[jira] [Updated] (KAFKA-1387) Kafka getting stuck creating ephemeral node it has already created when two zookeeper sessions are established in a very short period of time

["Flavio Junqueira (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/KAFKA-1387?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Flavio Junqueira updated KAFKA-1387:
------------------------------------
    Fix Version/s: 0.8.3

> Kafka getting stuck creating ephemeral node it has already created when two zookeeper sessions are established in a very short period of time
> ---------------------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: KAFKA-1387
>                 URL: https://issues.apache.org/jira/browse/KAFKA-1387
>             Project: Kafka
>          Issue Type: Bug
>    Affects Versions: 0.8.1.1
>            Reporter: Fedor Korotkiy
>            Assignee: Flavio Junqueira
>            Priority: Blocker
>              Labels: newbie, patch, zkclient-problems
>             Fix For: 0.8.3
>
>         Attachments: KAFKA-1387.patch, kafka-1387.patch
>
>
> Kafka broker re-registers itself in zookeeper every time handleNewSession() callback is invoked.
> https://github.com/apache/kafka/blob/0.8.1/core/src/main/scala/kafka/server/KafkaHealthcheck.scala 
> Now imagine the following sequence of events.
> 1) Zookeeper session reestablishes. handleNewSession() callback is queued by the zkClient, but not invoked yet.
> 2) Zookeeper session reestablishes again, queueing callback second time.
> 3) First callback is invoked, creating /broker/[id] ephemeral path.
> 4) Second callback is invoked and it tries to create /broker/[id] path using createEphemeralPathExpectConflictHandleZKBug() function. But the path is already exists, so createEphemeralPathExpectConflictHandleZKBug() is getting stuck in the infinite loop.
> Seems like controller election code have the same issue.
> I'am able to reproduce this issue on the 0.8.1 branch from github using the following configs.
> # zookeeper
> tickTime=10
> dataDir=/tmp/zk/
> clientPort=2101
> maxClientCnxns=0
> # kafka
> broker.id=1
> log.dir=/tmp/kafka
> zookeeper.connect=localhost:2101
> zookeeper.connection.timeout.ms=100
> zookeeper.sessiontimeout.ms=100
> Just start kafka and zookeeper and then pause zookeeper several times using Ctrl-Z.



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