glm-5.1
fecc385d75
- ADR-020: Document defense-in-depth rationale for running in a minimal Docker container (memory-safe language + container isolation), flexible upstream addressing (Docker DNS, loopback, LAN, tunnel endpoints), file-primary logging for fail2ban, and volume mount strategy - ADR-016: Add allow_wildcard_bind override for container deployments where 0.0.0.0 is correct inside the container network namespace - operations.md: Add container deployment section with Docker Compose example, networking table, volume mounts, and health check integration; flip logging to file-primary for fail2ban reliability; note systemd as alternative to container deployment - config.md: Restructure logging fields into nested LoggingConfig (matching TOML [logging] section), add allow_wildcard_bind, shutdown_timeout_secs, and log_file_path fields; clarify upstream addressing supports Docker DNS and tunnel endpoints; update validation rule for 0.0.0.0 override - overview.md: Update architecture diagram for container model with Docker networking and volume mounts; add ADR-020 reference - proxy.md: Clarify X-Forwarded-Proto is determined by listener port, not hardcoded 80/443 - ADR-013: Fix health_check_port default contradiction (default is 9900, not 0/disabled as previously stated)
70 lines
2.6 KiB
Markdown
70 lines
2.6 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. Currently the design places it on the main HTTPS
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listener, which means:
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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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Three options were considered (see OQ-03):
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1. **Main HTTPS listener only**: Simplest, but TLS config errors make health
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checks unreachable
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2. **Separate unencrypted port on localhost**: Simple, works with standard
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monitoring tools, but health checks bypass TLS
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3. **Admin port with its own listener**: Most flexible but adds complexity
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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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separate health check listener, and `/health` remains available on the main
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HTTPS listener as a fallback.
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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` keeps the main HTTPS `/health` endpoint
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available for cases where a separate port isn't needed
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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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- Two health check endpoints exist when the separate port is enabled (the
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local one and the HTTPS one) — monitoring should prefer the local one
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## References
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- [operations.md](../operations.md)
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- OQ-03 (now resolved) |