TUN-2053: Add a /healthcheck endpoint to the metrics server

go.mod

@@ -57,6 +57,7 @@ require (
 	golang.org/x/sync v0.0.0-20190423024810-112230192c58
 	golang.org/x/sys v0.0.0-20191008105621-543471e840be
 	golang.org/x/text v0.3.2 // indirect
+	google.golang.org/appengine v1.4.0 // indirect
 	google.golang.org/genproto v0.0.0-20191007204434-a023cd5227bd // indirect
 	google.golang.org/grpc v1.24.0 // indirect
 	gopkg.in/coreos/go-oidc.v2 v2.1.0

metrics/metrics.go

@@ -2,6 +2,7 @@ package metrics
 
 import (
 	"context"
+	"fmt"
 	"net"
 	"net/http"
 	_ "net/http/pprof"
@@ -33,6 +34,9 @@ func ServeMetrics(l net.Listener, shutdownC <-chan struct{}, logger *logrus.Logg
 	}
 
 	http.Handle("/metrics", promhttp.Handler())
+	http.Handle("/healthcheck", http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		fmt.Fprintf(w, "OK\n")
+	}))
 
 	wg.Add(1)
 	go func() {