Why Uber dropped PostgreSQL

Posted Aug 5, 2016 15:11 UTC (Fri) by paulj (subscriber, #341)
In reply to: Why Uber dropped PostgreSQL by brong
Parent article: Why Uber dropped PostgreSQL

Well, we're talking about bugs. Anything is possible, right?

With the low-level binary log replication, bugs that lead to corruption can replicate.

With the logical level replication, bugs that lead to logical level corruption can also cause inconsistent state. E.g., an update doesn't get applied to slaves because it isn't accepted, which could affect application consistency. Bugs at the binary log level may not replicate of themselves, but could cause a logical level replication to fail to replicate and cause inconsistent state.

Isn't it the case that the logical layer replication system has _two_ layers at which bugs can strike and cause significant problems? You now have two layers that need to be robust? And bugs in the lower layer can still take down the upper layer?

Why Uber dropped PostgreSQL

Posted Aug 5, 2016 21:58 UTC (Fri) by brong (guest, #87268) [Link]

If the response to a logical update failing to apply is rejecting the update, then you know that your replication is broken, and you haven't lost anything except the most recent changes - and you can skip that update and apply something manually to fix it while you fail over to a replica and bring it as close to up-to-date as possible.

If your low level data structures are corrupted - better have a good fsck and/or good backups, because you have have no replica with consistent state any more.