metrics: Prometheus text exposition for /metrics

/metrics was Prometheus-ish name/value text with a custom banner and text/plain Content-Type, so strict scrapers could fail. Emit Prometheus text 0.0.4 (# HELP, # TYPE, counter|gauge) with stable metric names, and set Content-Type to text/plain; version=0.0.4; charset=utf-8.
2026-09-08 19:53:58 +00:00
parent 0db9943436
commit dd72668c2d
7 changed files with 200 additions and 29 deletions
@@ -109,6 +109,8 @@ Heartbeat also returns `X-SteamCache-Disk-Tier: pending|ready|disabled` (`disabl

 These are the cache process's own `/metrics` and `/lancache-heartbeat` endpoints. There is no separate metrics daemon.

+`/metrics` is Prometheus text exposition format 0.0.4 (`Content-Type: text/plain; version=0.0.4; charset=utf-8`) so Prometheus and compatible scrapers can pull it. Metric names in the table above are unchanged; each series is preceded by `# HELP` and `# TYPE`.
+
 If you changed `listen_address`, point curl at that host:port instead. For a full SteamPrefill validation workflow (small caches, coalescing, GC), see [Validating Full Functionality](#validating-full-functionality-with-external-tools).

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