Add basic prometheus metrics

webhook.go

@@ -21,11 +21,16 @@ import (
 
 	chimiddleware "github.com/go-chi/chi/middleware"
 	"github.com/gorilla/mux"
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promauto"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
+
 	fsnotify "gopkg.in/fsnotify.v1"
 )
 
 const (
 	version          = "2.8.0"
+	metricsNamespace = "webhook"
 )
 
 var (
@@ -52,6 +57,7 @@ var (
 	setUID             = flag.Int("setuid", 0, "set user ID after opening listening port; must be used with setgid")
 	httpMethods        = flag.String("http-methods", "", `set default allowed HTTP methods (ie. "POST"); separate methods with comma`)
 	pidPath            = flag.String("pidfile", "", "create PID file at the given path")
+	metrics            = flag.Bool("metrics", false, "enable prometheus metrics at /metrics")
 
 	responseHeaders hook.ResponseHeaders
 	hooksFiles      hook.HooksFiles
@@ -63,6 +69,31 @@ var (
 	pidFile *pidfile.PIDFile
 )
 
+// prometheus metrics
+var hookCounter = promauto.NewCounterVec(
+	prometheus.CounterOpts{
+		Namespace: metricsNamespace,
+		Name:      "hook_requests_total",
+		Help:      "Total number of hook requests",
+	}, []string{"hook"},
+)
+
+var hookErrorCounter = promauto.NewCounterVec(
+	prometheus.CounterOpts{
+		Namespace: metricsNamespace,
+		Name:      "hook_errors_total",
+		Help:      "Total number of hook errors",
+	}, []string{"hook", "error"},
+)
+
+var hookSuccessCounter = promauto.NewCounterVec(
+	prometheus.CounterOpts{
+		Namespace: metricsNamespace,
+		Name:      "hook_success_total",
+		Help:      "Total number of successful hook executions",
+	}, []string{"hook"},
+)
+
 func matchLoadedHook(id string) *hook.Hook {
 	for _, hooks := range loadedHooksFromFiles {
 		if hook := hooks.Match(id); hook != nil {
@@ -270,6 +301,11 @@ func main() {
 
 	r.HandleFunc(hooksURL, hookHandler)
 
+	if *metrics {
+		// add /metrics handler
+		r.Handle("/metrics", promhttp.Handler())
+	}
+
 	// Create common HTTP server settings
 	svr := &http.Server{
 		Addr:    addr,
@@ -315,6 +351,8 @@ func hookHandler(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	hookCounter.With(prometheus.Labels{"hook": matchedHook.ID}).Inc()
+
 	// Check for allowed methods
 	var allowedMethod bool
 
@@ -340,6 +378,8 @@ func hookHandler(w http.ResponseWriter, r *http.Request) {
 	}
 
 	if !allowedMethod {
+		hookErrorCounter.With(prometheus.Labels{"hook": matchedHook.ID, "error": "invalid_method"}).Inc()
+
 		w.WriteHeader(http.StatusMethodNotAllowed)
 		log.Printf("[%s] HTTP %s method not allowed for hook %q", req.ID, r.Method, id)
 
@@ -540,6 +580,8 @@ func hookHandler(w http.ResponseWriter, r *http.Request) {
 		writeHttpResponseCode(w, req.ID, matchedHook.ID, matchedHook.TriggerRuleMismatchHttpResponseCode)
 	}
 
+	hookErrorCounter.With(prometheus.Labels{"hook": matchedHook.ID, "error": "rules"}).Inc()
+
 	// if none of the hooks got triggered
 	log.Printf("[%s] %s got matched, but didn't get triggered because the trigger rules were not satisfied\n", req.ID, matchedHook.ID)
 
@@ -559,6 +601,7 @@ func handleHook(h *hook.Hook, r *hook.Request) (string, error) {
 
 	cmdPath, err := exec.LookPath(lookpath)
 	if err != nil {
+		hookErrorCounter.With(prometheus.Labels{"hook": h.ID, "error": "command"}).Inc()
 		log.Printf("[%s] error in %s", r.ID, err)
 
 		// check if parameters specified in execute-command by mistake
@@ -620,6 +663,7 @@ func handleHook(h *hook.Hook, r *hook.Request) (string, error) {
 	log.Printf("[%s] command output: %s\n", r.ID, out)
 
 	if err != nil {
+		hookErrorCounter.With(prometheus.Labels{"hook": h.ID, "error": "command"}).Inc()
 		log.Printf("[%s] error occurred: %+v\n", r.ID, err)
 	}
 
@@ -633,6 +677,8 @@ func handleHook(h *hook.Hook, r *hook.Request) (string, error) {
 		}
 	}
 
+	hookSuccessCounter.With(prometheus.Labels{"hook": h.ID}).Inc()
+
 	log.Printf("[%s] finished handling %s\n", r.ID, h.ID)
 
 	return string(out), err