Add metrics for HTTP calls

cmd/syncthing/gui.go

@@ -25,6 +25,7 @@ import (
 	"strings"
 	"time"
 
+	"github.com/rcrowley/go-metrics"
 	"github.com/syncthing/syncthing/lib/auto"
 	"github.com/syncthing/syncthing/lib/config"
 	"github.com/syncthing/syncthing/lib/db"
@@ -180,10 +181,11 @@ func (s *apiSvc) Serve() {
 
 	// Debug endpoints, not for general use
 	getRestMux.HandleFunc("/rest/debug/peerCompletion", s.getPeerCompletion)
+	getRestMux.HandleFunc("/rest/debug/httpmetrics", s.getSystemHTTPMetrics)
 
 	// A handler that splits requests between the two above and disables
 	// caching
-	restMux := noCacheMiddleware(getPostHandler(getRestMux, postRestMux))
+	restMux := noCacheMiddleware(metricsMiddleware(getPostHandler(getRestMux, postRestMux)))
 
 	// The main routing handler
 	mux := http.NewServeMux()
@@ -320,6 +322,15 @@ func debugMiddleware(h http.Handler) http.Handler {
 	})
 }
 
+func metricsMiddleware(h http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		t := metrics.GetOrRegisterTimer(r.URL.Path, nil)
+		t0 := time.Now()
+		h.ServeHTTP(w, r)
+		t.UpdateSince(t0)
+	})
+}
+
 func redirectToHTTPSMiddleware(h http.Handler) http.Handler {
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		// Add a generous access-control-allow-origin header since we may be
@@ -743,6 +754,26 @@ func (s *apiSvc) getSystemLogTxt(w http.ResponseWriter, r *http.Request) {
 	}
 }
 
+func (s *apiSvc) getSystemHTTPMetrics(w http.ResponseWriter, r *http.Request) {
+	stats := make(map[string]interface{})
+	metrics.Each(func(name string, intf interface{}) {
+		if m, ok := intf.(*metrics.StandardTimer); ok {
+			pct := m.Percentiles([]float64{0.50, 0.95, 0.99})
+			for i := range pct {
+				pct[i] /= 1e6 // ns to ms
+			}
+			stats[name] = map[string]interface{}{
+				"count":         m.Count(),
+				"sumMs":         m.Sum() / 1e6, // ns to ms
+				"ratesPerS":     []float64{m.Rate1(), m.Rate5(), m.Rate15()},
+				"percentilesMs": pct,
+			}
+		}
+	})
+	bs, _ := json.MarshalIndent(stats, "", "  ")
+	w.Write(bs)
+}
+
 func (s *apiSvc) getSystemDiscovery(w http.ResponseWriter, r *http.Request) {
 	w.Header().Set("Content-Type", "application/json; charset=utf-8")
 	devices := make(map[string]discover.CacheEntry)