Merge pull request #7 from monobaila/override_service_health

Update zk_service_health metric when not serving.

README.md

@@ -54,7 +54,8 @@ All metrics are reported with the `plugin:zookeeper` dimension. Additionally,
 if you specify an `Instance` in your `Module` configuration block, its value
 will be reported as the `plugin_instance` dimension.
 
-zk_is_leader is a synthetic metric which is 0 iff the contents of zk_server_state is 'follower'
+zk_is_leader is a synthetic metric which is 0 if the contents of zk_server_state is 'follower'.
+zk_service_health is a synthetic metric which tracks if service is running and servicing requests.
 
 # License
 

zk-collectd.py

@@ -84,6 +84,15 @@ def _get_mntr_stats(self):
         response = self._send_cmd(MNTR_CMD)
         result = {}
 
+        # If instance stops serving requests (e.g. loses quorum) it still
+        # returns "imok" to ruok query but will force close any client
+        # connections and return an error string to all other 4 letter commands.
+        # In this situation we should override zk_service_health metric
+        # initially set in _get_health_stat as it's definitely not in a healthy
+        # state.
+        if response == 'This ZooKeeper instance is not currently serving requests\n':
+            return {'zk_service_health': 0}
+
         for line in response.splitlines():
             try:
                 key, value = self._parse_line(line)