Files
reverse-proxy/docs/architecture/decisions/022-health-check-scope.md
glm-5.1 fe1ae6c05e Resolve all open questions, remove /health from main listener (ADR-022)
Resolve OQ-08 through OQ-12 after reviewing implementation findings:

- OQ-08: Remove /health route from the main HTTPS listener entirely.
  Health checking belongs on port 9900 and admin socket only, not on
  the public-facing proxy. This eliminates upstream collision problems
  and special-case routing logic. (ADR-022)

- OQ-09: Not an architectural unknown — ADR-015 already decided on a
  separate connect timeout. The implementation gap is a known issue.

- OQ-10: Not an open question — acme_contact is already specified as
  required in config.md. The empty contact list is bug C2.

- OQ-11: Hardcoded is_https=true is correct for a TLS-terminating
  proxy. HTTP listener redirects, doesn't proxy. Just needs a comment.

- OQ-12: Access logging is already specified as mandatory/always-on in
  operations.md. Missing log_request! calls are bug W13.

Updated docs: proxy.md, operations.md, overview.md, config.md,
open-questions.md, README.md, ADR-013. Created ADR-022.
2026-06-12 03:39:52 +00:00

2.2 KiB

ADR-022: Health Check Scope — Local Port and Admin Socket Only

Status

Accepted

Context

The implementation served a GET /health route on the main HTTPS listener that returned 200 OK regardless of the Host header. This route was evaluated before host-based routing, meaning any upstream application using /health for its own health checks would have those requests silently intercepted by the proxy and never reach the upstream (implementation review finding W5).

The architecture already specified a separate local health check port (9900, bound to 127.0.0.1 only) via ADR-013. The question was whether to keep the main-listener /health route alongside the dedicated port (and possibly make the path configurable), or to remove it entirely.

Decision

The main HTTPS listener does not serve a /health route. Health checking is handled exclusively by:

  1. Local health check port (default: 9900, bound to 127.0.0.1) — serves GET /health → 200 OK. This is the primary health check mechanism for container orchestration, load balancers, and monitoring systems.
  2. Admin socket (status command) — returns process information including uptime and site count.

The /health route is removed from the main listener entirely. No configurable path is needed because the route simply does not exist on the public listener.

Consequences

Positive:

  • No collision with upstream applications that use /health for their own health checks
  • The main listener's routing logic is simpler — all requests go through host-based routing, no special cases
  • Clear separation of concerns: the main listener proxies, the local port answers health checks
  • No configurable path needed — the problem disappears entirely

Negative:

  • External monitoring that needs to verify TLS is working must connect to the HTTPS port directly and check for a successful TLS handshake or a 404 response, rather than getting a 200 from /health. This is a minor inconvenience — any successful TLS response (even 404) confirms the proxy is serving TLS correctly.

References

  • ADR-013: Health check on separate local port
  • OQ-08: Resolved by this ADR
  • Implementation review finding W5 (hardcoded /health path)