Comments on: How to sync tables in master-master MySQL replication

By: Xaprb

Xaprb — Sat, 09 Jan 2010 16:43:38 +0000

It is not quite a million dollar question, but it’s something we get asked to do a lot at Percona, and it tends to be very tedious and time consuming, hence it can easily be a thousand dollar question. There is no easy recipe: you have to find the writes and understand what their purpose was, and then figure out whether to keep them, merge conflicts, throw them away, etc. It all depends on how much the data matters to the client, too. A lot of times we give a preliminary check and then go back to the client, who tells us it’s not worth the money and we just pick one server as authoritative.

By: Matt

Matt — Sat, 09 Jan 2010 11:17:20 +0000

Thanks Xaprb, so how do you evaluate the writes is the million dollar question?
Cheers

By: Xaprb

Xaprb — Sat, 09 Jan 2010 01:12:48 +0000

You evaluate the changes to see if they conflict. There is no easy answer to this problem. It is equivalent to permitting writes on both masters and the results can be anything from a non-event to utter chaos.

By: Matt

Matt — Fri, 08 Jan 2010 19:43:59 +0000

Great help thanks..

in the case of a master to master relationship where the backup master has made an insert while master1 is offline.

When master1 comes back online how can we tell which is the most up to date master to sync from?

Cheers
Mat

By: Xaprb

Xaprb — Mon, 02 Nov 2009 19:51:30 +0000

I think that is best to do manually :-(