Added prometheus to README

README.md

@@ -70,6 +70,8 @@ Supported user databases (for user repository, with passwords or keys, if authen
 
 Redis can also be used for status and statistics storage and notification.
 
+By default a [prometheus](https://prometheus.io/) exporter endpoint is enabled on port 9121 under path /metrics
+
 Supported message integrity digest algorithms:
 
   * HMAC-SHA1, with MD5-hashed keys (as required by STUN and TURN standards)

README.turnserver

@@ -265,6 +265,9 @@ Flags:
 			check: across the session, all requests must have the same
 			main ORIGIN attribute value (if the ORIGIN was
 			initially used by the session).
+ --no-prometheus	Disable prometheus metrics. By default it is
+			enabled and listening on port 9121 unther the path /metrics
+            also the path / on this port can be used as a health check
 
 -h			Help.