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https://issues.apache.org/jira/browse/ZOOKEEPER-3399?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16848259#comment-16848259
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Enrico Olivelli commented on ZOOKEEPER-3399:
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{quote}
Recently we have moved some of our production clusters to the top of the trunk
{quote}
This is encouraging !
I think it is time to think to cut a release for 3.6.0
> Remove logging in getGlobalOutstandingLimit for optimal performance.
> --------------------------------------------------------------------
>
> Key: ZOOKEEPER-3399
> URL: https://issues.apache.org/jira/browse/ZOOKEEPER-3399
> Project: ZooKeeper
> Issue Type: Bug
> Components: server
> Affects Versions: 3.6.0
> Reporter: Michael Han
> Assignee: Michael Han
> Priority: Major
> Labels: pull-request-available
> Fix For: 3.6.0
>
> Time Spent: 1h
> Remaining Estimate: 0h
>
> Recently we have moved some of our production clusters to the top of the
> trunk. One issue we found is a performance regression on read and write
> latency on the clusters where the quorum is also serving traffic. The average
> read latency increased by 50x, p99 read latency increased by 300x.
> The root cause is a log statement introduced in ZOOKEEPER-3177 (PR711), where
> we added a LOG.info statement in getGlobalOutstandingLimit.
> getGlobalOutstandingLimit is on the critical code path for request processing
> and for each request, it will be called twice (one at processing the packet,
> one at finalizing the request response). This not only degrades performance
> of the server, but also bloated the log file, when the QPS of a server is
> high.
> This only impacts clusters when the quorum (leader + follower) is serving
> traffic. For clusters where only observers are serving traffic no impact is
> observed.
>
>
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