Hi, I'm working with *logical replication* in a PostgreSQL 17 setup, and I'm exploring the new synchronized_standby_slots parameter to make replication slots failover safe in a highly available environment using physical standby nodes managed by Patroni.
While testing this feature, I encountered a blocking behavior, when a *standby is listed in synchronized_standby_slots* and that standby goes offline, *logical replication on the primary stops progressing*. From what I understand, the primary node waits for the standby to acknowledge received wal records, effectively stalling WAL decoding for the logical slot. I noticed that the failover slot on the standby continue to be synced. This raises several questions about the *tradeoffs and implications* of using this feature: - What are the *risks or limitations* if synchronized_standby_slots is *left empty* (the default)? Is there a risk of data loss or inconsistency for logical subscribers in such cases? - Is it expected behavior that *any failure of a standby listed in synchronized_standby_slots stalls logical decoding* on the primary? If so, are there any ways to *avoid blocking* WAL decoding while still having slot synchronization? - Patroni is managing FO slots better than native Postgres impletmentation? Thanks for helping on those points Regards, Fabrice
