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Thank you for the feedback, I have used pacemaker for other purposes previously so am a little familiar with it. It appears that in this scenario pacemaker is being used to manage a floating ip as well as deal with split brain
scenarios. What isn’t clear is how effective master-> master replication is being accomplished. Postgresql streaming replication to the best of my limited knowledge only replicates in one direction, from the active to the standby servers. The issue this presents
to me is that once you failover from the active to the standby (or one of the standby’s depending on how many you have) none of the data written on the standby is replicated back to the formerly active server. Let us say that I have only 2 postgresql servers (absolute minimum number) and I want to patch server A. Ideally, I would use a load balancer (or other failover mechanism like pacemaker) and repoint
the floating ip to server B. Now traffic would “drain” down off server A, and slowly (or rapidly) move to B. During the move some clients would still be writing to A and some clients would be writing to B. Once they have all moved to B, server A would then
be patched. Then the load balancer would be used to repoint the floating ip again back to A, and the process would repeat, with traffic moving back to A. Just like in the first half of the failover some traffic would exist on both hosts as the failover progresses.
Once completed all the traffic would be back on A. In the above scenario, I do not understand how streaming replication would handle the part of the scenario when there are clients writing to A and B. It would seem that something like `pgpool-ii`
or `pgEdge` would be required, but with my limited knowledge it is unclear if or which would be appropriate. Regards Jason
Jason Grammenos | Operations & Infrastructure Analyst Learn new PR tips from our free resources. From: Олег Самойлов <splarv@xxxxx>
For Postgresql HA cluster the most popular solution is streaming replication. There is an option how implement this. Web programmer approach is using haproxy+consul+patrony. The "old schoool" is using Pacemaker, all in one bottle and well
tested. If you interesting how implement in Pacemaker, you may look at my project of testbed that continuously test different HA clusters by random failures. I don't see such for haproxy+consul+patrony. 11.10.2023, 21:02, "Jason Grammenos" <jason.grammenos@xxxxxxxxxxxxx>:
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