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https://issues.apache.org/jira/browse/KAFKA-4277?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16543436#comment-16543436
]
ASF GitHub Bot commented on KAFKA-4277:
---------------------------------------
Sh4pe opened a new pull request #5365: Don't throw exceptions in
KafkaHealthcheck.handleNewSession. Should fix KAFKA-4277
URL: https://github.com/apache/kafka/pull/5365
### Problem we've encountered
We've had a problem recently with Kafka brokers that apparently did not
work. The last remarkable message we found in our logs was
[this](https://github.com/apache/kafka/blob/1.0/core/src/main/scala/kafka/utils/ZkUtils.scala#L440)
Exception, which contained
[KafkaHealthcheck.register()](https://github.com/apache/kafka/blob/1.0/core/src/main/scala/kafka/server/KafkaHealthcheck.scala#L59)
in its stack trace.
In our case, the ephemeral Zookeeper node for the broker that
[handleNewSession](https://github.com/apache/kafka/blob/1.0/core/src/main/scala/kafka/server/KafkaHealthcheck.scala#L119)
should create apparently still existed - Kafka restarted too quickly after it
crashed before. The exception caused by the attempt to re-create this Zookeeper
node eventually causes
[ZkEventThread.run()](https://github.com/sgroschupf/zkclient/blob/0.9/src/main/java/org/I0Itec/zkclient/ZkEventThread.java#L63)
to idle, since the Exception is caught there and merely logged. Since no
further Events occur, the event thread apparently idles.
### Solution and rationale
In order to have clean well-defined behavior in this case, we've decided
that it would be best to finish the broker process in such a case. We've
decided to `sys.exit(1)` and rely on the
[shutdownHook](https://github.com/apache/kafka/blob/1.0/core/src/main/scala/kafka/Kafka.scala#L88)
to do a proper shutdown.
This pull request contains the change described above.
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> 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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