Center User Guide.

In the inconceivable case that you find a bug in the FromDual Ops Center for MariaDB and MySQL please report it to the FromDual bug tracker or just send us an email.

Any feedback, statements and testimonials are welcome as well! Please send them to feedback@fromdual.com.

Installation of Ops Center 1.2.1

Information on how to install FromDual Ops Center you can find in the Ops Center User Guide.

Upgrade from 0.9.x to 1.2.1

Upgrade from 0.9.x to 1.2.1 should happen automatically. Please do a backup of your Ops Center database instance before you upgrade! Please also check Upgrading.

Changes in Ops Center 1.2.1 Machine
  • ssh "Suspect machine" message fix advice command is now done with the right user and file.
  • Check error fixed and output made nicer.
  • Instance link added in machine overview and code clean-up.
  • Gather machine information added after add instance and before create instance to make sure O/S and distribution information is always there when instance is added or created.
  • Code clean-up in machine refresh.
  • Resource Group tag fixed, and code clean-up in machine show settings.

Instance
  • Repository connection was closed too early in starting and stopping instance. So start/stop failed. Bug fixed.
  • Case is caught properly now where node is started but galera plugin was not activated.
  • Bug in deploy configuration fixed. When " was added the configuration file was cut.
  • Bug in stopping instance fixed. Instance could not be stopped any more.

Cluster
  • Configuration wsrep_on = on is for MariaDB Galera Cluster and made now default. It was missing in some cases.

Load Balancer
  • GLB error handling and error messages improved.
  • Load balancer naming is enforced to unique now and load balancer configuration deployment message added.

Virtual IP (VIP)/Floating IP
  • No changes.

Tools
  • Job: Variable was not initialized correctly (bin/*), fixed.

Configuration
  • No changes.
Database-as-a-Service (DBaaS)
  • More debug information added to catch error in pricing calculations.

Building and Packaging
  • Debian compat level increased from 9 to 13.

Themes / UI
  • Library jquery updated from 3.6.1 to 3.6.3.
  • Field titles made unique Resource Group.

General
  • Some tests improved and frags made more robust.
  • Bugs in catch section fixed.
  • _SERVER[PHP_SELF] in some cases lead to wrong destination, fixed.

Repository
  • No changes.

Taxonomy upgrade extras: OperationsreleaseFromDual Ops Centerops centerdbaasfocmm

FromDual Ops Center 1.2.0 for MariaDB, MySQL and compatible databases has been released

Shinguz - Thu, 2023-01-19 12:01

FromDual has the pleasure to announce the release of the new version 1.2.0 of its popular FromDual Ops Center focmm, a Graphical User Interface (GUI) for MariaDB, MySQL and compatible databases.

The FromDual Ops Center for MariaDB and MySQL (focmm) helps DBA's and System Administrators to better manage their MariaDB and MySQL databases and Galera Cluster farms. Ops Center makes DBA and Admins life easier!

The main task of Ops Center is to support you in your daily MariaDB and MySQL operation tasks. More information about FromDual Ops Center you can find under General Information.

Download

The new FromDual Ops Center for MariaDB and MySQL (focmm) can be downloaded from our download site. How to install and use focmm is documented in the Ops Center User Guide.

In the inconceivable case that you find a bug in the FromDual Ops Center for MariaDB and MySQL please report it to the FromDual bug tracker or just send us an email.

Any feedback, statements and testimonials are welcome as well! Please send them to feedback@fromdual.com.

Installation of Ops Center 1.2.0

Information on how to install FromDual Ops Center you can find in the Ops Center User Guide.

Upgrade from 0.9.x to 1.2.0

Upgrade from 0.9.x to 1.2.0 should happen automatically. Please do a backup of your Ops Center database instance before you upgrade! Please also check Upgrading.

Changes in Ops Center 1.2.0 Machine
  • Delete machine error message improved.
  • Add machine made more user friendly.
  • Delete machine warning message made more verbose.
  • Error handling improved and error messages made more verbose in gathering machine information.

Instance
  • Create instance: InnoDB buffer pool size estimation fixed.
  • Remove -core- packages from installation selection.
  • Access keys added to show instance.
  • Instance and machine names are sorted in selection now.
  • Error handling improved in performance views.
  • Restart instance bug fixed,
  • Status cluster_conf_id added.
  • Galera node bootstrap is shown correctly now.
  • Create schema can do character set now.
  • Start instance refactored.
  • Create instance is also working for Debian now.
  • Restart instance implemented.
  • Repository instance cannot be stopped any more to avoid system outages.
  • Processlist rewritten to P_S.threads.
  • Some more performance views added.
  • Delete instance warning message made more verbose.
  • Create instance: Machine names are sorted now alphabetically.
  • Query Cache remove in create instance because MySQL 8.0 does not support it any more and it is by default off in MariaDB now.
  • Instance backup remembers brman path now.

Cluster
  • Galera safe_to_bootstrap is working now and can be forced.
  • Cluster weight, node weight and segment added for Galera.
  • More information in error message when saving cluster.
  • Master/Slave features are not shown any more if Galera Cluster is chosen.
  • Cluster type cannot be changed any more.
  • Galera disable buttons if instance is stopped.
  • Galera node bootstrap functionality implemented.
  • Galera Cluster configuration deployment implemented.
  • Galera Cluster does not show M/S features any more.
  • Replication operations: SQL thread state was not displayed correctly.
  • GTID related information added to replication operations.
  • Delete instance from cluster made a bit more user friendly.

Load Balancer
  • Some minor bugs in load balancer and VIP failover fixed.
  • Galera Load Balancer balancing policy fixed.
  • Page made more user friendly.
  • Galera Load Balancer restart implemented.
  • Operations for MariaDB MaxScale implemented.
  • Load Balancer socket variable normalized.
  • Delete Load Balancer implemented.
  • Galera Load Balancer configuration is backuped before saving.
  • Galera Load Balancer Load Balancer policy change implemented.
  • Load Balancer policy added.
  • Change weight of load balancer back-end added.
  • Galera Load Balancer configuration persist added.
  • Galera Load Balancer load balancer configuration file parsed and displayed under settings.
  • Galera Load Balancer drain and undrain back-end added.
  • Galera Load Balancer version added to operations.
  • Galera Load Balancer checks refresh every 10 seconds.
  • Galera Load Balancer start and stop implemented
  • Statistics for Galera Load Balancer added.
  • Operations overview for Galera Load Balancer added.
  • Operations menu enabled.

Virtual IP (VIP)/Floating IP
  • VIP failover problem fixed.
  • Bitmask /32 is wrong, was changed to /24.
  • VIP failover made more robust.
  • Deploy standard keepalived configuration implemented.
  • keepalived version added.
  • keepalived failover works fine.
  • keepalived failover is working now.
  • vip keepalived failover started.
  • keepalived stop and start added.
  • Checks for keepalived added.
  • keepalived flag for vip added.
  • VIP can now be kept under keepalived.

Tools
  • Back button remove from crontab, makes no sense here.
  • Read in readJobs fixed and some error messages improved.
  • Display limited to 100 jobs because of memory issues.
  • Bug with remaining my_exec.stderr.* files found and fixed. PID 0 kill was caught, mkdir locking replaced by flock locking.

Configuration
  • No changes.
Database-as-a-Service (DBaaS)
  • No changes.

Building and Packaging
  • .ssh directory is created also on RPM.
  • MariaDB added as default for Rocky8.
  • Syntax error in installation script fixed.
  • On Rocky9 httpd and mysqld is now started during package installation.
  • php-mysql replaced by php-mysqlnd for RHEL package.
  • RPM package building added.
  • Directory .ssh for repository user is created during installation.
  • Package lsb-release added to Debian.
  • Install error message made better for Debian.

Themes / UI
  • jquery updated from 3.6.0 to 3.6.1 and jquery ui themes from 1.12.1 to 1.13.2

General
  • Changed copyright year from 2022 to 2023.
  • Some PHP 8.1 deprecations fixed.
  • Repository DB handle added to all writecheck functions.
  • PHP function exec replaced by my_exec where possible (ssh, scp).
  • whoami fixed, PATH added to my_exec because of Rocky8.
  • Function checkBinary also made working locally on Rocky8.
  • Bug in testEmail fixed.
  • Distribution Debian GNU/Linux is now supported everywhere.
  • Apache mod_rewrite enabled by default.
  • Add Apache SSL to installation.
  • Menu is now controllable via keys.
  • FromDual software versions is added.
  • Error message more verbose in case sendmail is not installed (Debian).
  • myEnv library updated including distro clean-up.
  • Better IP guessing during installation.

Repository
  • Create repository fixed for mariadb 5.5.
  • Code clean-up for focmm configuration file operations.

Taxonomy upgrade extras: OperationsreleaseFromDual Ops Centerops centerdbaasfocmm

MariaDB und MySQL Schulungsprogramm 2023

Oli Sennhauser - Tue, 2023-01-17 16:24

Auch im Jahr 2023 haben Sie wieder die Möglichkeit, sich bei unseren 3 Schulungspartnern in Essen, Köln und Berlin MariaDB und MySQL seitig fit zu machen.

Folgende Termine können wir Ihnen für das Jahr 2023 schon jetzt anbieten:

  • 30. Januar bis 3. Februar 2023: MariaDB/MySQL für Fortgeschrittene, GFU Schulungszentrum, Köln
  • 27. Februar bis 3. März 2023: MariaDB/MySQL für Fortgeschrittene, Heinlein Akademie, Berlin
  • 20. bis 24. März 2023: MariaDB/MySQL für Fortgeschrittene, Linuxhotel, Essen
  • 27. bis 29. März 2023: Galera Cluster für MariaDB/MySQL, GFU Schulungszentrum, Köln
  • 24. bis 28. April 2023: MariaDB/MySQL für Fortgeschrittene, GFU Schulungszentrum, Köln
  • 3. bis 5. Mai 2023: Galera Cluster für MariaDB/MySQL, Linuxhotel, Essen
  • 15. bis 17. Mai 2023: Galera Cluster für MariaDB/MySQL, Heinlein Akademie, Berlin
  • 5. bis 7. Juni 2023: Galera Cluster für MariaDB/MySQL, GFU Schulungszentrum, Köln
  • 24. bis 28. Juli 2023: MariaDB/MySQL für Fortgeschrittene, GFU Schulungszentrum, Köln
  • 11. bis 15. September 2023: MariaDB/MySQL für Fortgeschrittene, Heinlein Akademie, Berlin
  • 25. bis 27. September 2023: Galera Cluster für MariaDB/MySQL, GFU Schulungszentrum, Köln
  • 23. bis 27. Oktober 2023: MariaDB/MySQL für Fortgeschrittene, GFU Schulungszentrum, Köln
  • 6. bis 8. November 2023: Galera Cluster für MariaDB/MySQL, Linuxhotel, Essen
  • 13. bis 15. November 2023: Galera Cluster für MariaDB/MySQL, Heinlein Akademie, Berlin
  • 27. November bis 1. Dezember 2023: MariaDB/MySQL für Fortgeschrittene, Linuxhotel, Essen
  • 4. bis 6. Dezember 2023: Galera Cluster für MariaDB/MySQL, GFU Schulungszentrum, Köln

Diese Schulungen können online gebucht werden.

Weitere Termine können während des Jahres noch hinzukommen.

Bei Fragen, oder wenn Sie Spezialwünsche haben, stehen wir Ihnen gerne mit Rat und Tat zur Seite! Zögern Sie nicht, uns zu kontaktieren, wir helfen Ihnen gerne per eMail weiter.

Bei allen weiteren Galera, MariaDB und MySQL Problemen oder Fragen unterstützen wir Sie natürlich ebenfalls gerne!

Mit freundlichen Grüssen,
Ihr FromDual Team

Quellen: Bild von StartupStockPhotos auf Pixabay

Taxonomy upgrade extras: schulungtrainingseminar2023mysqlmariadbgaleramysql schulungmariadb schulunggalera schulung

Comparing Optimizer Results

Shinguz - Fri, 2022-11-18 10:59

A while ago I read a paper about Optimizer Benchmarks: How Good Are Query Optimizers, Really? by Viktor Leis from Fakultät für Informatik of the Technische Universität München.

Because we have from time to time problems with slow queries of customers especially after upgrading to new database releases it is interesting for me, how different optimizers cope with a query. Sometimes it is not clear to me why the query is slow or how I can make it faster. So the mentioned paper inspired me to compare the same query with the same dataset among different optimizers or optimizer versions. The most recent query from our customer we were testing against MariaDB 10.6, 10.9, 10.10, MySQL 8.0 and PostgreSQL 15.1. The test data

The table we were using is our generic test table which many people already know from our MariaDB and MySQL trainings:

CREATE TABLE `test` ( `id` int(10) unsigned NOT NULL AUTO_INCREMENT, `data` varchar(128) DEFAULT NULL, `ts` timestamp NOT NULL DEFAULT current_timestamp() ON UPDATE current_timestamp(), PRIMARY KEY (`id`) );
Loading the data from MySQL

How to dump the data from MySQL to load them into PostgreSQL I have already described earlier. This is about how to create the table and load the data into PostgreSQL:

# sudo su - postgres # psql # postgres=# SELECT VERSION(); # postgres=# \l # postgres=# CREATE DATABASE test; CREATE DATABASE postgres=# \c test postgres=# CREATE TABLE test ( id SERIAL NOT NULL PRIMARY KEY, data VARCHAR(128) DEFAULT NULL, ts TIMESTAMP NOT NULL ); test=# \dt+ List of relations Schema | Name | Type | Owner | Persistence | Access method | Size | Description --------+----------+-------+----------+-------------+---------------+---------+------------- public | test | table | postgres | permanent | heap | 0 bytes | # psql test < /tmp/test_dump.sql
The Query

The query we had problems with looked something like this:

WITH t AS ( SELECT SUM(id)+0.0 AS c, data AS pn FROM test WHERE ts BETWEEN '2022-11-22 00:00:00' AND '2022-11-22 23:59:59' AND data LIKE 'ab%' GROUP BY data ORDER BY data -- MariaDB 10.6: 0.66s -- MariaDB 10.9: 0.37s -- Competing product: 0.70s ) SELECT 'AAA' AS label, ((SELECT c FROM t WHERE pn = 'ab06d9ca0e5eb27e5bb2e5c0f345b782')+(SELECT c FROM t WHERE pn = 'ab0f8e861348995d1cbf9ec21d4bf52d'))/((SELECT c FROM t WHERE pn = 'ab134910f6808802cf44b587fb825ab5')+(SELECT c FROM t WHERE pn = 'ab1d6682feb41a97054e8c634ecd5552'))*100 AS value -- MariaDB 10.6: 2.04s -- MariaDB 10.9: 0.79s -- Competing product: 0.70s UNION SELECT 'BBB' AS label, (SELECT c FROM t WHERE pn = 'ab2516b576d7463f106b5671bdac6d32')/((SELECT c FROM t WHERE pn = 'ab28e05f4fa736f4738a2ff6cf494f04')+(SELECT c FROM t WHERE pn = 'ab31ab6a7d52fee49990d63dee58371b'))*100 AS value -- MariaDB 10.6: 3.54s -- MariaDB 10.9: 1.38s -- Competing product: 0.70s UNION SELECT 'CCC' AS label, (SELECT c FROM t WHERE pn = 'ab390b211d7bb3cc19fc1f808fb1bc3a')/(SELECT c FROM t WHERE pn = 'ab45af9e4ca10d3a618d40ec3f230349')*100 AS value -- MariaDB 10.6: 4.58s -- MariaDB 10.9: 1.76s -- Competing product: 0.70s UNION SELECT 'DDD' AS label, ((SELECT c FROM t WHERE pn = 'ab531756624d8287d38eb5fe5809bdb4')+(SELECT c FROM t WHERE pn = 'ab5aaa230cc64c15a61f908aea1c3f9c'))/((SELECT c FROM t WHERE pn = 'ab60f7712cd176b6ac26040d69be0e11')+(SELECT c FROM t WHERE pn = 'ab674e464997f4916e7ed23942c53d23'))*100 AS value UNION SELECT 'EEE' AS label, (SELECT c FROM t WHERE pn = 'ab6cc3781441a08d67eb8039521c63bb')/((SELECT c FROM t WHERE pn = 'ab7612bca85db4f6c4638a658fbee646')+(SELECT c FROM t WHERE pn = 'ab7811882f520c2051c6761edf4c306f'))*100 AS value UNION SELECT 'FFF' AS label, (SELECT c FROM t WHERE pn = 'ab7f0bd3758fbdac0ff6abb24db166ad')/(SELECT c FROM t WHERE pn = 'ab87d7d598ad47ca5db3bf9e6cbdee48')*100 AS value -- MariaDB 10.6: 9.15s -- MariaDB 10.9: 3.51s -- Competing product: 0.71s ;
The results

Timing is enabled in PostgreSQL as follows:

postgres=# \timing

Then we were running the different queries against the different databases and versions:

 Q1Q2Q3Q4Q5Q6 MariaDB 10.6.110.14 s0.32 s0.79 s1.39 s1.78 s3.56 s MariaDB 10.9.40.14 s0.33 s0.80 s1.40 s1.80 s3.60 s MariaDB 10.10.20.14 s0.33 s0.80 s1.39 s1.78 s3.55 s MySQL 8.0.310.03 s0.77 s0.77 s0.77 s0.77 s0.77 s PostgreSQL 15.10.03 s0.04 s0.04 s0.04 s0.04 s0.04 s
The Queries Query 1: SELECT COUNT(*) FROM test;
Query 2 SELECT SUM(id)+0.0 AS c, data AS pn FROM test WHERE ts BETWEEN '2022-11-22 00:00:00' AND '2022-11-22 23:59:59' AND data LIKE 'ab%' GROUP BY data ORDER BY data;
Query 3 WITH t AS ( SELECT SUM(id)+0.0 AS c, data AS pn FROM test WHERE ts BETWEEN '2022-11-22 00:00:00' AND '2022-11-22 23:59:59' AND data LIKE 'ab%' GROUP BY data ORDER BY data ) SELECT 'AAA' AS label, ((SELECT c FROM t WHERE pn = 'ab06d9ca0e5eb27e5bb2e5c0f345b782')+(SELECT c FROM t WHERE pn = 'ab0f8e861348995d1cbf9ec21d4bf52d'))/((SELECT c FROM t WHERE pn = 'ab134910f6808802cf44b587fb825ab5')+(SELECT c FROM t WHERE pn = 'ab1d6682feb41a97054e8c634ecd5552'))*100 AS value;
Query 4 WITH t AS ( SELECT SUM(id)+0.0 AS c, data AS pn FROM test WHERE ts BETWEEN '2022-11-22 00:00:00' AND '2022-11-22 23:59:59' AND data LIKE 'ab%' GROUP BY data ORDER BY data ) SELECT 'AAA' AS label, ((SELECT c FROM t WHERE pn = 'ab06d9ca0e5eb27e5bb2e5c0f345b782')+(SELECT c FROM t WHERE pn = 'ab0f8e861348995d1cbf9ec21d4bf52d'))/((SELECT c FROM t WHERE pn = 'ab134910f6808802cf44b587fb825ab5')+(SELECT c FROM t WHERE pn = 'ab1d6682feb41a97054e8c634ecd5552'))*100 AS value UNION SELECT 'BBB' AS label, (SELECT c FROM t WHERE pn = 'ab2516b576d7463f106b5671bdac6d32')/((SELECT c FROM t WHERE pn = 'ab28e05f4fa736f4738a2ff6cf494f04')+(SELECT c FROM t WHERE pn = 'ab31ab6a7d52fee49990d63dee58371b'))*100 AS value;
Query 5 WITH t AS ( SELECT SUM(id)+0.0 AS c, data AS pn FROM test WHERE ts BETWEEN '2022-11-22 00:00:00' AND '2022-11-22 23:59:59' AND data LIKE 'ab%' GROUP BY data ORDER BY data ) SELECT 'AAA' AS label, ((SELECT c FROM t WHERE pn = 'ab06d9ca0e5eb27e5bb2e5c0f345b782')+(SELECT c FROM t WHERE pn = 'ab0f8e861348995d1cbf9ec21d4bf52d'))/((SELECT c FROM t WHERE pn = 'ab134910f6808802cf44b587fb825ab5')+(SELECT c FROM t WHERE pn = 'ab1d6682feb41a97054e8c634ecd5552'))*100 AS value UNION SELECT 'BBB' AS label, (SELECT c FROM t WHERE pn = 'ab2516b576d7463f106b5671bdac6d32')/((SELECT c FROM t WHERE pn = 'ab28e05f4fa736f4738a2ff6cf494f04')+(SELECT c FROM t WHERE pn = 'ab31ab6a7d52fee49990d63dee58371b'))*100 AS value UNION SELECT 'CCC' AS label, (SELECT c FROM t WHERE pn = 'ab390b211d7bb3cc19fc1f808fb1bc3a')/(SELECT c FROM t WHERE pn = 'ab45af9e4ca10d3a618d40ec3f230349')*100 AS value;
Query 6 WITH t AS ( SELECT SUM(id)+0.0 AS c, data AS pn FROM test WHERE ts BETWEEN '2022-11-22 00:00:00' AND '2022-11-22 23:59:59' AND data LIKE 'ab%' GROUP BY data ORDER BY data ) SELECT 'AAA' AS label, ((SELECT c FROM t WHERE pn = 'ab06d9ca0e5eb27e5bb2e5c0f345b782')+(SELECT c FROM t WHERE pn = 'ab0f8e861348995d1cbf9ec21d4bf52d'))/((SELECT c FROM t WHERE pn = 'ab134910f6808802cf44b587fb825ab5')+(SELECT c FROM t WHERE pn = 'ab1d6682feb41a97054e8c634ecd5552'))*100 AS value UNION SELECT 'BBB' AS label, (SELECT c FROM t WHERE pn = 'ab2516b576d7463f106b5671bdac6d32')/((SELECT c FROM t WHERE pn = 'ab28e05f4fa736f4738a2ff6cf494f04')+(SELECT c FROM t WHERE pn = 'ab31ab6a7d52fee49990d63dee58371b'))*100 AS value UNION SELECT 'CCC' AS label, (SELECT c FROM t WHERE pn = 'ab390b211d7bb3cc19fc1f808fb1bc3a')/(SELECT c FROM t WHERE pn = 'ab45af9e4ca10d3a618d40ec3f230349')*100 AS value UNION SELECT 'DDD' AS label, ((SELECT c FROM t WHERE pn = 'ab531756624d8287d38eb5fe5809bdb4')+(SELECT c FROM t WHERE pn = 'ab5aaa230cc64c15a61f908aea1c3f9c'))/((SELECT c FROM t WHERE pn = 'ab60f7712cd176b6ac26040d69be0e11')+(SELECT c FROM t WHERE pn = 'ab674e464997f4916e7ed23942c53d23'))*100 AS value UNION SELECT 'EEE' AS label, (SELECT c FROM t WHERE pn = 'ab6cc3781441a08d67eb8039521c63bb')/((SELECT c FROM t WHERE pn = 'ab7612bca85db4f6c4638a658fbee646')+(SELECT c FROM t WHERE pn = 'ab7811882f520c2051c6761edf4c306f'))*100 AS value UNION SELECT 'FFF' AS label, (SELECT c FROM t WHERE pn = 'ab7f0bd3758fbdac0ff6abb24db166ad')/(SELECT c FROM t WHERE pn = 'ab87d7d598ad47ca5db3bf9e6cbdee48')*100 AS value;
Conclusion

This little tests showed some results I have not expected:

  • MariaDB Optimizer does some bad things on this query. OK, this was expected. Bug is reported: MDEV-30017.
  • The originally very bad execution times from MariaDB 10.6 (see timing notes in the first query) were not reproducible any more the next day. I should consider more to run ANALYZE TABLE. I should have know this because it is not the first time I experienced this.
  • We have a lot of variations between different measurements. This I should investigate a bit more later...
  • In the MariaDB Server Fest 2022 yesterday I heard with MariaDB 11 Optimizer everything will become much better... Wait! there is something more I do not understand and which I did not expect:
  • PostgreSQL response time is constantly dramatic better for these queries. I checked the docu but did not find anything beside their normal cache which would explain this (something similar to the MariaDB Query Cache for example). If somebody has a clue why they manage to respond so fast or why we respond so slow I would be happy for a hint...

Taxonomy upgrade extras: postgresqlOptimizerperformanceresponse timelatency

Migration of your data from one database to another

Shinguz - Thu, 2022-11-17 17:01

Before you consider migrating your data from MySQL to another database you have to know which objects have to be migrated.

With this query you will find the objects to consider:

SELECT TABLE_SCHEMA AS `SCHEMA`, IF(TABLE_TYPE = 'BASE TABLE', 'TABLE', TABLE_TYPE) AS OBJECT_TYPE, TABLE_NAME AS `OBJECT_NAME` , IFNULL(ENGINE, '') AS ENGINE, IFNULL(TABLE_ROWS, '') AS `ROWS` , IFNULL(DATA_LENGTH, '') AS DATA_SIZE, IFNULL(INDEX_LENGTH, '') AS INDEX_SIZE FROM information_schema.tables WHERE TABLE_SCHEMA NOT IN ('information_schema', 'mysql', 'performance_schema', 'sys') UNION SELECT '', IF(is_role = 'Y', 'ROLE', 'USER'), CONCAT("'", user, "'", '@', "'", host, "'") AS OBJECT_TYPE, '', '', '', '' FROM mysql.user UNION SELECT db, type, name, '', '', '', '' FROM mysql.proc WHERE db NOT IN ('sys', 'information_schema', 'performance_schema', 'mysql') UNION SELECT db, 'EVENT', name, '', '', '', '' FROM mysql.event UNION SELECT trigger_schema, 'TRIGGER', trigger_name, '', '', '', '' FROM information_schema.triggers UNION SELECT db, 'EVENT', name, '', '', '', '' FROM mysql.event ORDER BY `SCHEMA` ASC, OBJECT_TYPE ASC, OBJECT_NAME ASC ; +--------+-------------+---------------------------+--------+---------+-----------+------------+ | SCHEMA | OBJECT_TYPE | OBJECT_NAME | ENGINE | ROWS | DATA_SIZE | INDEX_SIZE | +--------+-------------+---------------------------+--------+---------+-----------+------------+ | | ROLE | 'test_r'@'' | | | | | | | USER | 'app'@'%' | | | | | | | USER | 'app'@'127.0.0.1' | | | | | | | USER | 'focmm'@'127.0.0.1' | | | | | | | USER | 'test'@'localhost' | | | | | | sbtest | TABLE | sbtest1 | InnoDB | 9680 | 2637824 | 163840 | | test | EVENT | myevent | | | | | | test | FUNCTION | format_time | | | | | | test | PROCEDURE | diagnostics | | | | | | test | TABLE | dt | InnoDB | 6 | 16384 | 0 | | test | TABLE | test | InnoDB | 1045044 | 63520768 | 0 | | test | TRIGGER | test_trigger | | | | | | test | VIEW | test_v | | | | | +--------+-------------+---------------------------+--------+---------+-----------+------------+

An easy way to dump all the object definitions (except users and roles) is the following command:

mysqldump --user=root --no-data test > /tmp/test_structure_dump.sql

If you want to dump your data for importing them into another SQL database this command can help:

mysqldump --user=root --skip-extended-insert --skip-lock-tables --no-create-info \ --where='id = id ' --skip-add-locks --skip-comments --skip-quote-names test test \ | grep -v '^/\*' | grep -v ^$ > /tmp/test_dump.sql
Taxonomy upgrade extras: migrationdatabase

Linux Container with LXD for focmm unit testing

Shinguz - Thu, 2022-10-13 19:11

Currently we are in the testing phase of the next release of our Ops Center (focmm). This testing is quite complex because it includes testing the interaction of various different components like a MariaDB Galera Cluster, a Galera Load Balancer, a virtual IP, etc.

Recently I was in the Linuxhotel for a Galera Cluster Training and there one of the other trainers was romanticising about Linux Containers and LXD. So I had a short look, if LXD could be useful to simplify our unit testing. Some old knowledge from a previous Docker PoC was quite helpful to start with...

Prepare a LXC container for Galera Load Balancer

This did NOT work as expected because the Debian image was lacking IPv4 addresses and I did not find on the quick how to change that. So I used the Ubuntu 22.04 image.

shell> lxc remote list shell> lxc image list images: ubuntu/22.04 amd64 shell> INSTANCE='qa-glb' shell> lxc launch images:ubuntu/jammy ${INSTANCE} shell> lxc list *glb* +--------+---------+-----------------------+----------------------------------------------+------------+-----------+ | NAME | STATE | IPV4 | IPV6 | TYPE | SNAPSHOTS | +--------+---------+-----------------------+----------------------------------------------+------------+-----------+ | qa-glb | RUNNING | 10.139.158.183 (eth0) | fd42:1730:178f:78c:216:3eff:fe3f:2948 (eth0) | PERSISTENT | 0 | +--------+---------+-----------------------+----------------------------------------------+------------+-----------+

Now we should remember the IPv4 address for later use. I am sure this can be done more elegant but for now this is fine...

Install Galera Load Balancer in the LXC container shell> lxc exec ${INSTANCE} -- /bin/bash container> apt-get update container> apt-get install wget container> wget https://support.fromdual.com/admin/download/glb_1.0.1-Ubuntu12.04-x86_64.deb container> apt-get install ./glb_1.0.1-Ubuntu12.04-x86_64.deb container> rm -f glb_1.0.1-Ubuntu12.04-x86_64.deb

Then we have to add the unit file:

# # /etc/systemd/system/glb.service # [Unit] Description=Galera Load Balancer Service After=network.target [Service] EnvironmentFile=/etc/default/glbd Type=simple ExecStart=/usr/local/sbin/glbd --daemon --threads $THREADS --max_conn $MAX_CONN $OTHER_OPTIONS --control $CONTROL_ADDR $LISTEN_ADDR $DEFAULT_TARGETS [Install] WantedBy=multi-user.target

enable the unit file, configure the Galera Load Balancer and start it:

container> systemctl enable glb # Galera Load Balancer Configuration # Redhat: /etc/sysconfig/glbd # Debian: /etc/default/glbd LISTEN_ADDR="3306" CONTROL_ADDR="10.139.158.183:8011" CONTROL_FIFO="/var/run/glbd.fifo" THREADS="2" MAX_CONN=151 DEFAULT_TARGETS="10.139.158.1:3330:1 10.139.158.1:3331:1 10.139.158.1:3332:1" OTHER_OPTIONS="--round" container> systemctl start glb container> apt-get remove wget
Container testing

To be sure everything works fine we should do some basic tests:

shell> lxc stop ${INSTANCE} shell> lxc start ${INSTANCE} shell> echo getinfo | nc -q 1 10.139.158.183 8011
Unit testing focmm against Galera Load Balancer in the LXC container

And finally we did the unit testing of focmm against the Galera Local Balancer which is in the LXC container:

shell> ./tst/run_all_tests.php --instance=qamariadb106 --module=LoadBalancer shell>/dev/null Environment is: qamariadb106 Logfile is: /tmp/focmm_tst_qamariadb106.log Tests are: module=LoadBalancer and function=all OK stopLoadBalancerRemote OK startLoadBalancerRemote OK restartLoadBalancerRemote OK readLoadBalancerTypes OK createLoadBalancer OK updateLoadBalancer OK readLoadBalancers OK parseGlbConfiguration OK openSocket OK writeReadSocket OK parseGlbGetInfo OK parseGlbGetStats OK changeLoadBalancerBackendWeightRemote OK deleteLoadBalancer
Taxonomy upgrade extras: containerlxclxdtestingunit testinggaleraload balancer

Zusätzliche Galera Cluster Schulung im Dezember 2022

Oli Sennhauser - Mon, 2022-10-10 16:40

Aufgrund der grossen Nachfrage bieten wir vom 19. bis 22. Dezember 2022 ein zusätzliches Galera Cluster Seminar an. Dies in Zusammenarbeit mit unserem Schulungspartner, der GfU Cyrus AG in Köln.

Dieses Seminar wird remote durchgeführt. Sie können an diesem Seminar also bequem von zuhause aus teilnehmen...

Eine Seminarübersicht finden Sie hier.

Sie können das Seminar einfach online buchen.

Falls Sie an diesen Terminen verhindert sind, haben wir bereits einige Termine für das Jahr 2023 für Sie in Planung.


Ihr FromDual Schulungsteam

Taxonomy upgrade extras: galeraschulunggfu20232022seminar

FromDual Performance Monitor for MariaDB/MySQL allows SNMP monitoring

Shinguz - Thu, 2022-06-23 12:03

The newest release of the Performance Monitor for MariaDB and MySQL v2.0.0 (fpmmm) allows you to monitor your MariaDB and MySQL databases via SNMP (Simple Network Management Protocol).

This feature enables you to report your Database Metrics into Enterprise Monitoring solutions from Microsoft, IBM or into Oracle Cloud Control.

In this article we will show you the few simple steps it needs to send the data from your fpmmm Agent to your SNMP Manager.

Check if SNMP Manager can be reached

To make sure fpmmm can send data to the SNMP Manager at all you can test the connection with the following command to send SNMP Notifications to the SNMP Manager:

# COMMUNITY='public' # MANAGER='192.168.56.102' # PORT='162' # TRAP_OID='1.3.6.1.4.1.57800.1.1.2' # OID='1.3.6.1.4.1.57800.1.1.1' # TYPE='c' # VALUE=$(mariadb --user=root --execute="SELECT variable_value FROM information_schema.global_status WHERE variable_name LIKE 'threads_running'\G" | grep variable_value | cut -d' ' -f2) # snmptrap -v 2c -c ${COMMUNITY} ${MANAGER}:${PORT} '' ${TRAP_OID} ${OID} ${TYPE} "${VALUE}"

Then check in the SNMP Manager Logfile if the traps arrive.

Copy fpmmm MIBs to your fpmmm Agent Machine

You can see where your fpmmm MIBs are expected on your database machine (where your fpmmm Agent is located) with the following command:

# net-snmp-config --default-mibdirs ${HOME}/.snmp/mibs:/usr/share/snmp/mibs:/usr/share/snmp/mibs/iana:/usr/share/snmp/mibs/ietf:/usr/share/mibs/site:/usr/share/snmp/mibs:/usr/share/mibs/iana:/usr/share/mibs/ietf:/usr/share/mibs/netsnmp

Copy the fpmmm MIBs as follows (we assume that you work with the same user as your fpmmm Agent works (zabbix or mysql)):

# mkdir -p ${HOME}/.snmp/mibs # cp /opt/fpmmm/tpl/FromDual-fpmmm-MIB.mib ${HOME}/.snmp/mibs

or choose any other location you want to have them.

To check if the FromDual MIBs are recognized correctly run these commands:

# snmptranslate -DFromDual-fpmmm-MIB.mib -m +FromDual-fpmmm-MIB 1.3.6.1.4.1.57800.1.1.1 registered debug token FromDual-fpmmm-MIB.mib, 1 FromDual-fpmmm-MIB::fpmmmLastrun # snmptranslate -On FromDual-fpmmm-MIB::fpmmmLastrun .1.3.6.1.4.1.57800.1.1.1

Do the same for the SNMP Manager according to your installation instructions of your SNMP Manager.

Configure your FromDual Performance Monitor to send SNMP traps

The fpmmm Configuation File (/etc/fpmmm.conf) should contain at least the following lines to make fpmmm sending SNMP traps instead of Zabbix messages:

[default] # SNMP Server SnmpServer = 192.168.56.102 SnmpCommunity = public SnmpTrapPort = 162 OutputFormat = snmp

Do a test run of fpmmm with:

# /opt/fpmmm/bin/fpmmm --config=/etc/fpmmm.conf

Then check again on your SNMP Server machine if the SNMP traps arrive:

snmptrapd: Agent Address: 0.0.0.0 Agent Hostname: Date: 1 - 1 - 4 - 1 - 1 - 1970 Enterprise OID: . Trap Type: Cold Start Trap Sub-Type: 0 Community/Infosec Context: TRAP2, SNMP v2c, community public Uptime: 0 Description: Cold Start PDU Attribute/Value Pair Array:#012DISMAN-EVENT-MIB::sysUpTimeInstance = Timeticks: (1215419) 3:22:34.19#012SNMPv2-MIB::snmpTrapOID.0 = OID: SNMPv2-SMI::enterprises.57800.1.1.2#012SNMPv2-SMI::enterprises.57800.1.1.1 = Counter32: 3 snmptrapd: Agent Address: 0.0.0.0 Agent Hostname: Date: 1 - 1 - 4 - 1 - 1 - 1970 Enterprise OID: . Trap Type: Cold Start Trap Sub-Type: 0 Community/Infosec Context: TRAP2, SNMP v2c, community public Uptime: 0 Description: Cold Start PDU Attribute/Value Pair Array:#012DISMAN-EVENT-MIB::sysUpTimeInstance = Timeticks: (60) 0:00:00.60#012SNMPv2-MIB::snmpTrapOID.0 = OID: SNMPv2-SMI::enterprises.57800.1.1.2#012SNMPv2-SMI::enterprises.57800.2.7.1 = Counter32: 1 snmptrapd: Agent Address: 0.0.0.0 Agent Hostname: Date: 1 - 1 - 4 - 1 - 1 - 1970 Enterprise OID: . Trap Type: Cold Start Trap Sub-Type: 0 Community/Infosec Context: TRAP2, SNMP v2c, community public Uptime: 0 Description: Cold Start PDU Attribute/Value Pair Array:#012DISMAN-EVENT-MIB::sysUpTimeInstance = Timeticks: (60) 0:00:00.60#012SNMPv2-MIB::snmpTrapOID.0 = OID: SNMPv2-SMI::enterprises.57800.1.1.2#012SNMPv2-SMI::enterprises.57800.2.7.2 = Counter32: 151 snmptrapd: Agent Address: 0.0.0.0 Agent Hostname: Date: 1 - 1 - 4 - 1 - 1 - 1970 Enterprise OID: . Trap Type: Cold Start Trap Sub-Type: 0 Community/Infosec Context: TRAP2, SNMP v2c, community public Uptime: 0 Description: Cold Start PDU Attribute/Value Pair Array:#012DISMAN-EVENT-MIB::sysUpTimeInstance = Timeticks: (60) 0:00:00.60#012SNMPv2-MIB::snmpTrapOID.0 = OID: SNMPv2-SMI::enterprises.57800.1.1.2#012SNMPv2-SMI::enterprises.57800.2.7.1 = Counter32: 1 snmptrapd: Agent Address: 0.0.0.0 Agent Hostname: Date: 1 - 1 - 4 - 1 - 1 - 1970 Enterprise OID: . Trap Type: Cold Start Trap Sub-Type: 0 Community/Infosec Context: TRAP2, SNMP v2c, community public Uptime: 0 Description: Cold Start PDU Attribute/Value Pair Array:#012DISMAN-EVENT-MIB::sysUpTimeInstance = Timeticks: (60) 0:00:00.60#012SNMPv2-MIB::snmpTrapOID.0 = OID: SNMPv2-SMI::enterprises.57800.1.1.2#012SNMPv2-SMI::enterprises.57800.2.7.3 = Counter32: 1

This is already all about making fpmmm capable sending SNMP traps.

Sources
Taxonomy upgrade extras: performanceperformance monitoringmonitorfpmmmSNMP

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