Add a simple health check

README.md

@@ -53,6 +53,18 @@ expected by Go's http.Server.
 Prometheus metric serving (though not metric aggregation) can be
 disabled by passing ``--disable-prometheus`` on the command line.
 
+## Health Check Integration
+
+A simple health check can be enabled by passing `--enable-health-check` 
+on the command line. A JSON response will be served on `:3000` at the 
+path `/health` by default. The bind address and port can be
+customized by passing `--health-check-bind=bind-string` in the format
+expected by Go's http.Server. A sample response:
+
+```json
+{ "name": "ses-smtp-proxy", "status": "ok", "version": "v1.3.0" }
+```
+
 ## Usage
 By default the command takes no arguments and will listen on port 2500 on all
 interfaces. The listen interfaces and port can be specified as the only

main.go

@@ -245,6 +245,8 @@ func main() {
 	vaultPath := flag.String("vault-path", "", "Full path to Vault credential (ex: \"aws/creds/my-mail-user\")")
 	showVersion := flag.Bool("version", false, "Show program version")
 	configurationSetName := flag.String("configuration-set-name", "", "Configuration set name with which SendRawEmail will be invoked")
+	enableHealthCheck := flag.Bool("enable-health-check", false, "Enable health check server")
+	healthCheckBind := flag.String("health-check-bind", ":3000", "Address/port on which to bind health check server")
 
 	flag.Parse()
 
@@ -253,6 +255,16 @@ func main() {
 		return
 	}
 
+	if *enableHealthCheck {
+		sm := http.NewServeMux()
+		ps := &http.Server{Addr: *healthCheckBind, Handler: sm}
+		sm.Handle("/health", http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			w.Header().Add("Content-Type", "application/json")
+			w.Write([]byte("{\"name\": \"ses-smtp-proxy\", \"status\": \"ok\", \"version\": \"" + version + "\"}"))
+		}))
+		go ps.ListenAndServe()
+	}
+
 	credentialError := make(chan error, 2)
 	sesClient, err := makeSesClient(ctx, *enableVault, *vaultPath, credentialError)
 	if err != nil {