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https://issues.apache.org/jira/browse/KAFKA-1451?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14064976#comment-14064976
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Kenny commented on KAFKA-1451:
------------------------------
This can also be caused by restarting Kafka quickly after a sigkill. I had a
supervisord config file with 'stopwaitsecs=1' and it would pretty reliably
create a hung Kafka process.
> Broker stuck due to leader election race
> -----------------------------------------
>
> Key: KAFKA-1451
> URL: https://issues.apache.org/jira/browse/KAFKA-1451
> Project: Kafka
> Issue Type: Bug
> Components: core
> Affects Versions: 0.8.1.1
> Reporter: Maciek Makowski
> Priority: Minor
>
> h3. Symptoms
> The broker does not become available due to being stuck in an infinite loop
> while electing leader. This can be recognised by the following line being
> repeatedly written to server.log:
> {code}
> [2014-05-14 04:35:09,187] INFO I wrote this conflicted ephemeral node
> [{"version":1,"brokerid":1,"timestamp":"1400060079108"}] at /controller a
> while back in a different session, hence I will backoff for this node to be
> deleted by Zookeeper and retry (kafka.utils.ZkUtils$)
> {code}
> h3. Steps to Reproduce
> In a single kafka 0.8.1.1 node, single zookeeper 3.4.6 (but will likely
> behave the same with the ZK version included in Kafka distribution) node
> setup:
> # start both zookeeper and kafka (in any order)
> # stop zookeeper
> # stop kafka
> # start kafka
> # start zookeeper
> h3. Likely Cause
> {{ZookeeperLeaderElector}} subscribes to data changes on startup, and then
> triggers an election. if the deletion of ephemeral {{/controller}} node
> associated with previous zookeeper session of the broker happens after
> subscription to changes in new session, election will be invoked twice, once
> from {{startup}} and once from {{handleDataDeleted}}:
> * {{startup}}: acquire {{controllerLock}}
> * {{startup}}: subscribe to data changes
> * zookeeper: delete {{/controller}} since the session that created it timed
> out
> * {{handleDataDeleted}}: {{/controller}} was deleted
> * {{handleDataDeleted}}: wait on {{controllerLock}}
> * {{startup}}: elect -- writes {{/controller}}
> * {{startup}}: release {{controllerLock}}
> * {{handleDataDeleted}}: acquire {{controllerLock}}
> * {{handleDataDeleted}}: elect -- attempts to write {{/controller}} and then
> gets into infinite loop as a result of conflict
> {{createEphemeralPathExpectConflictHandleZKBug}} assumes that the existing
> znode was written from different session, which is not true in this case; it
> was written from the same session. That adds to the confusion.
> h3. Suggested Fix
> In {{ZookeeperLeaderElector.startup}} first run {{elect}} and then subscribe
> to data changes.
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