Export a metrics endpoint for monitoring

glide.yaml

@@ -5,3 +5,6 @@ import:
 - package: golang.org/x/net
   subpackages:
   - websocket
+- package: github.com/prometheus/client_golang
+  subpackages:
+  - prometheus

router/metrics.go

@@ -0,0 +1,21 @@
+package router
+
+import (
+	"github.com/prometheus/client_golang/prometheus"
+	"net/http"
+)
+
+// Pump message send counter
+var pumpMsgSend *prometheus.CounterVec
+
+func init() {
+	pumpMsgSend = prometheus.NewCounterVec(
+		prometheus.CounterOpts{
+			Name: "pump_msg_send",
+			Help: "Number of message sent",
+		},
+		[]string{"container_id"},
+	)
+	prometheus.MustRegister(pumpMsgSend)
+	HttpHandlers.Register(func() http.Handler { return prometheus.Handler() }, "metrics")
+}

router/pump.go

@@ -11,6 +11,7 @@ import (
 	"time"
 
 	"github.com/fsouza/go-dockerclient"
+	"github.com/prometheus/client_golang/prometheus"
 )
 
 var allowTTY bool
@@ -354,6 +355,7 @@ func newContainerPump(container *docker.Container, stdout, stderr io.Reader) *co
 				}
 				return
 			}
+			pumpMsgSend.With(prometheus.Labels{"container_id": container.ID}).Inc()
 			cp.send(&Message{
 				Data:      strings.TrimSuffix(line, "\n"),
 				Container: container,