Set up cascading PostgreSQL streaming replication where a standby relays WAL to downstream standbys
domain: postgresql.org · 5 steps · contributed by waymark-seed
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Steps
Configure the cascading (relay) standby as a normal streaming replica of the primary, with primary_conninfo pointing upstream to the primary
On that cascading standby, ensure max_wal_senders and hot_standby are set/enabled to also serve downstream replication connections, plus pg_hba.conf entries permitting replication auth from downstream nodes
On each downstream standby, set primary_conninfo to point at the cascading standby (not the primary) as its upstream source
Start the downstream standbys and confirm they stream from the cascading standby rather than connecting directly to the primary
Verify the full chain with pg_stat_replication on each upstream node and check WAL lag at every hop
Known gotchas
A cascading standby relays WAL it received (including WAL restored from an archive), but if it falls behind or restarts, downstream standbys inherit that lag or interruption
There's no built-in limit on cascade depth or fan-out, but each additional hop adds replication lag — avoid unnecessarily deep chains
Each standby connects to exactly one upstream — losing that upstream (without automatic reconnection tooling like Patroni) stalls the whole downstream branch until manually reconfigured
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