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I have a Master-Master cluster with 2 Percona 5.5.30 servers. (Lets name them 1 & 2) The OS is FreeBSD 9.1

I have an issue that server 2 is not processing the relay log fast enough. I know that for sure, because when i create a new table on server 1, and i immidiatly check the relay-log on server 2, i see the CREATE command there, but the table is not being created for another 5-15 minutes or so.

It looks like the thread that is supposed to executing the relay log is halting itself every once in a while, showing NULL in its state when executing SHOW PROCESSLIST;

What can be the reason for that?



(I don't know how to paste SQL here...)

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The next time this happens, please post the output of SHOW PROCESSLIST;. If the processlist is too long, then run SELECT * FROM information_schema.processlist WHERE user='system user'\G – RolandoMySQLDBA Jun 13 '13 at 10:29
Added to post.. – shaharmor Jun 13 '13 at 15:40

This is quite common. A slave only has a single IO thread (the slave I/o thread) whereas a master is typically executing multiple queries in parallel. You should look at your disk I/O usage (like with iostat) to determine if you're bottle necked there or at the CPU (single thread can use only one core).

The 5.6 series of MySQL can use a separate thread for each schema, which may help.

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So there is nothing i can do right now? – shaharmor Jun 13 '13 at 19:33

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