feat: add metrics endpoint

Dockerfile

@@ -16,6 +16,6 @@ LABEL org.opencontainers.image.version="${CI_COMMIT_TAG}"
 USER 20000:20000
 COPY --chmod=555 external-dns-provider-adguard /opt/external-dns-provider-adguard/webhook
 
-EXPOSE 8888/tcp
+EXPOSE 8888/tcp 8080/tcp
 
 ENTRYPOINT ["/opt/external-dns-provider-adguard/webhook"]

cmd/webhook/init/server/server.go

@@ -44,10 +44,12 @@ func Init(config configuration.Config, p *webhook.Webhook) *http.Server {
 // Init server initialization function
 // The server will respond to the following endpoints:
 // - /healthz (GET): health check endpoint
+// - /metrics (GET): health metrics
 func InitHealthz(config configuration.Config, p *webhook.Webhook) *http.Server {
 	r := chi.NewRouter()
 
 	r.Get("/healthz", p.Health)
+	r.Get("/metrics", p.Metrics)
 
 	srv := createHTTPServer(fmt.Sprintf("%s:%d", config.HealthzHost, config.HealthzPort), r, config.ServerReadTimeout, config.ServerWriteTimeout)
 	go func() {

pkg/webhook/webhook.go

@@ -99,6 +99,18 @@ func (p *Webhook) Health(w http.ResponseWriter, r *http.Request) {
 	w.WriteHeader(http.StatusOK)
 }
 
+// Metrics handles the metrics request
+func (p *Webhook) Metrics(w http.ResponseWriter, r *http.Request) {
+	requestLog(r).Debug("requesting metrics")
+	s := p.provider.Health(r.Context())
+	err := json.NewEncoder(w).Encode(map[string]bool{"healthy": s})
+	if err != nil {
+		requestLog(r).WithField(logFieldError, err).Error("error encoding metrics")
+		w.WriteHeader(http.StatusInternalServerError)
+		return
+	}
+}
+
 // Records handles the get request for records
 func (p *Webhook) Records(w http.ResponseWriter, r *http.Request) {
 	if err := p.acceptHeaderCheck(w, r); err != nil {