glm-5.1
fe1ae6c05e
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.
72 lines
2.9 KiB
Markdown
72 lines
2.9 KiB
Markdown
# ADR-013: Health Check on Separate Local Port
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## Status
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Accepted
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## Context
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The health check endpoint (`/health`) needs to be accessible for monitoring
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without requiring TLS. Serving it on the main HTTPS listener would mean:
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1. TLS handshake must succeed for the health check to respond
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2. External monitoring tools need to handle TLS
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3. A TLS configuration error would make the health check unreachable, creating
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a false-negative monitoring signal
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4. It creates collision with upstream applications that use `/health` for their
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own health checks (see ADR-022)
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Three options were considered (see OQ-03):
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1. **Separate unencrypted port on localhost (chosen)**: Simple, works with
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standard monitoring tools, health checks work even when TLS is misconfigured
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2. **Main HTTPS listener only**: Would require TLS for health checks, creating
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a circular dependency — TLS config errors would make health checks unreachable
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3. **Admin port with its own listener**: Most flexible but adds complexity
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beyond what's needed for a simple health check
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## Decision
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Add a configurable health check port that binds to `127.0.0.1` only (localhost),
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serving `/health` over plain HTTP. This is a separate listener from the main
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HTTP and HTTPS listeners.
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The port is configurable via `health_check_port` in StaticConfig. The default
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value is `9900` (enabled, localhost only). Setting it to `0` disables the
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health check listener entirely — there is no `/health` route on the main HTTPS
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listener (see ADR-022).
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## Rationale
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- A local-only health check port is the standard pattern for reverse proxies
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and service meshes (envoy, haproxy, k8s health probes all use this pattern)
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- Health checks should work even when TLS is misconfigured — that's the whole
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point of monitoring
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- Binding to `127.0.0.1` only means the health check is not exposed to the
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internet — only local monitoring tools (systemd, scripts, load balancers on
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the same host) can reach it
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- Configurable port allows different deployment scenarios (some monitoring runs
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on different ports)
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- Disabling via `health_check_port = 0` removes the health check entirely —
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the admin socket's `status` command remains available as an alternative
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health/status mechanism
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- When this project is folded into alknet, the health check will use alknet's
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existing patterns, making the separate port unnecessary in that context
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## Consequences
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**Positive:**
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- Health checks work even when TLS is misconfigured
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- Standard pattern that monitoring tools expect
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- Not exposed to the internet (localhost only)
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- Configurable — can be disabled if not needed
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- systemd can use it for `NotifyAccess` readiness checks
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**Negative:**
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- Additional listener to manage (minimal complexity)
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## References
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- [operations.md](../operations.md)
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- [ADR-022](022-health-check-scope.md) — Health check scope (no `/health` on main listener)
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- OQ-03 (now resolved) |