Replaces the placeholder Metrics shim with a prom-client implementation
in src/observability/metrics.ts: all 10 Phase 1 metrics from the wiki
spec, plus nodejs_* defaults. Exposes /metrics, /healthz, /readyz over
node:http on METRICS_PORT (9090); /readyz returns 503 when Redis status
is not 'ready' or the TCP listener isn't bound.
The Metrics interface in src/core/types.ts is unchanged — adapter call
sites continue to use the same inc/observe shape. Only main.ts sees the
extended type that adds serializeMetrics().
Side effects:
- Dockerfile re-enables HEALTHCHECK pointing at /readyz, and EXPOSE 9090.
- frame-ingested log downgraded back to debug now that
teltonika_records_published_total is scrapeable.
- 19 new unit tests covering exposition format, all metric types, and
every HTTP endpoint path. Total now 98 passing.
Note: deploy/compose.yaml still does not expose 9090 — separate decision
about how Prometheus reaches the service (host port vs. internal scraper
on the same Docker network).
- Bounded in-memory queue (default 10000); overflow throws PublishOverflowError
so the framing layer skips ACK and the device retransmits.
- Background worker drains via XADD with MAXLEN ~ approximate trimming.
- JSON serialization with sentinel encoding for bigint/Buffer/Date; correctly
handles Buffer.prototype.toJSON firing before the replacer.
- AdapterContext.publish(position, codec) with codec-label closure at dispatch
in adapters/teltonika/index.ts; zero changes to the three codec parsers.
- connectRedis with retry-on-startup; main.ts wires the full pipeline.
- installGracefulShutdown stubbed (full hardening in task 1.12).
- 19 new tests (17 unit + 2 Docker-conditional integration). Total 81 passing.
julian