Initial support for tracking connection metrics

cmd/mc-router/main.go

@@ -25,6 +25,7 @@ var (
 	cpuProfile     = flag.String("cpu-profile", "", "Enables CPU profiling and writes to given path")
 	debug          = flag.Bool("debug", false, "Enable debug logs")
 	connRateLimit  = flag.Int("connection-rate-limit", 1, "Max number of connections to allow per second")
+	metricsBackend = flag.String("metrics-backend", "discard", "Backend to use for metrics exposure/publishing: discard,expvar")
 )
 
 var (
@@ -67,6 +68,8 @@ func main() {
 
 	ctx, cancel := context.WithCancel(context.Background())
 
+	metricsBuilder := NewMetricsBuilder()
+
 	c := make(chan os.Signal, 1)
 	signal.Notify(c, syscall.SIGINT, syscall.SIGTERM)
 
@@ -75,7 +78,8 @@ func main() {
 	if *connRateLimit < 1 {
 		*connRateLimit = 1
 	}
-	server.Connector.StartAcceptingConnections(ctx, net.JoinHostPort("", strconv.Itoa(*port)), *connRateLimit)
+	connector := server.NewConnector(metricsBuilder.BuildConnectorMetrics())
+	connector.StartAcceptingConnections(ctx, net.JoinHostPort("", strconv.Itoa(*port)), *connRateLimit)
 
 	if *apiBinding != "" {
 		server.StartApiServer(*apiBinding)

cmd/mc-router/metrics.go

@@ -0,0 +1,48 @@
+package main
+
+import (
+	discardMetrics "github.com/go-kit/kit/metrics/discard"
+	expvarMetrics "github.com/go-kit/kit/metrics/expvar"
+	"github.com/itzg/mc-router/server"
+	"github.com/sirupsen/logrus"
+)
+
+type MetricsBuilder interface {
+	BuildConnectorMetrics() *server.ConnectorMetrics
+}
+
+func NewMetricsBuilder() MetricsBuilder {
+	switch *metricsBackend {
+	case "discard":
+		return &discardMetricsBuilder{}
+	case "expvar":
+		return &expvarMetricsBuilder{}
+	default:
+		logrus.Fatalf("Unsupported metrics backend: %s", metricsBackend)
+		return nil
+	}
+}
+
+type expvarMetricsBuilder struct {
+}
+
+func (b expvarMetricsBuilder) BuildConnectorMetrics() *server.ConnectorMetrics {
+	return &server.ConnectorMetrics{
+		Errors:            expvarMetrics.NewCounter("errors").With("subsystem", "connector"),
+		BytesTransmitted:  expvarMetrics.NewCounter("bytes"),
+		Connections:       expvarMetrics.NewCounter("connections"),
+		ActiveConnections: expvarMetrics.NewGauge("active_connections"),
+	}
+}
+
+type discardMetricsBuilder struct {
+}
+
+func (b discardMetricsBuilder) BuildConnectorMetrics() *server.ConnectorMetrics {
+	return &server.ConnectorMetrics{
+		Errors:            discardMetrics.NewCounter(),
+		BytesTransmitted:  discardMetrics.NewCounter(),
+		Connections:       discardMetrics.NewCounter(),
+		ActiveConnections: discardMetrics.NewGauge(),
+	}
+}