Auth for metrics, removed unwanted metrics and fixed tests.

api/api.go

@@ -110,13 +110,14 @@ func (h *Handler) handleHealth(w http.ResponseWriter, r *http.Request) {
 }
 
 func (h *Handler) handleMetrics(w http.ResponseWriter, r *http.Request) {
-	payload := metrics.Default.RenderPrometheus()
 	w.Header().Set("Content-Type", "text/plain; version=0.0.4; charset=utf-8")
-	w.Header().Set("Content-Length", strconv.Itoa(len(payload)))
-	w.WriteHeader(http.StatusOK)
 	if r.Method == http.MethodHead {
+		w.WriteHeader(http.StatusOK)
 		return
 	}
+	payload := metrics.Default.RenderPrometheus()
+	w.Header().Set("Content-Length", strconv.Itoa(len(payload)))
+	w.WriteHeader(http.StatusOK)
 	_, _ = w.Write([]byte(payload))
 }
 
@@ -645,7 +646,6 @@ func newLimitedListener(inner net.Listener, maxConns int) net.Listener {
 		return inner
 	}
 	metrics.Default.SetConnectionPoolMax(maxConns)
-	metrics.Default.SetWorkerPoolSize(maxConns)
 	return &limitedListener{
 		Listener: inner,
 		slots:    make(chan struct{}, maxConns),

auth/middleware.go

@@ -25,7 +25,7 @@ func Middleware(
 				return
 			}
 
-			if r.URL.Path == "/healthz" || r.URL.Path == "/metrics" {
+			if r.URL.Path == "/healthz" {
 				metrics.Default.ObserveAuth("bypass", "none", "public_endpoint")
 				next.ServeHTTP(w, r.WithContext(WithRequestContext(r.Context(), authCtx)))
 				return

logging/logging.go

@@ -90,10 +90,8 @@ func HTTPMiddleware(logger *slog.Logger, cfg Config) func(http.Handler) http.Han
 			ww := middleware.NewWrapResponseWriter(w, r.ProtoMajor)
 			op := metricOperationLabel(r)
 			metrics.Default.IncHTTPInFlightOp(op)
-			metrics.Default.IncWorkerPoolActive()
 			defer func() {
 				metrics.Default.DecHTTPInFlightOp(op)
-				metrics.Default.DecWorkerPoolActive()
 			}()
 			requestID := middleware.GetReqID(r.Context())
 			if requestID != "" {

metrics/metrics.go

@@ -75,8 +75,6 @@ type Registry struct {
 	connectionPoolWaits  atomic.Uint64
 
 	requestQueueLength atomic.Int64
-	workerPoolActive   atomic.Int64
-	workerPoolSize     atomic.Int64
 
 	mu sync.Mutex
 
@@ -364,21 +362,6 @@ func (r *Registry) DecRequestQueueLength() {
 	r.requestQueueLength.Add(-1)
 }
 
-func (r *Registry) SetWorkerPoolSize(size int) {
-	if size < 0 {
-		size = 0
-	}
-	r.workerPoolSize.Store(int64(size))
-}
-
-func (r *Registry) IncWorkerPoolActive() {
-	r.workerPoolActive.Add(1)
-}
-
-func (r *Registry) DecWorkerPoolActive() {
-	r.workerPoolActive.Add(-1)
-}
-
 func (r *Registry) ObserveLockWait(lockName string, d time.Duration) {
 	lockName = strings.TrimSpace(lockName)
 	if lockName == "" {
@@ -520,10 +503,7 @@ func (r *Registry) RenderPrometheus() string {
 	connectionMax := float64(r.connectionPoolMax.Load())
 	connectionWaits := r.connectionPoolWaits.Load()
 	queueLength := float64(r.requestQueueLength.Load())
-	workerActive := float64(r.workerPoolActive.Load())
-	workerSize := float64(r.workerPoolSize.Load())
 
-	openFDs, hasOpenFDs := readOpenFDs()
 	resident, hasResident := readResidentMemoryBytes()
 	cpuSeconds, hasCPU := readProcessCPUSeconds()
 
@@ -555,8 +535,6 @@ func (r *Registry) RenderPrometheus() string {
 	writeCounter(&b, "fs_connection_pool_waits_total", "Number of waits due to pool saturation.", connectionWaits)
 
 	writeGauge(&b, "fs_request_queue_length", "Requests waiting for an execution slot.", queueLength)
-	writeGauge(&b, "fs_worker_pool_active", "Active workers.", workerActive)
-	writeGauge(&b, "fs_worker_pool_size", "Configured worker pool size.", workerSize)
 
 	writeHistogramVecKV(&b, "fs_lock_wait_seconds", "Time spent waiting for locks.", lockWait, []string{"lock_name"})
 	writeHistogramVecKV(&b, "fs_lock_hold_seconds", "Time locks were held.", lockHold, []string{"lock_name"})
@@ -594,10 +572,6 @@ func (r *Registry) RenderPrometheus() string {
 	if hasResident {
 		writeGauge(&b, "process_resident_memory_bytes", "Resident memory size in bytes.", resident)
 	}
-	if hasOpenFDs {
-		writeGauge(&b, "process_open_fds", "Number of open file descriptors.", openFDs)
-		writeGauge(&b, "fs_open_fds", "Number of open file descriptors.", openFDs)
-	}
 
 	return b.String()
 }
@@ -732,8 +706,16 @@ func writeHistogramWithLabelsMap(b *strings.Builder, name string, labels map[str
 		}
 		fmt.Fprintf(b, "%s_bucket{%s} %d\n", name, labelsToString(bucketLabels), cumulative)
 	}
-	fmt.Fprintf(b, "%s_sum{%s} %.9f\n", name, labelsToString(labels), s.sum)
-	fmt.Fprintf(b, "%s_count{%s} %d\n", name, labelsToString(labels), s.count)
+	labelsSuffix := formatLabelsSuffix(labels)
+	fmt.Fprintf(b, "%s_sum%s %.9f\n", name, labelsSuffix, s.sum)
+	fmt.Fprintf(b, "%s_count%s %d\n", name, labelsSuffix, s.count)
+}
+
+func formatLabelsSuffix(labels map[string]string) string {
+	if len(labels) == 0 {
+		return ""
+	}
+	return "{" + labelsToString(labels) + "}"
 }
 
 func formatLabels(keys, values []string) string {
@@ -786,14 +768,6 @@ func escapeLabelValue(value string) string {
 	return value
 }
 
-func readOpenFDs() (float64, bool) {
-	entries, err := os.ReadDir("/proc/self/fd")
-	if err != nil {
-		return 0, false
-	}
-	return float64(len(entries)), true
-}
-
 func readResidentMemoryBytes() (float64, bool) {
 	data, err := os.ReadFile("/proc/self/statm")
 	if err != nil {

metrics/metrics_test.go

@@ -0,0 +1,26 @@
+package metrics
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestRenderPrometheusHistogramNoEmptyLabelSet(t *testing.T) {
+	reg := NewRegistry()
+	reg.ObserveBatchSize(3)
+	reg.ObserveGC(0, 0, 0, 0, true)
+
+	out := reg.RenderPrometheus()
+	if strings.Contains(out, "fs_batch_size_histogram_sum{}") {
+		t.Fatalf("unexpected empty label set for batch sum metric")
+	}
+	if strings.Contains(out, "fs_batch_size_histogram_count{}") {
+		t.Fatalf("unexpected empty label set for batch count metric")
+	}
+	if strings.Contains(out, "fs_gc_duration_seconds_sum{}") {
+		t.Fatalf("unexpected empty label set for gc sum metric")
+	}
+	if strings.Contains(out, "fs_gc_duration_seconds_count{}") {
+		t.Fatalf("unexpected empty label set for gc count metric")
+	}
+}