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https://issues.apache.org/jira/browse/KAFKA-1441?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Guozhang Wang resolved KAFKA-1441.
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Resolution: Fixed
> Purgatory purge causes latency spikes
> -------------------------------------
>
> Key: KAFKA-1441
> URL: https://issues.apache.org/jira/browse/KAFKA-1441
> Project: Kafka
> Issue Type: Bug
> Reporter: Jay Kreps
>
> The request purgatory has a funky thing where it periodically loops over all
> watches and purges them. If you have a fair number of partitions you can
> accumulate lots of watches and purging them can take a long time. During this
> time all expiry is halted.
> Here is an example log:
> [2014-05-08 21:07:41,950] INFO ExpiredRequestReaper-2 Expired request after
> 10ms: 5829 (kafka.server.RequestPurgatory$ExpiredRequestReaper)
> [2014-05-08 21:07:41,952] INFO ExpiredRequestReaper-2 Expired request after
> 10ms: 5882 (kafka.server.RequestPurgatory$ExpiredRequestReaper)
> [2014-05-08 21:07:41,967] INFO ExpiredRequestReaper-2 Expired request after
> 11ms: 5884 (kafka.server.RequestPurgatory$ExpiredRequestReaper)
> [2014-05-08 21:07:41,968] INFO ExpiredRequestReaper-2 Purging purgatory
> (kafka.server.RequestPurgatory$ExpiredRequestReaper)
> [2014-05-08 21:07:41,969] INFO ExpiredRequestReaper-2 Purged 0 requests from
> delay queue. (kafka.server.RequestPurgatory$ExpiredRequestReaper)
> [2014-05-08 21:07:42,305] INFO ExpiredRequestReaper-2 Purged 340809 (watcher)
> requests. (kafka.server.RequestPurgatory$ExpiredRequestReaper)
> [2014-05-08 21:07:42,305] INFO ExpiredRequestReaper-2 Expired request after
> 106ms: 5847 (kafka.server.RequestPurgatory$ExpiredRequestReaper)
> [2014-05-08 21:07:42,305] INFO ExpiredRequestReaper-2 Expired request after
> 106ms: 5904 (kafka.server.RequestPurgatory$ExpiredRequestReaper)
> [2014-05-08 21:07:42,328] INFO ExpiredRequestReaper-2 Expired request after
> 10ms: 5908 (kafka.server.RequestPurgatory$ExpiredRequestReaper)
> [2014-05-08 21:07:42,329] INFO ExpiredRequestReaper-2 Expired request after
> 10ms: 5852 (kafka.server.RequestPurgatory$ExpiredRequestReaper)
> [2014-05-08 21:07:42,343] INFO ExpiredRequestReaper-2 Expired request after
> 11ms: 5854 (kafka.server.RequestPurgatory$ExpiredRequestReaper)
> Combined with our buggy purgatory request impls that can sometimes hit their
> expiration this can lead to huge latency spikes.
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