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https://issues.apache.org/jira/browse/HADOOP-14912?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Daryn Sharp updated HADOOP-14912:
---------------------------------
Attachment: HADOOP-14912.patch
Very simple patch to ensure an element is always extracted after a permit is
obtained. Basically change an if to while. Attempting to reproduce the race
with a test has proven futile (or it wouldn't have vexed me this long). The
issue has only been observed at scale.
> FairCallQueue may defer servicing calls
> ---------------------------------------
>
> Key: HADOOP-14912
> URL: https://issues.apache.org/jira/browse/HADOOP-14912
> Project: Hadoop Common
> Issue Type: Bug
> Components: ipc
> Affects Versions: 2.8.2
> Reporter: Daryn Sharp
> Assignee: Daryn Sharp
> Attachments: HADOOP-14912.patch
>
>
> HADOOP-14033 switched a lock to a semaphore to allow concurrency for
> producers & consumers to the underlying queues. A race condition was created
> that may cause a consumer to acquire a permit but not extract an element,
> leaving the semaphore with fewer permits than queued elements. This causes a
> minimum number of calls to always be present in the call queue.
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