feat(api): add varz endpoint with metrics

pkg/api/routes.go

@@ -30,4 +30,9 @@ var routes = Routes{
 		"/healtz",
 		healthz,
 	},
+	Route{
+		"GET",
+		"/varz",
+		varz,
+	},
 }

pkg/api/varz.go

@@ -0,0 +1,25 @@
+package api
+
+import (
+	"expvar"
+	"fmt"
+	"net/http"
+
+	"github.com/ncarlier/webhookd/pkg/config"
+)
+
+func varz(conf *config.Config) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/json")
+		fmt.Fprintf(w, "{\n")
+		first := true
+		expvar.Do(func(kv expvar.KeyValue) {
+			if !first {
+				fmt.Fprintf(w, ",\n")
+			}
+			first = false
+			fmt.Fprintf(w, "%q: %s", kv.Key, kv.Value)
+		})
+		fmt.Fprintf(w, "\n}\n")
+	})
+}

pkg/metric/metric.go

@@ -0,0 +1,35 @@
+package metric
+
+import (
+	"expvar"
+	"runtime"
+	"time"
+)
+
+var startTime = time.Now().UTC()
+
+func goroutines() interface{} {
+	return runtime.NumGoroutine()
+}
+
+// uptime is an expvar.Func compliant wrapper for uptime info.
+func uptime() interface{} {
+	uptime := time.Since(startTime)
+	return int64(uptime)
+}
+
+var stats = expvar.NewMap("hookstats")
+
+var (
+	// Requests count the number of request
+	Requests expvar.Int
+	// RequestsFailed count the number of failed request
+	RequestsFailed expvar.Int
+)
+
+func init() {
+	stats.Set("requests", &Requests)
+	stats.Set("requests_failed", &RequestsFailed)
+	expvar.Publish("goroutines", expvar.Func(goroutines))
+	expvar.Publish("uptime", expvar.Func(uptime))
+}

pkg/worker/worker.go

@@ -3,6 +3,8 @@ package worker
 import (
 	"fmt"
 
+	"github.com/ncarlier/webhookd/pkg/metric"
+
 	"github.com/ncarlier/webhookd/pkg/logger"
 	"github.com/ncarlier/webhookd/pkg/model"
 	"github.com/ncarlier/webhookd/pkg/notification"
@@ -42,8 +44,10 @@ func (w Worker) Start() {
 			case work := <-w.Work:
 				// Receive a work request.
 				logger.Debug.Printf("Worker #%d received work request: %s#%d\n", w.ID, work.Name, work.ID)
+				metric.Requests.Add(1)
 				err := run(&work)
 				if err != nil {
+					metric.RequestsFailed.Add(1)
 					work.MessageChan <- []byte(fmt.Sprintf("error: %s", err.Error()))
 				} else {
 					work.MessageChan <- []byte("done")