Add request duration metric

Author: Laurie T. Malau

components/public-api-server/middleware/prometheus.go

@@ -10,6 +10,7 @@ import (
 	gitpod "github.com/gitpod-io/gitpod/gitpod-protocol"
 	"github.com/grpc-ecosystem/go-grpc-middleware/logging/logrus/ctxlogrus"
 	"net/url"
+	"time"
 )
 
 type ServerConnectionPool interface {
@@ -26,6 +27,10 @@ type NoConnectionPool struct {
 func (p *NoConnectionPool) Get(ctx context.Context, token string) (gitpod.APIInterface, error) {
 	logger := ctxlogrus.Extract(ctx)
 
+	start := time.Now()
+	defer func() {
+		ReportConnectionDuration(time.Since(start))
+	}()
 	server, err := gitpod.ConnectToServer(p.ServerAPI.String(), gitpod.ConnectToServerOpts{
 		Context: ctx,
 		Token:   token,

components/public-api-server/pkg/proxy/conn.go

@@ -0,0 +1,20 @@
+// Copyright (c) 2022 Gitpod GmbH. All rights reserved.
+// Licensed under the GNU Affero General Public License (AGPL).
+// See License-AGPL.txt in the project root for license information.
+
+package proxy
+
+import (
+	"github.com/prometheus/client_golang/prometheus"
+	"time"
+)
+
+func ReportConnectionDuration(d time.Duration) {
+	ConnectionDurationHistogram.Observe(d.Seconds())
+}
+
+var ConnectionDurationHistogram = prometheus.NewHistogram(prometheus.HistogramOpts{
+	Namespace: "gitpod",
+	Name:      "grpc_connection_duration_seconds",
+	Help:      "Histogram of connection time in seconds",
+})

components/public-api-server/pkg/proxy/prometheusmetrics.go

@@ -12,21 +12,25 @@ import (
 	"github.com/gitpod-io/gitpod/public-api-server/pkg/apiv1"
 	"github.com/gitpod-io/gitpod/public-api-server/pkg/proxy"
 	v1 "github.com/gitpod-io/gitpod/public-api/v1"
+	"github.com/prometheus/client_golang/prometheus"
 	"github.com/sirupsen/logrus"
 	"net/http"
 )
 
 func Start(logger *logrus.Entry, cfg Config) error {
+	registry := prometheus.NewRegistry()
+
 	srv, err := baseserver.New("public_api_server",
 		baseserver.WithLogger(logger),
 		baseserver.WithHTTPPort(cfg.HTTPPort),
 		baseserver.WithGRPCPort(cfg.GRPCPort),
+		baseserver.WithMetricsRegistry(registry),
 	)
 	if err != nil {
 		return fmt.Errorf("failed to initialize public api server: %w", err)
 	}
 
-	if registerErr := register(srv, cfg); registerErr != nil {
+	if registerErr := register(srv, cfg, registry); registerErr != nil {
 		return fmt.Errorf("failed to register services: %w", registerErr)
 	}
 
@@ -37,7 +41,9 @@ func Start(logger *logrus.Entry, cfg Config) error {
 	return nil
 }
 
-func register(srv *baseserver.Server, cfg Config) error {
+func register(srv *baseserver.Server, cfg Config, registry *prometheus.Registry) error {
+	registry.MustRegister(proxy.ConnectionDurationHistogram)
+
 	logger := log.New()
 	m := middleware.NewLoggingMiddleware(logger)
 	srv.HTTPMux().Handle("/", m(http.HandlerFunc(HelloWorldHandler)))