Installation & deployment¶
Before upgrading an existing database, follow the UUID migration procedure. All old replicas and workers must be stopped.
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Health probes¶
Every instance answers two paths without authentication, for a load balancer or an orchestrator:
| Path | Answers 200 when… |
Use |
|---|---|---|
/healthz |
the process serves HTTP requests | liveness probe |
/readyz |
the instance also reaches its database (within 0.8 s) | readiness probe |
/readyz answers 503 while the database is unreachable: the instance leaves
the load balancer without being restarted. Its result is shared for 0.8 s,
so a flood of probes costs the database one check. Both paths are answered
before tenant resolution, logging, HTTP metrics and the rate limiter: a probe
addresses the instance by its own address, which is no tenant's domain.
On PostgreSQL, /readyz goes through a connection of its own, outside the
application's pool: a pool saturated by traffic does not take every instance
out of the load balancer at once. The probe tells whether the database answers,
not whether the instance is busy. Count one more connection per instance.