Hi zookeeper-user, When I was triaging an issue with my ZK wrapper I think I found that during disconnection ZK client has failed to deliver the session event to the watcher (but logged it). The log shows: 2014-04-23 23:50:30,324:990(0x7f75d4ba9940):ZOO_INFO@check_events@1703: initiated connection to server [<...>:2181] 2014-04-23 23:50:31,603:990(0x7f75d4ba9940):ZOO_INFO@check_events@1750: session establishment complete on server [<...>:2181], sessionId=0x2456db1b7d32534, negotiated timeout=10000 ... 2014-04-23 23:50:38,925:990(0x7f75d4ba9940):ZOO_ERROR@handle_socket_error_msg@1643: Socket [<...>:2181] zk retcode=-7, errno=110(Connection timed out): connection to <...>:2181 timed out (exceeded timeout by 636ms) 2014-04-23 23:50:38,925:990(0x7f75d4ba9940):ZOO_WARN@zookeeper_interest@1557: Exceeded deadline by 1842ms 2014-04-23 23:50:38,925:990(0x7f75d4ba9940):ZOO_INFO@check_events@1703: initiated connection to server [<...>:2181] 2014-04-23 23:50:38,927:990(0x7f75d4ba9940):ZOO_INFO@check_events@1750: session establishment complete on server [<...>:2181], sessionId=0x2456db1b7d32534, negotiated timeout=10000 which indicates that ZK client state transitioned from CONNECTED -> CONNECTING -> CONNECTED. But my wrapper code was expecting a watcher event with ZOO_SESSION_EVENT & ZOO_CONNECTING_STATE but never got one. The events for the CONNECTED state before and after the disconnection were delivered. Has anyone seen this before? This is C client 3.4.5. Thanks! Yan