feat: add pprof and prometheus metrics to coder server (#1266)

coderd/httpmw/prometheus.go

@@ -0,0 +1,110 @@
+package httpmw
+
+import (
+	"net/http"
+	"strconv"
+	"time"
+
+	"github.com/go-chi/chi/v5"
+	chimw "github.com/go-chi/chi/v5/middleware"
+
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promauto"
+)
+
+var (
+	requestsProcessed = promauto.NewCounterVec(prometheus.CounterOpts{
+		Namespace: "coderd",
+		Subsystem: "api",
+		Name:      "requests_processed_total",
+		Help:      "The total number of processed API requests",
+	}, []string{"code", "method", "path"})
+	requestsConcurrent = promauto.NewGauge(prometheus.GaugeOpts{
+		Namespace: "coderd",
+		Subsystem: "api",
+		Name:      "concurrent_requests",
+		Help:      "The number of concurrent API requests",
+	})
+	websocketsConcurrent = promauto.NewGauge(prometheus.GaugeOpts{
+		Namespace: "coderd",
+		Subsystem: "api",
+		Name:      "concurrent_websockets",
+		Help:      "The total number of concurrent API websockets",
+	})
+	websocketsDist = promauto.NewHistogramVec(prometheus.HistogramOpts{
+		Namespace: "coderd",
+		Subsystem: "api",
+		Name:      "websocket_durations_ms",
+		Help:      "Websocket duration distribution of requests in milliseconds",
+		Buckets: []float64{
+			durationToFloatMs(01 * time.Millisecond),
+			durationToFloatMs(01 * time.Second),
+			durationToFloatMs(01 * time.Minute),
+			durationToFloatMs(01 * time.Hour),
+			durationToFloatMs(15 * time.Hour),
+			durationToFloatMs(30 * time.Hour),
+		},
+	}, []string{"path"})
+	requestsDist = promauto.NewHistogramVec(prometheus.HistogramOpts{
+		Namespace: "coderd",
+		Subsystem: "api",
+		Name:      "request_latencies_ms",
+		Help:      "Latency distribution of requests in milliseconds",
+		Buckets:   []float64{1, 5, 10, 25, 50, 100, 500, 1000, 5000, 10000, 30000},
+	}, []string{"method", "path"})
+)
+
+func durationToFloatMs(d time.Duration) float64 {
+	return float64(d.Milliseconds())
+}
+
+func Prometheus(next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		var (
+			start  = time.Now()
+			method = r.Method
+			rctx   = chi.RouteContext(r.Context())
+		)
+		sw, ok := w.(chimw.WrapResponseWriter)
+		if !ok {
+			panic("dev error: http.ResponseWriter is not chimw.WrapResponseWriter")
+		}
+
+		var (
+			dist     *prometheus.HistogramVec
+			distOpts []string
+		)
+		// We want to count websockets separately.
+		if isWebsocketUpgrade(r) {
+			websocketsConcurrent.Inc()
+			defer websocketsConcurrent.Dec()
+
+			dist = websocketsDist
+		} else {
+			requestsConcurrent.Inc()
+			defer requestsConcurrent.Dec()
+
+			dist = requestsDist
+			distOpts = []string{method}
+		}
+
+		next.ServeHTTP(w, r)
+
+		path := rctx.RoutePattern()
+		distOpts = append(distOpts, path)
+		statusStr := strconv.Itoa(sw.Status())
+
+		requestsProcessed.WithLabelValues(statusStr, method, path).Inc()
+		dist.WithLabelValues(distOpts...).Observe(float64(time.Since(start)) / 1e6)
+	})
+}
+
+func isWebsocketUpgrade(r *http.Request) bool {
+	vs := r.Header.Values("Upgrade")
+	for _, v := range vs {
+		if v == "websocket" {
+			return true
+		}
+	}
+	return false
+}