From 96e120f1e916e2a1ce534fa4bcaa584f48a5204a Mon Sep 17 00:00:00 2001
From: Daniel Muehlbachler-Pietrzykowski <daniel@muehlbachler.io>
Date: Fri, 4 Oct 2024 10:27:41 +0200
Subject: [PATCH] feat: add metrics endpoint

---
 Dockerfile                        |  2 +-
 cmd/webhook/init/server/server.go |  2 ++
 pkg/webhook/webhook.go            | 12 ++++++++++++
 3 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/Dockerfile b/Dockerfile
index d60a6d2..4a94b05 100644
--- a/Dockerfile
+++ b/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"]
diff --git a/cmd/webhook/init/server/server.go b/cmd/webhook/init/server/server.go
index 3a64085..f97b7a3 100644
--- a/cmd/webhook/init/server/server.go
+++ b/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() {
diff --git a/pkg/webhook/webhook.go b/pkg/webhook/webhook.go
index b0a0478..5edbd72 100644
--- a/pkg/webhook/webhook.go
+++ b/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 {