zookeeper: Add a listener and log events

hbase-exporter

@@ -50,6 +50,10 @@ import xml.etree.ElementTree as et
 tmp_path = '/tmp/'
 logpath = tmp_path
 
+# ZooKeeper
+zk_address = 'localhost:2181'
+zk_reconnect_interval_s = 30
+
 # Prometheus
 prom_http_port = 9010
 prom_scrape_interval_s = 10
@@ -98,19 +102,36 @@ class zk():
 
         zk_client = kz_client.KazooClient(address)
         zk_client.add_listener(listener)
-        zk_client.start(timeout)
+
+        try:
+            zk_client.start(timeout)
+        except Exception as e:
+            logging.debug("ZooKeeper Error: " + str(e))
+            return False
+
         self.zk_client = zk_client
 
     @classmethod
     def get_znode_data(self, znode):
 
         try:
-            self.zk_client.get_children(znode)
+            self.zk_client.get(znode)
         except Exception as e:
             logging.debug("Type error: " + str(e))
             logging.info("ZooKeeper: Could not find znode: " + znode)
             return False
 
+    def listener(state):
+        if state == KazooState.LOST:
+            logging.debug("ZooKeeper: Connection lost")
+            # Register somewhere that the session was lost
+        elif state == KazooState.SUSPENDED:
+            logging.debug("ZooKeeper: Connection suspended")
+            # Handle being disconnected from Zookeeper
+        else:
+            logging.debug("ZooKeeper: Connection re-established")
+            # Handle being connected/reconnected to Zookeeper
+
 
 class jmx_query():
 
@@ -476,10 +497,14 @@ if __name__ == '__main__':
 
     logger = logging.getLogger(__name__)
 
-
-
     # Start the Prometheus server
-    start_http_server(prom_http_port)
+    try:
+        start_http_server(prom_http_port)
+    except Exception as e:
+        logging.debug("Failed to start Prometheus webserver: " + str(e))
+        logging.info("There might be another instance of " + sys.argv[0] + " already running, can not bind to " + str(prom_http_port) + ", exiting..")
+        sys.exit()
+
     nruns = 0
 
     if (args.hbase_masters is None):
@@ -491,8 +516,16 @@ if __name__ == '__main__':
         hdfs_namenode_port = hdfs_namenode_default_port
 
     # Start a ZooKeeper client
-    zk.main()
-    if cluster_is_kerbeized:
+    r = False
+
+    while not r:
+        logging.info("ZooKeeper: Trying to connect to " + zk_address)
+        r = zk.main(zk_address)
+        time.sleep(zk_reconnect_interval_s)
+
+    zk.add_listener(listener)
+
+    if cluster_is_kerberized:
         znode_clusterid("/hbase")
     else:
         znode_clusterid("/hbase-unsecure")