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https://issues.apache.org/jira/browse/KAFKA-2572?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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John Firth updated KAFKA-2572:
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Summary: zk connection instability (was: zk connection instability,
perhaps precipitated by zk client timeout during rebalance)
> zk connection instability
> -------------------------
>
> Key: KAFKA-2572
> URL: https://issues.apache.org/jira/browse/KAFKA-2572
> Project: Kafka
> Issue Type: Bug
> Components: zkclient
> Affects Versions: 0.8.2.1
> Environment: zk version 3.4.6,
> CentOS 6, 2.6.32-504.1.3.el6.x86_64
> Reporter: John Firth
> Attachments: 090815-digest.log, 090815-full.log, 091115-digest.log,
> 091115-full.log.zip
>
>
> On two occasions, have seen zk session expiry, followed by a timeout during a
> consumer rebalance following this expiry, followed by multiple successive zk
> session expiries. Restarting the process using the zk client resolved the
> problems.
> Comparing these with a case in which a new stable zk session was created
> following a session expiry, the timeout during rebalance is not seen in the
> successful case.
> This behavior was seen on 09/08 and 09/11 -- the attached 'full' logs show
> all logs entries minus entries particular to our application. For 09/08, the
> time span is 2015-09-08T12:52:06.069-04:00 to 2015-09-08T13:14:48.250-04:00;
> for 11/08, the time span is between 2015-09-11T01:38:17.000-04:00 to
> 2015-09-11T07:44:47.124-04:00. The digest logs are the result of retaining
> only error and warning entries, and entries containing any of: "begin
> rebalancing", "end rebalancing", "timed", and "zookeeper state". For the
> 09/11 digest logs, entries from the kafka.network.Processor logger are also
> excised for clarity. Unfortunately, debug logging was not enabled during
> these events.
> The 09/08 case is a little more straightforward than the 09/11 case. In the
> 09/08 case, a session times out at 2015-09-08T12:52:06.069-04:00; two
> timeouts for the same session are then seen during the rebalance that follows
> the establishment of that session, at 2015-09-08T12:52:19.107-04:00 and
> 2015-09-08T12:52:31.639-04:00. The rebalance begins at
> 2015-09-08T12:52:06.667-04:00. The connection to ZK then expires and is
> restablished multiple times before the process is killed after
> 2015-09-08T13:13:41.655-04:00, which marks the last entry in the digest.
> The 09/11 case shows repeated cycles of session expiry, followed by
> rebalancing activity, followed by a pause during which nothing is heard from
> the zk server, followed by a session timeout.
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