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Posted to dev@zookeeper.apache.org by "Igor Skokov (JIRA)" <ji...@apache.org> on 2019/03/17 08:29:00 UTC
[jira] [Updated] (ZOOKEEPER-3320) Leader election port stop listen
when hostname unresolvable for some time
[ https://issues.apache.org/jira/browse/ZOOKEEPER-3320?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Igor Skokov updated ZOOKEEPER-3320:
-----------------------------------
Summary: Leader election port stop listen when hostname unresolvable for some time (was: Don't give up on bind of leader election port)
> Leader election port stop listen when hostname unresolvable for some time
> --------------------------------------------------------------------------
>
> Key: ZOOKEEPER-3320
> URL: https://issues.apache.org/jira/browse/ZOOKEEPER-3320
> Project: ZooKeeper
> Issue Type: Bug
> Components: leaderElection
> Affects Versions: 3.4.10, 3.5.4
> Reporter: Igor Skokov
> Priority: Major
>
> When trying to run Zookeeper 3.5.4 cluster on Kubernetes, I found out that in some circumstances Zookeeper node stop listening on leader election port. This cause unavailability of ZK cluster.
> Zookeeper deployed as StatefulSet in term of Kubernetes and has following dynamic configuration:
> {code:java}
> zookeeper-0.zookeeper:2182:2183:participant;2181
> zookeeper-1.zookeeper:2182:2183:participant;2181
> zookeeper-2.zookeeper:2182:2183:participant;2181
> {code}
> Bind address contains DNS name which generated by Kubernetes for each StatefulSet pod.
> These DNS names will become resolvable after container start, but with some delay. That delay cause stopping of leader election port listener in QuorumCnxManager.Listener class.
> Error happens in QuorumCnxManager.Listener "run" method, it tries to bind leader election port to hostname which not resolvable at this moment. Retry count is hard-coded and equals to 3(with backoff of 1 sec).
> Zookeeper server log contains following errors:
> {code:java}
> 2019-03-17 07:56:04,844 [myid:1] - WARN [QuorumPeer[myid=1](plain=/0.0.0.0:2181)(secure=disabled):QuorumPeer@1230] - Unexpected exception
> java.net.SocketException: Unresolved address
> at java.base/java.net.ServerSocket.bind(ServerSocket.java:374)
> at java.base/java.net.ServerSocket.bind(ServerSocket.java:335)
> at org.apache.zookeeper.server.quorum.Leader.<init>(Leader.java:241)
> at org.apache.zookeeper.server.quorum.QuorumPeer.makeLeader(QuorumPeer.java:1023)
> at org.apache.zookeeper.server.quorum.QuorumPeer.run(QuorumPeer.java:1226)
> 2019-03-17 07:56:04,844 [myid:1] - WARN [QuorumPeer[myid=1](plain=/0.0.0.0:2181)(secure=disabled):QuorumPeer@1261] - PeerState set to LOOKING
> 2019-03-17 07:56:04,845 [myid:1] - INFO [QuorumPeer[myid=1](plain=/0.0.0.0:2181)(secure=disabled):QuorumPeer@1136] - LOOKING
> 2019-03-17 07:56:04,845 [myid:1] - INFO [QuorumPeer[myid=1](plain=/0.0.0.0:2181)(secure=disabled):FastLeaderElection@893] - New election. My id = 1, proposed zxid=0x0
> 2019-03-17 07:56:04,846 [myid:1] - INFO [WorkerReceiver[myid=1]:FastLeaderElection@687] - Notification: 2 (message format version), 1 (n.leader), 0x0 (n.zxid), 0xf (n.round), LOOKING (n.state), 1 (n.sid), 0x0 (n.peerEPoch), LOOKING (my state)0 (n.config version)
> 2019-03-17 07:56:04,979 [myid:1] - INFO [zookeeper-0.zookeeper:2183:QuorumCnxManager$Listener@892] - Leaving listener
> 2019-03-17 07:56:04,979 [myid:1] - ERROR [zookeeper-0.zookeeper:2183:QuorumCnxManager$Listener@894] - As I'm leaving the listener thread, I won't be able to participate in leader election any longer: zookeeper-0.zookeeper:2183
> {code}
> This error happens on most nodes on cluster start and Zookeeper is unable to form quorum. This will leave cluster in unusable state.
> As I can see, error present on branches 3.4 and 3.5.
> I think, this error can be fixed by configurable number of retries(instead of hard-coded value of 3).
> Other way to fix this is removing of max retries at all. Currently, ZK server only stop leader election listener and continue to serve on other ports. May be, if leader election halts, we should abort process.
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