Serve /metrics from a registry of its own (closes #227)

A second metrics-enabled router in one process panicked on a duplicate collector registration, because every collector registered on Prometheus's global default registry. metrics.NewRegistry now builds one registry with the Go runtime and process collectors; fx provides it and the delivery metric set built on it. The middleware builds its HTTP recorder once on that registry (NewForTest on a fresh one), the engine and handlers take the metric set from fx, and nothing registers on the global default any more. /metrics is served from the new registry with the same series names, labels and auth. A test builds two metrics-enabled routers in one process. Model: opus-5-5
2026-10-02 09:06:20 +02:00
parent cb7bafab17
commit eb4c4cc849
17 changed files with 194 additions and 64 deletions
@@ -35,9 +35,8 @@ const (
 )

 // mIsolate gives the setup's engine a metric set registered on a
-// private registry. The process-wide collectors are moved by every
-// other delivery test running in parallel, so exact assertions are
-// only possible against a registry this test owns.
+// registry this test holds, so its exact assertions can gather from
+// it.
 func mIsolate(
 	t *testing.T, s iSetup,
 ) *prometheus.Registry {