Major Description
The behaviour we observed was that a zookeeper election took about 2s plus 1.5s for reading the zoo_data snapshot. During this time solr tried to establish connections to any zookeeper in the ensemble but only succeeded once a leader was elected and that leader was done reading the snapshot. Solr document updates were slowed down during this time window.
Is this expected to happen during and shortly after elections, that is zookeeper closing existing connections, rejecting new connections and thus stalling solr updates?
Other than avoiding zookeeper elections, are there ways of reducing their impact on solr?
zookeeper log extract
08:18:54,968 [QuorumCnxManager.java:762] Connection broken for id ... 08:18:56,916 [Leader.java:345] LEADING - LEADER ELECTION TOOK - 1941 08:18:56,918 [FileSnap.java:83] Reading snapshot ... ... 08:18:57,010 [NIOServerCnxnFactory.java:197] Accepted socket connection from ... 08:18:57,010 [NIOServerCnxn.java:354] Exception causing close of session 0x0 due to java.io.IOException: ZooKeeperServer not running 08:18:57,010 [NIOServerCnxn.java:1001] Closed socket connection for client ... (no session established for client) ... 08:18:58,496 [FileTxnSnapLog.java:240] Snapshotting: ... to ...
solr log extract
08:18:54,968 [ClientCnxn.java:1085] Unable to read additional data from server sessionid ... likely server has closed socket, closing socket connection and attempting reconnect 08:18:55,068 [ConnectionManager.java:72] Watcher org.apache.solr.common.cloud.ConnectionManager@... name:ZooKeeperConnection Watcher:host1:port1,host2:port2,host3:port3,... got event WatchedEvent state:Disconnected type:None path:null path:null type:None 08:18:55,068 [ConnectionManager.java:132] zkClient has disconnected ... 08:18:55,961 [ClientCnxn.java:966] Opening socket connection to server ... 08:18:55,961 [ClientCnxn.java:849] Socket connection established to ... 08:18:55,962 [ClientCnxn.java:1085] Unable to read additional data from server sessionid ... likely server has closed socket, closing socket connection and attempting reconnect ... 08:18:56,714 [ClientCnxn.java:966] Opening socket connection to server ... 08:18:56,715 [ClientCnxn.java:849] Socket connection established to ... 08:18:56,715 [ClientCnxn.java:1085] Unable to read additional data from ... ... 08:18:57,640 [ClientCnxn.java:966] Opening socket connection to server ... 08:18:57,641 [ClientCnxn.java:849] Socket connection established to ... 08:18:57,641 [ClientCnxn.java:1085] Unable to read additional data from ... ... 08:18:58,352 [ClientCnxn.java:966] Opening socket connection to server ... 08:18:58,353 [ClientCnxn.java:849] Socket connection established to ... 08:18:58,353 [ClientCnxn.java:1085] Unable to read additional data from ... ... 08:18:58,749 [ClientCnxn.java:966] Opening socket connection to server ... 08:18:58,749 [ClientCnxn.java:849] Socket connection established to ... 08:18:58,751 [ClientCnxn.java:1207] Session establishment complete on server ... sessionid = ..., negotiated timeout = ... 08:18:58,751 ... [ConnectionManager.java:72] Watcher org.apache.solr.common.cloud.ConnectionManager@... name:ZooKeeperConnection Watcher:host1:port1,host2:port2,host3:port3,... got event WatchedEvent state:SyncConnected type:None path:null path:null type:None