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https://issues.apache.org/jira/browse/ZOOKEEPER-3320?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16796844#comment-16796844
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Igor Skokov commented on ZOOKEEPER-3320:
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??I would expect an issue in QuorumCnxManager to bring the peer down if it
cannot create the socket but it seems this only occurs with a BindException and
not a generic SocketException. At the least, I think we ought to fix that.??
As I can see, QuorumCnxManager.Listener.run() catches IOException, and
consequently SocketException&BindException. In any case, ZK server will
continue to run without leader election participation:)
??Looking at this from the opposite direction, can you add the desired delay in
the startup sequence of your Kubernetes container? My concern is that the
pattern of "DNS is currently unreliable but will be reliable soon" seems
specific to the container management and may result in strange behavior when
applied to other environments.??
Sure, I can integrate artificial delay to my container(or some DNS name check
loop).
But, it will be great if ZK can handle such temporary errors by itself. I
agree, that "retry forever" is not best solution, but as I mention earlier,
maybe we can make retry count configurable?
> 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.
> Maybe, if leader election halts, we should abort process.
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