MySQL replication is not running although mysql says it is

Question

I have two servers configured in a master-master pair using MMM. I recently had an issue where the passive master received a replication error (got a packet bigger than max_allowed_packet) but the slave IO and SQL threads continued running. And seconds_behind_master was still showing as 0 even though the slave was not executing new statements.

I thought this type of error would cause replication to stop (it's done this in the past). Instead replication kept running and our monitors didn't notice the problem. Also the replication errors continually showed up in the mysql error log, instead of "Last_Error" in "show slave status".

We are running version 5.0.33.

Any ideas what happened here? thanks!

Answer 1

For the max allowed packet size, it sounds like your two DBs are not configured identically. At least the network protocol stuff should be identical.

Did you try show slave status on both machines?

Quiet failure is a terrible situation. I wonder what records did not make it. Do you have a way of finding out?

Are you getting periodic errors in the error log or a flood of identical errors? Is the sequence number incrementing on the passive master?

Jacob