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

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

    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

    • A is slave of B B is slave of A

    • C is slave of A D is slave of B

    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.