[saisrirampur]

Great question! We have retry logic in place to handle Postgres restarts. If the failure occurs in-place, you should be fine as the slot will persist. If Postgres fails over to the standby, PeerDB will wait until the slot is created. We did consider automatically creating the slot if it doesn't exist on retries, but ensuring data reliability (creating the slot right after failover without data being ingested) is tricky. So, as of now, we leave it to the user.

[take-five]

Thanks! I'd say, this is a very complicated problem left to be solved by user. Debezium also does not solve the problem it, and from DBA point of view it is a blocker for adoption. Would be nice to have some solution that would ensure that logical replication slot persists through failover.

[gunnarmorling]

Things got finally a bit easier with Postgres 16, which allows you to create replication slots on stand-by servers. It still requires manual intervention to make sure they don't fall too far behind their primary counterpart and to do the failover, but it's not too terrible either and it's guaranteed that failover can happen without missing any events. I've described the approach here: https://www.decodable.co/blog/logical-replication-from-postg.... Postgres 17 should make this even simpler.

[saisrirampur]

Quite a bit of work is going on to support failover slots in upstream - https://github.com/search?q=repo%3Apostgres%2Fpostgres+failo... From what I understood it could get into Postgres 17 (released later this year) if there are no big issues. :)