Use of pt-table-checksum in master-master environments

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1

This topic follows this question on Launchpad

The original question was:
I would like to know if it is safe (from the replication point of view) to run pt-table-checksum toolkit in environments with a master-master MySQL configuration with slaves like this one:

A == B| |C D

Masters:
[LIST]
[] A is slave of B B is slave of A
[/LIST]
Slaves:
[LIST]
[] C is slave of A D is slave of B
[/LIST]
The documentation of the pt-table-checksum do not discuss about such a configuration, unlike the pt-table-sync documentation for example.

In addition to the safety of the tool, I would like also to know if running pt-table-checksum on server A, automatically make the checksums on all the other servers.

The last question was:

I agree with your reply (that of Baron), just wondering why are you referring to a “passive master”.

The configuration I have explained is an active-active master-master replication where both A and B are active masters. The same arguments can be applied also in this case?

Thank you for your attention.

2

One of the cardinal rules of MySQL replication is that you should never write to more than one server. Based on that, you should have an active/passive master/master configuration, and you should run this tool on the active master, not the passive master, because the writes should all go to one server.

3

Obviously I agree with the rule, in this case both servers are active for different projects/schema in order to distribute the load and avoid to have a single server heavy loaded and the other one in standby.
So applying your suggestion to our structure leads to run the pt-table-checksum on one schema at a time on the active master for that schema/project.

Thanks for you clarification.