Multi-Tenant

Table of contents

• Overview
• Preparation of the shards (MariaDB database instances)
  • Create test data
  • Creating roles and users
  • MaxScale Monitor User
  • MaxScale Admin User
  • Create application role and accounts
  • Proxy protocol
• MaxScale SchemaRouter configuration
• Starting and stopping the MaxScale Load Balancer
• Application tests
  • Simple application tests
  • New command show shards
  • More general test
  • Less simple tests
  • More complex application tests
  • Cross-shard tests
• Operation of a MaxScale sharding system …

As already mentioned earlier, we roughly have a hand full of customers which are playing with the though of sharding solutions. They typically have many different customers (clients, tenants) and the number of customers becomes so huge (thousands to millions) that one machine cannot cope with the load any more.

So splitting the load by customers to different machines makes sense. This is quite easy when customers are separated per schema. In the good old times of Open Source our customers have implemented …

Once in a year or so we get a request of a customer about MariaDB/MySQL sharding solutions. So here we have a list of sharding solutions we are currently aware of:

• MySQL Fabric: A Brief Introduction to MySQL Fabric This product is discontinued by MySQL in the meanwhile!
• Spider Storage Engine for MariaDB: Spider Storage Engine Overview
• MariaDB MaxScale: Simple Sharding with Two Servers and Schema Router
• ProxySQL: Sharding in ProxySQL
• PingCap TiDB (Titan DB): Release Candidate der verteilten Datenbank TiDB …

The number of table definitions (SHOW CREATE TABLE<br>G) that can be stored in the table definition cache (table_definition_cache). If you have a large number of tables (
> 400) in your database instance, you should consider a larger table definition cache to increase your database throughput and decrease your query latency.
The command SELECT COUNT(*) FROM information_schema.tables; shows you how many tables and thus table definitions you have. The global status Open_table_definitions is the …

The Table Open Cache (table_open_cache or old name table_cache) is a cache to store file handles for all threads. The actual value of cache entries can be seen with the global status of open tables (Open_tables).
Increasing table_open_cache increases the number of file descriptors (open_files_limit) that MySQL requires.
You can check whether you need to increase the Table Open Cache by checking Open_tables and Opened_tables. If the value of Opened_tables is large and you do not use FLUSH TABLES often (which …

Introduction

Recently a customer claimed that his queries were slow some times and sometimes they were fast.

First idea: Flipping query execution plan caused by InnoDB could be skipped because it affected mainly MyISAM tables.

Second idea: Caching effects by either the file system cache caching MyISAM data or the MyISAM key buffer caching MyISAM indexes were examined: File system cache was huge and MyISAM key buffer was only used up to 25%.

I was a bit puzzled…

Then we checked the table_open_cache …

If you ask around about shared hosting setups with MySQL everybody is frightened. In fact it looks like shared hosting is one of the most difficult setups you can get.

The number of users is big, the number of tables huge and the load pattern is completely unpredictable and the queries often very, let us say: non-optimal.

Here one of the DBA wisdoms come into play: Controlling developers is like herding cats.

If you talk to the Shared MySQL Hoster they confirm that this setups are very demanding!

Why is …