Two faults compounded into one symptom: with the database unreachable, every
route on the service returned 502 - including /docs, which never touches it.
_connect() passed no connect_timeout. A host that DROPS packets rather than
refusing them, which is what a firewall or a wrong DB_HOST looks like, blocked
until the OS gave up - roughly 130 seconds on Linux. Every caller inherited
that, /api/health included. Now bounded by DB_CONNECT_TIMEOUT_SECONDS,
defaulting to 5. Measured against an unroutable host: /api/health went from
hanging past 25s to answering 200 in 5.07s.
The container healthcheck then probed /api/health, so that hang timed out the
check, the container was marked unhealthy, and the platform stopped routing to
it. That is the part that turned a degraded dependency into a total outage, and
it was introduced with the healthcheck itself.
A healthcheck is a LIVENESS question, because the platform's answer to "no" is
to take the container out of service. It may only ask whether the process is
still serving HTTP. /api/health is a READINESS report - it dials Postgres and
Ollama to say whether they are reachable, and coupling the container's
existence to its dependencies is what made a running API unreachable. It now
probes "/", which is served from memory and does no I/O, so it can fail only if
the app really is gone.
Verified with an unroutable DB host: /, /docs and /openapi.json all answer 200,
and the healthcheck exits 0. With the app stopped it still exits 1.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
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