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https://issues.apache.org/jira/browse/KAFKA-4277?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16366546#comment-16366546
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Jun Rao commented on KAFKA-4277:
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[~nico.meyer], do you know if the conflicting ephemeral node was there
temporarily or permanently? From the ZK server commit log, was there any
indication that the ephemeral node was removed after session expiration, and if
so, when?
> creating ephemeral node already exist
> -------------------------------------
>
> Key: KAFKA-4277
> URL: https://issues.apache.org/jira/browse/KAFKA-4277
> Project: Kafka
> Issue Type: Bug
> Affects Versions: 0.10.0.0
> Reporter: Feixiang Yan
> Priority: Major
>
> I use zookeeper 3.4.6.
> Zookeeper session time out, zkClient try reconnect failed. Then re-establish
> the session and re-registering broker info in ZK, throws NODEEXISTS Exception.
> I think it is because the ephemeral node which created by old session has
> not removed.
> I read the
> [ZkUtils.scala|https://github.com/apache/kafka/blob/0.8.1/core/src/main/scala/kafka/utils/ZkUtils.scala]
> of 0.8.1, createEphemeralPathExpectConflictHandleZKBug try create node in a
> while loop until create success. This can solve the issue. But in
> [ZkUtils.scala|https://github.com/apache/kafka/blob/0.10.0.1/core/src/main/scala/kafka/utils/ZkUtils.scala]
> 0.10.1 the function removed.
> {noformat}
> [2016-10-07 19:00:32,562] INFO Socket connection established to
> 10.191.155.238/10.191.155.238:21819, initiating session
> (org.apache.zookeeper.ClientCnxn)
> [2016-10-07 19:00:32,563] INFO zookeeper state changed (Expired)
> (org.I0Itec.zkclient.ZkClient)
> [2016-10-07 19:00:32,564] INFO Unable to reconnect to ZooKeeper service,
> session 0x1576b11f9b201bd has expired, closing socket connection
> (org.apache.zookeeper.ClientCnxn)
> [2016-10-07 19:00:32,564] INFO Initiating client connection,
> connectString=10.191.155.237:21819,10.191.155.238:21819,10.191.155.239:21819/cluster2
> sessionTimeout=6000 watcher=org.I0Itec.zkclient.ZkClient@ae71be2
> (org.apache.zookeeper.ZooKeeper)
> [2016-10-07 19:00:32,566] INFO Opening socket connection to server
> 10.191.155.237/10.191.155.237:21819. Will not attempt to authenticate using
> SASL (unknown error) (org.apache.zookeeper.ClientCnxn)
> [2016-10-07 19:00:32,566] INFO Socket connection established to
> 10.191.155.237/10.191.155.237:21819, initiating session
> (org.apache.zookeeper.ClientCnxn)
> [2016-10-07 19:00:32,566] INFO EventThread shut down
> (org.apache.zookeeper.ClientCnxn)
> [2016-10-07 19:00:32,567] INFO Session establishment complete on server
> 10.191.155.237/10.191.155.237:21819, sessionid = 0x1579ecd39c20006,
> negotiated timeout = 6000 (org.apache.zookeeper.ClientCnxn)
> [2016-10-07 19:00:32,567] INFO zookeeper state changed (SyncConnected)
> (org.I0Itec.zkclient.ZkClient)
> [2016-10-07 19:00:32,608] INFO re-registering broker info in ZK for broker 3
> (kafka.server.KafkaHealthcheck$SessionExpireListener)
> [2016-10-07 19:00:32,610] INFO Creating /brokers/ids/3 (is it secure? false)
> (kafka.utils.ZKCheckedEphemeral)
> [2016-10-07 19:00:32,611] INFO Result of znode creation is: NODEEXISTS
> (kafka.utils.ZKCheckedEphemeral)
> [2016-10-07 19:00:32,614] ERROR Error handling event ZkEvent[New session
> event sent to kafka.server.KafkaHealthcheck$SessionExpireListener@324f1bc]
> (org.I0Itec.zkclient.ZkEventThread)
> java.lang.RuntimeException: A broker is already registered on the path
> /brokers/ids/3. This probably indicates that you either have configured a
> brokerid that is already in use, or else you have shutdown this broker and
> restarted it faster than the zookeeper timeout so it appears to be
> re-registering.
> at kafka.utils.ZkUtils.registerBrokerInZk(ZkUtils.scala:305)
> at kafka.utils.ZkUtils.registerBrokerInZk(ZkUtils.scala:291)
> at kafka.server.KafkaHealthcheck.register(KafkaHealthcheck.scala:70)
> at
> kafka.server.KafkaHealthcheck$SessionExpireListener.handleNewSession(KafkaHealthcheck.scala:104)
> at org.I0Itec.zkclient.ZkClient$6.run(ZkClient.java:735)
> at org.I0Itec.zkclient.ZkEventThread.run(ZkEventThread.java:71)
> {noformat}
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