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https://issues.apache.org/jira/browse/ZOOKEEPER-1419?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13232097#comment-13232097
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Camille Fournier commented on ZOOKEEPER-1419:
---------------------------------------------
I don't see why this is marked to 3.3.5, the logic there does not seem to be
faulty at a glance.
Do we want to add a test with a 5-member quorum or do we think the unit test on
the predicate logic is enough?
> Leader election never settles for a 5-node cluster
> --------------------------------------------------
>
> Key: ZOOKEEPER-1419
> URL: https://issues.apache.org/jira/browse/ZOOKEEPER-1419
> Project: ZooKeeper
> Issue Type: Bug
> Components: leaderElection
> Affects Versions: 3.4.3, 3.3.5, 3.5.0
> Environment: 64-bit Linux, all nodes running on the same machine
> (different ports)
> Reporter: Jeremy Stribling
> Assignee: Flavio Junqueira
> Priority: Blocker
> Fix For: 3.3.6, 3.4.4, 3.5.0
>
> Attachments: ZOOKEEPER-1419-fixed2.tgz, ZOOKEEPER-1419.patch,
> ZOOKEEPER-1419.patch, ZOOKEEPER-1419.patch
>
>
> We have a situation where it seems to my untrained eye that leader election
> never finishes for a 5-node cluster. In this test, all nodes are ZK 3.4.3
> and running on the same server (listening on different ports, of course).
> The nodes have server IDs of 0, 1, 2, 3, 4. The test brings up the cluster
> in different configurations, adding in a new node each time. We embed ZK in
> our application, so when we shut a node down and restart it with a new
> configuration, it all happens in a single JVM process. Here's our server
> startup code (for the case where there's more than one node in the cluster):
> {code}
> if (servers.size() > 1) {
> _log.debug("Starting Zookeeper server in quorum server mode");
> _quorum_peer = new QuorumPeer();
> synchronized(_quorum_peer) {
> _quorum_peer.setClientPortAddress(clientAddr);
> _quorum_peer.setTxnFactory(log);
> _quorum_peer.setQuorumPeers(servers);
> _quorum_peer.setElectionType(_election_alg);
> _quorum_peer.setMyid(_server_id);
> _quorum_peer.setTickTime(_tick_time);
> _quorum_peer.setInitLimit(_init_limit);
> _quorum_peer.setSyncLimit(_sync_limit);
> QuorumVerifier quorumVerifier =
> new QuorumMaj(servers.size());
> _quorum_peer.setQuorumVerifier(quorumVerifier);
> _quorum_peer.setCnxnFactory(_cnxn_factory);
> _quorum_peer.setZKDatabase(new ZKDatabase(log));
> _quorum_peer.start();
> }
> } else {
> _log.debug("Starting Zookeeper server in single server mode");
> _zk_server = new ZooKeeperServer();
> _zk_server.setTxnLogFactory(log);
> _zk_server.setTickTime(_tick_time);
> _cnxn_factory.startup(_zk_server);
> }
> {code}
> And here's our shutdown code:
> {code}
> if (_quorum_peer != null) {
> synchronized(_quorum_peer) {
> _quorum_peer.shutdown();
> FastLeaderElection fle =
> (FastLeaderElection) _quorum_peer.getElectionAlg();
> fle.shutdown();
> try {
> _quorum_peer.getTxnFactory().commit();
> } catch (java.nio.channels.ClosedChannelException e) {
> // ignore
> }
> }
> } else {
> _cnxn_factory.shutdown();
> _zk_server.getTxnLogFactory().commit();
> }
> {code}
> The test steps through the following scenarios in quick succession:
> Run 1: Start a 1-node cluster, servers=[0]
> Run 2: Start a 2-node cluster, servers=[0,3]
> Run 3: Start a 3-node cluster, servers=[0,1,3]
> Run 4: Start a 4-node cluster, servers=[0,1,2,3]
> Run 5: Start a 5-node cluster, servers=[0,1,2,3,4]
> It appears that run 5 never elects a leader -- the nodes just keep spewing
> messages like this (example from node 0):
> {noformat}
> 2012-03-14 16:23:12,775 13308 [WorkerSender[myid=0]] DEBUG
> org.apache.zookeeper.server.quorum.QuorumCnxManager - There is a connection
> already for server 2
> 2012-03-14 16:23:12,776 13309 [QuorumPeer[myid=0]/127.0.0.1:2900] DEBUG
> org.apache.zookeeper.server.quorum.FastLeaderElection - Sending
> Notification: 3 (n.leader), 0x0 (n.zxid), 0x1 (n.round), 3 (recipient), 0
> (myid), 0x2 (n.peerEpoch)
> 2012-03-14 16:23:12,776 13309 [WorkerSender[myid=0]] DEBUG
> org.apache.zookeeper.server.quorum.QuorumCnxManager - There is a connection
> already for server 3
> 2012-03-14 16:23:12,776 13309 [QuorumPeer[myid=0]/127.0.0.1:2900] DEBUG
> org.apache.zookeeper.server.quorum.FastLeaderElection - Sending
> Notification: 3 (n.leader), 0x0 (n.zxid), 0x1 (n.round), 4 (recipient), 0
> (myid), 0x2 (n.peerEpoch)
> 2012-03-14 16:23:12,776 13309 [WorkerSender[myid=0]] DEBUG
> org.apache.zookeeper.server.quorum.QuorumCnxManager - There is a connection
> already for server 4
> 2012-03-14 16:23:12,776 13309 [WorkerReceiver[myid=0]] DEBUG
> org.apache.zookeeper.server.quorum.FastLeaderElection - Receive new
> notification message. My id = 0
> 2012-03-14 16:23:12,776 13309 [WorkerReceiver[myid=0]] INFO
> org.apache.zookeeper.server.quorum.FastLeaderElection - Notification: 4
> (n.leader), 0x0 (n.zxid), 0x1 (n.round), LOOKING (n.state), 1 (n.sid), 0x0
> (n.peerEPoch), LOOKING (my state)
> 2012-03-14 16:23:12,776 13309 [WorkerReceiver[myid=0]] DEBUG
> org.apache.zookeeper.server.quorum.FastLeaderElection - Receive new
> notification message. My id = 0
> 2012-03-14 16:23:12,776 13309 [WorkerReceiver[myid=0]] INFO
> org.apache.zookeeper.server.quorum.FastLeaderElection - Notification: 3
> (n.leader), 0x0 (n.zxid), 0x1 (n.round), LOOKING (n.state), 2 (n.sid), 0x2
> (n.peerEPoch), LOOKING (my state)
> 2012-03-14 16:23:12,776 13309 [QuorumPeer[myid=0]/127.0.0.1:2900] DEBUG
> org.apache.zookeeper.server.quorum.FastLeaderElection - Adding vote: from=1,
> proposed leader=3, proposed zxid=0x0, proposed election epoch=0x1
> 2012-03-14 16:23:12,776 13309 [QuorumPeer[myid=0]/127.0.0.1:2900] DEBUG
> org.apache.zookeeper.server.quorum.FastLeaderElection - id: 3, proposed id:
> 3, zxid: 0x0, proposed zxid: 0x0
> 2012-03-14 16:23:12,776 13309 [QuorumPeer[myid=0]/127.0.0.1:2900] DEBUG
> org.apache.zookeeper.server.quorum.FastLeaderElection - id: 3, proposed id:
> 3, zxid: 0x0, proposed zxid: 0x0
> 2012-03-14 16:23:12,776 13309 [QuorumPeer[myid=0]/127.0.0.1:2900] DEBUG
> org.apache.zookeeper.server.quorum.FastLeaderElection - id: 3, proposed id:
> 3, zxid: 0x0, proposed zxid: 0x0
> 2012-03-14 16:23:12,776 13309 [QuorumPeer[myid=0]/127.0.0.1:2900] DEBUG
> org.apache.zookeeper.server.quorum.FastLeaderElection - id: 4, proposed id:
> 3, zxid: 0x0, proposed zxid: 0x0
> 2012-03-14 16:23:12,776 13309 [QuorumPeer[myid=0]/127.0.0.1:2900] DEBUG
> org.apache.zookeeper.server.quorum.FastLeaderElection - id: 4, proposed id:
> 3, zxid: 0x0, proposed zxid: 0x0
> {noformat}
> I'm guessing this means that nodes 3 and 4 are fighting over leadership, but
> I don't know enough about the leader election code to debug this any further.
> Attaching a tarball with the logs for each run and the data directories for
> each node (though I don't think any data is being written to ZK during the
> test).
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