Add Prometheus instrumentation and liveness/readiness probes

pkg/controller/controller.go

@@ -2,9 +2,8 @@ package controller
 
 import (
 	"fmt"
-	"time"
-
 	"sync"
+	"time"
 
 	"github.com/google/go-cmp/cmp"
 	sharedclientset "github.com/knative/pkg/client/clientset/versioned"

pkg/server/server.go

@@ -0,0 +1,47 @@
+package server
+
+import (
+	"context"
+	"net/http"
+	"time"
+
+	"github.com/prometheus/client_golang/prometheus/promhttp"
+	"go.uber.org/zap"
+)
+
+func ListenAndServe(port string, timeout time.Duration, logger *zap.SugaredLogger, stopCh <-chan struct{}) {
+	mux := http.DefaultServeMux
+	mux.Handle("/metrics", promhttp.Handler())
+	mux.HandleFunc("/healthz", func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusOK)
+		w.Write([]byte("OK"))
+	})
+
+	srv := &http.Server{
+		Addr:         ":" + port,
+		Handler:      mux,
+		ReadTimeout:  5 * time.Second,
+		WriteTimeout: 1 * time.Minute,
+		IdleTimeout:  15 * time.Second,
+	}
+
+	logger.Infof("Starting HTTP server on port %s", port)
+
+	// run server in background
+	go func() {
+		if err := srv.ListenAndServe(); err != http.ErrServerClosed {
+			logger.Fatalf("HTTP server crashed %v", err)
+		}
+	}()
+
+	// wait for SIGTERM or SIGINT
+	<-stopCh
+	ctx, cancel := context.WithTimeout(context.Background(), timeout)
+	defer cancel()
+
+	if err := srv.Shutdown(ctx); err != nil {
+		logger.Errorf("HTTP server graceful shutdown failed %v", err)
+	} else {
+		logger.Info("HTTP server stopped")
+	}
+}