add a prometheus /metrics endpoint (std.prometheus)#448
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first phase of observability support. std.prometheus.serve(host, port) runs an
accept loop that answers GET /metrics with the text exposition of every
registered std.metrics series (labels included), and 404 for anything else.
spawn it alongside an app and prometheus scrapes it on its interval:
spawn prometheus.serve("0.0.0.0", 9464)
it reuses what already exists: metrics.snapshot_text() for the body and the
std.net.http request/response helpers over the raw tcp accept primitives, so no
server framework is needed. the endpoint is read-only and pull-based, so serve()
just renders the current snapshot per request; concurrent scrapes are safe
because the metric maps are mutex-guarded.
verified: a unit test on the response (content type + snapshot), a live
self-scrape (spawn serve, GET /metrics over the http client -> 200 with the
labeled counter and gauge present), a new deterministic example, and 86 examples.
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summary
first phase of observability support.
std.prometheus.serve(host, port)runs anaccept loop that answers
GET /metricswith the text exposition of everyregistered
std.metricsseries (labels included), 404 otherwise. spawn italongside an app and prometheus scrapes it on its interval:
it reuses what exists —
metrics.snapshot_text()for the body, thestd.net.httprequest/response helpers over the raw
tcp_acceptprimitives — so no serverframework is needed. read-only and pull-based;
serve()renders the currentsnapshot per request, and concurrent scrapes are safe (the metric maps are
mutex-guarded).
part of the observability sprint (prerequisites #441/#445/#446 already landed).
next:
std.trace+ OTLP export.what was tested
metrics_response()(prometheus content type + snapshot present)serve, GET/metricsover the http client → 200with the labeled counter and gauge in the body
examples/prometheus_metrics.pith; 86 examplespure-additive stdlib; no compiler change, no bootstrap seed refresh.