Max_allowed_packet

We recently run into some troubles with max_allowed_packet size problems during backups with the FromDual Backup/Recovery Manager and thus I investigated a bit more in the symptoms of such problems.

Read more about: max_allowed_packet.

A general rule for max_allowed_packet size to avoid problems is: All clients and the server should have set the same value for max_allowed_packet size!

I prepared some data for the test which looked as follows:

mysql> SELECT id, LEFT(data, 30), LENGTH(data), ts FROM test; …

1700 - 1749 2050 - 2099

• Error: 2000 (CR_UNKNOWN_ERROR)

  Message: Unknown MySQL error

• Error: 2001 (CR_SOCKET_CREATE_ERROR)

  Message: Can’t create UNIX socket (%d)

  ---

• Error: 2002 (CR_CONNECTION_ERROR) Message: Can’t connect to local MySQL server through socket ‘%s’

  How does the MySQL error message look like?

  shell> mysql --user=root --socket=/tmp/mysql.sock
  ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/tmp/mysql.sock' (2)
  

  What does the MySQL error …