TUN-528: Move cloudflared into a separate repo

metrics/metrics.go

@@ -0,0 +1,72 @@
+package metrics
+
+import (
+	"net"
+	"net/http"
+	_ "net/http/pprof"
+	"runtime"
+	"sync"
+	"time"
+
+	"golang.org/x/net/context"
+	"golang.org/x/net/trace"
+
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
+	"github.com/sirupsen/logrus"
+)
+
+const (
+	shutdownTimeout = time.Second * 15
+	startupTime     = time.Millisecond * 500
+)
+
+func ServeMetrics(l net.Listener, shutdownC <-chan struct{}, logger *logrus.Logger) (err error) {
+	var wg sync.WaitGroup
+	// Metrics port is privileged, so no need for further access control
+	trace.AuthRequest = func(*http.Request) (bool, bool) { return true, true }
+	// TODO: parameterize ReadTimeout and WriteTimeout. The maximum time we can
+	// profile CPU usage depends on WriteTimeout
+	server := &http.Server{
+		ReadTimeout:  10 * time.Second,
+		WriteTimeout: 10 * time.Second,
+	}
+
+	http.Handle("/metrics", promhttp.Handler())
+
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+		err = server.Serve(l)
+	}()
+	logger.WithField("addr", l.Addr()).Info("Starting metrics server")
+	// server.Serve will hang if server.Shutdown is called before the server is
+	// fully started up. So add artificial delay.
+	time.Sleep(startupTime)
+
+	<-shutdownC
+	ctx, cancel := context.WithTimeout(context.Background(), shutdownTimeout)
+	server.Shutdown(ctx)
+	cancel()
+
+	wg.Wait()
+	if err == http.ErrServerClosed {
+		logger.Info("Metrics server stopped")
+		return nil
+	}
+	logger.WithError(err).Error("Metrics server quit with error")
+	return err
+}
+
+func RegisterBuildInfo(buildTime string, version string) {
+	buildInfo := prometheus.NewGaugeVec(
+		prometheus.GaugeOpts{
+			// Don't namespace build_info, since we want it to be consistent across all Cloudflare services
+			Name: "build_info",
+			Help: "Build and version information",
+		},
+		[]string{"goversion", "revision", "version"},
+	)
+	prometheus.MustRegister(buildInfo)
+	buildInfo.WithLabelValues(runtime.Version(), buildTime, version).Set(1)
+}