[Pacemaker] MySQL, Percona replication manager - split brain

[Ken Gaillot]

On 10/25/2014 03:32 PM, Andrew wrote:
> 2) How to resolve split brain state? Is it enough just to wait for
> failure, then - restart mysql by hand and clean row with dup index in
> slave db, and then run resource again? Or there is some automation for
> such cases?

Regarding mysql cleanup, it is usually NOT sufficient to fix the one row 
with the duplicate key. The duplicate key is a symptom of prior data 
inconsistency, and if that isn't cleaned up, at best you'll have 
inconsistent data in a few rows, and at worst, replication will keep 
breaking at seemingly random times.

You can manually compare the rows immediately prior to the duplicate ID 
value to figure out where it started, or use a special-purpose tool for 
checking consistency, such as pt-table-checksum from the Percona toolkit.

-- Ken Gaillot <kjgaillo at gleim.com>
Network Operations Center, Gleim Publications