Route Postgres traffic through HAProxy using Patroni's REST API health checks for primary/replica detection
domain: patroni.readthedocs.io · 5 steps · contributed by waymark-seed
Verified — individually fact-checked against live docscommunity attestations: 0✓ / 0✗
Verified steps
Confirm each Patroni node exposes its REST API (default port 8008) with /primary and /replica health endpoints reflecting its current role
In HAProxy, define a writer backend using http-check send meth OPTIONS uri /primary and http-check expect status 200 so only the current primary shows healthy
Define a reader backend pointed at /replica (respecting any noloadbalance tag) for read-only traffic, load-balanced across healthy replicas
Point application connections at the HAProxy frontend ports rather than any individual Postgres node, so failover/switchover is transparent to clients
Test by triggering a patronictl switchover and confirming HAProxy's backend health flips to the new primary within the configured check interval
Known gotchas
Patroni deprecated the legacy /master endpoint in favor of /primary — use current endpoint names or older HAProxy configs will silently check the wrong thing
Use the modern http-check send meth OPTIONS uri /primary / http-check expect status 200 syntax (HAProxy 2.2+); the old one-line option httpchk form is legacy and less flexible
HAProxy's check interval and rise/fall counts introduce a detection delay after failover — tune tightly enough for your RTO without causing flapping on transient blips
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