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Date: Mon, 9 Nov 2015 21:14:11 +0000 (UTC)
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Subject: [jira] [Commented] (NIFI-1085) WebClusterManager starves immutable
 API requests under heavy load conditions
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    [ https://issues.apache.org/jira/browse/NIFI-1085?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14997369#comment-14997369 ] 

ASF subversion and git services commented on NIFI-1085:
-------------------------------------------------------

Commit 6add372bc142304ef25e0bafb49709654a995f08 in nifi's branch refs/heads/master from [~boardm26]
[ https://git-wip-us.apache.org/repos/asf?p=nifi.git;h=6add372 ]

NIFI-1085 WebClusterManager fair locking and HeartbeatMonitoringTimerTask scheduling


> WebClusterManager starves immutable API requests under heavy load conditions
> ----------------------------------------------------------------------------
>
>                 Key: NIFI-1085
>                 URL: https://issues.apache.org/jira/browse/NIFI-1085
>             Project: Apache NiFi
>          Issue Type: Improvement
>          Components: Core Framework
>    Affects Versions: 0.3.0
>            Reporter: Michael Moser
>             Fix For: 0.4.0
>
>
> With a 6 node cluster with thousands of components on the graph, we noticed that the ReentrantReadWriteLock in WebClusterManager can starve NiFi Web Server threads that are waiting on the read lock.
> Thread dumps shows the HeartbeatMonitoringTimerTask thread holding the write lock while many Web Server threads are parked waiting on the read lock.
> Modify the ReentrantReadWriteLock to operate in fair mode (to give the lock to threads waiting the longest, such as those wanting the read lock).
> Modify the HearbeatMonitoringTimerTask timer to not be scheduleAtFixedRate() but instead use schedule() to execute it less often if garbage collection blocks it.


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