feat: add metrics (#2)

* feat: add metrics

* docs: update README with metrics

* feat(metrics): add http metrics

Author: acamilleri

README.md

@@ -65,6 +65,15 @@ func main() {
 }
 ```
 
+### Metrics
+
+The Run function running a metrics handler to have some metrics about the
+events handler  and actions executed.
+
+Metrics are expose at `/metrics` path in [Prometheus](https://prometheus.io/) format.
+
+You can find all metrics [available here](metrics.go)
+
 ## Contributing
 Pull requests are welcome. For major changes, please open an issue first to discuss what you would like to change.
 

app.go

@@ -5,7 +5,11 @@ import (
 	"fmt"
 	"net"
 	"net/http"
+	"strconv"
+	"time"
 
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
 	"github.com/sirupsen/logrus"
 
 	"github.com/acamilleri/go-plexhooks/plex"
@@ -47,30 +51,73 @@ func (a *App) Run() error {
 	}
 
 	http.HandleFunc("/events", a.handler())
+	http.Handle("/metrics", promhttp.Handler())
 
 	a.log.Infof("running server on %s", a.listenAddr)
 	return http.ListenAndServe(a.listenAddr.String(), nil)
 }
 
 func (a *App) handler() http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
+		var statusCode int = http.StatusOK
 		defer r.Body.Close()
-		w.WriteHeader(http.StatusOK)
 
-		event, err := parseRequest(r)
-		if err != nil {
-			a.log.WithError(err).Error("failed to parse request")
+		trackRequestDuration := newTrackRequestDuration(r.Method, "/events")
+		if r.Method != http.MethodPost {
+			statusCode = http.StatusMethodNotAllowed
+			w.WriteHeader(statusCode)
+			time.Sleep(time.Second * 5)
+			httpRequestTotal.With(prometheus.Labels{
+				"handler": "/events",
+				"method":  r.Method,
+				"code":    strconv.Itoa(statusCode),
+			}).Inc()
+			trackRequestDuration.Finish()
+			return
 		}
 
-		a.log.Infof("%s event handled", event.Name)
-		err = a.triggerActionsOnEvent(event)
+		err := a.handleRequest(r)
 		if err != nil {
-			a.log.WithError(err).Errorf("%s event actions failed", event.Name)
+			statusCode = http.StatusInternalServerError
+			w.WriteHeader(statusCode)
+			trackRequestDuration.Finish()
+			httpRequestTotal.With(prometheus.Labels{
+				"handler": "/events",
+				"method":  r.Method,
+				"code":    strconv.Itoa(statusCode),
+			}).Inc()
+			return
 		}
+
+		w.WriteHeader(statusCode)
+		trackRequestDuration.Finish()
+		httpRequestTotal.With(prometheus.Labels{
+			"handler": "/events",
+			"method":  r.Method,
+			"code":    strconv.Itoa(statusCode),
+		}).Inc()
 	}
 }
 
+func (a *App) handleRequest(r *http.Request) error {
+	event, err := parseRequest(r)
+	if err != nil {
+		a.log.WithError(err).Error("failed to parse request")
+		return err
+	}
+
+	a.log.Infof("%s event handled", event.Name)
+	err = a.triggerActionsOnEvent(event)
+	if err != nil {
+		a.log.WithError(err).Errorf("%s event actions failed", event.Name)
+		return err
+	}
+
+	return nil
+}
+
 func (a *App) triggerActionsOnEvent(event plex.Event) error {
+	eventsReceivedTotal.With(prometheus.Labels{"event": event.Name.String()}).Inc()
 	hookName := event.Name
 
 	actions := a.actions.GetByHook(hookName)
@@ -80,15 +127,26 @@ func (a *App) triggerActionsOnEvent(event plex.Event) error {
 
 	for _, action := range actions {
 		name := action.Name()
+		actionDuration := newTrackActionDuration(event, action)
 
 		a.log.Debugf("action %s triggered", name)
 		err := action.Execute(event)
 		if err != nil {
 			a.log.WithError(err).Errorf("action %s failed", name)
+			actionsErrorTotal.With(
+				prometheus.Labels{"event": event.Name.String(), "action": action.Name()},
+			).Inc()
+			actionDuration.Finish()
 			continue
 		}
+
 		a.log.Infof("action %s success", name)
+		actionDuration.Finish()
+		actionsSuccessTotal.With(
+			prometheus.Labels{"event": event.Name.String(), "action": action.Name()},
+		).Inc()
 	}
+
 	return nil
 }
 

metrics.go

@@ -0,0 +1,113 @@
+package plexhooks
+
+import (
+	"time"
+
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promauto"
+
+	"github.com/acamilleri/go-plexhooks/plex"
+)
+
+var (
+	httpRequestDuration = promauto.NewHistogramVec(prometheus.HistogramOpts{
+		Namespace: "plexhooks",
+		Subsystem: "http",
+		Name:      "request_duration_seconds",
+		Help:      "The latency of the HTTP requests.",
+		Buckets:   prometheus.DefBuckets,
+	}, []string{"handler", "method"})
+
+	httpRequestTotal = promauto.NewCounterVec(prometheus.CounterOpts{
+		Namespace: "plexhooks",
+		Subsystem: "http",
+		Name:      "request_total",
+		Help:      "How many http requests processed, partitioned by handler, status code and http method.",
+	}, []string{"handler", "method", "code"})
+
+	eventsReceivedTotal = promauto.NewCounterVec(
+		prometheus.CounterOpts{
+			Namespace: "plexhooks",
+			Subsystem: "events",
+			Name:      "received_total",
+			Help:      "Total number of events received.",
+		}, []string{"event"})
+
+	actionsSuccessTotal = promauto.NewCounterVec(
+		prometheus.CounterOpts{
+			Namespace: "plexhooks",
+			Subsystem: "actions",
+			Name:      "success_total",
+			Help:      "Total number of actions by hook executed with success.",
+		}, []string{"event", "action"})
+
+	actionsDurationDuration = promauto.NewHistogramVec(
+		prometheus.HistogramOpts{
+			Namespace: "plexhooks",
+			Subsystem: "actions",
+			Name:      "duration_seconds",
+			Help:      "A histogram of time to running action by hook.",
+			Buckets:   prometheus.DefBuckets,
+		}, []string{"event", "action"})
+
+	actionsErrorTotal = promauto.NewCounterVec(
+		prometheus.CounterOpts{
+			Namespace: "plexhooks",
+			Subsystem: "actions",
+			Name:      "error_total",
+			Help:      "Total number of actions by hook failed.",
+		}, []string{"event", "action"})
+)
+
+type trackActionDuration struct {
+	event  string
+	action string
+	start  time.Time
+	stop   time.Time
+}
+
+func newTrackActionDuration(event plex.Event, action Action) *trackActionDuration {
+	return &trackActionDuration{
+		event:  event.Name.String(),
+		action: action.Name(),
+		start:  time.Now(),
+		stop:   time.Time{},
+	}
+}
+
+func (track *trackActionDuration) Finish() {
+	track.stop = time.Now()
+
+	duration := track.stop.Sub(track.start).Seconds()
+	actionsDurationDuration.With(prometheus.Labels{
+		"event":  track.event,
+		"action": track.action,
+	}).Observe(duration)
+}
+
+type trackRequestDuration struct {
+	method  string
+	handler string
+
+	start time.Time
+	stop  time.Time
+}
+
+func newTrackRequestDuration(method, handler string) *trackRequestDuration {
+	return &trackRequestDuration{
+		method:  method,
+		handler: handler,
+		start:   time.Now(),
+		stop:    time.Time{},
+	}
+}
+
+func (track *trackRequestDuration) Finish() {
+	track.stop = time.Now()
+
+	duration := track.stop.Sub(track.start).Seconds()
+	httpRequestDuration.With(prometheus.Labels{
+		"method":  track.method,
+		"handler": track.handler,
+	}).Observe(duration)
+}

plex/model.go

@@ -1,5 +1,9 @@
 package plex
 
+import (
+	"strings"
+)
+
 const (
 	// LibraryOnDeck A new item is added that appears in the user’s On Deck.
 	// A poster is also attached to this event.
@@ -119,3 +123,7 @@ type Metadata struct {
 
 // Name Event Name
 type Name string
+
+func (name Name) String() string {
+	return strings.ToLower(string(name))
+}