Added http health check endpoint. (#137)

* Added http health check endpoint.

* Fixed performing POST on GET endpoint.

* Explicitly return http status 200 in health check endpoint.

* Updated changelog.

.gitignore

@@ -3,3 +3,4 @@ acme-dns.db
 acme-dns.log
 .vagrant
 coverage.out
+.idea/

README.md

@@ -102,6 +102,28 @@ The method allows you to update the TXT answer contents of your unique subdomain
 }
 ```
 
+### Health check endpoint
+
+The method can be used to check readiness and/or liveness of the server. It will return status code 200 on success or won't be reachable.
+
+```GET /health```
+
+#### Example using a Kubernetes deployment
+
+```
+# ...
+readinessProbe:
+  httpGet:
+    path: /health
+    port: 80
+  periodSeconds: 2
+  initialDelaySeconds: 2
+  failureThreshold: 3
+  successThreshold: 1
+livenessProbe:
+  # same as for readinessProbe...
+```
+
 ## Self-hosted
 
 You are encouraged to run your own acme-dns instance, because you are effectively authorizing the acme-dns server to act on your behalf in providing the answer to the challenging CA, making the instance able to request (and get issued) a TLS certificate for the domain that has CNAME pointing to it.
@@ -304,6 +326,8 @@ logformat = "text"
 ## Changelog
 
 - master
+   - Unreleased
+      - Added new endpoint to perform health checks
    - Changed
       - A new protocol selection for DNS server "both", that binds both - UDP and TCP ports.
 - v0.6

api.go

@@ -93,3 +93,8 @@ func webUpdatePost(w http.ResponseWriter, r *http.Request, _ httprouter.Params)
 	w.WriteHeader(updStatus)
 	w.Write(upd)
 }
+
+// Endpoint used to check the readiness and/or liveness (health) of the server.
+func healthCheck(w http.ResponseWriter, r *http.Request, _ httprouter.Params) {
+	w.WriteHeader(http.StatusOK)
+}

api_test.go

@@ -71,6 +71,7 @@ func setupRouter(debug bool, noauth bool) http.Handler {
 		Debug:              Config.General.Debug,
 	})
 	api.POST("/register", webRegisterPost)
+	api.GET("/health", healthCheck)
 	if noauth {
 		api.POST("/update", noAuth(webUpdatePost))
 	} else {
@@ -406,3 +407,11 @@ func TestApiManyUpdateWithIpCheckHeaders(t *testing.T) {
 	}
 	Config.API.UseHeader = false
 }
+
+func TestApiHealthCheck(t *testing.T) {
+	router := setupRouter(false, false)
+	server := httptest.NewServer(router)
+	defer server.Close()
+	e := getExpect(t, server)
+	e.GET("/health").Expect().Status(http.StatusOK)
+}

main.go

@@ -128,6 +128,7 @@ func startHTTPAPI(errChan chan error) {
 		api.POST("/register", webRegisterPost)
 	}
 	api.POST("/update", Auth(webUpdatePost))
+	api.GET("/health", healthCheck)
 
 	host := Config.API.IP + ":" + Config.API.Port