[
https://issues.apache.org/jira/browse/HADOOP-12189?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14639568#comment-14639568
]
zhihai xu commented on HADOOP-12189:
------------------------------------
Thanks Chris and Arpit for reviewing! thanks Andrew for reviewing and
committing the patch!
> Improve CallQueueManager#swapQueue to make queue elements drop nearly
> impossible.
> ---------------------------------------------------------------------------------
>
> Key: HADOOP-12189
> URL: https://issues.apache.org/jira/browse/HADOOP-12189
> Project: Hadoop Common
> Issue Type: Improvement
> Components: ipc, test
> Affects Versions: 2.7.1
> Reporter: zhihai xu
> Assignee: zhihai xu
> Fix For: 2.8.0
>
> Attachments: HADOOP-12189.000.patch, HADOOP-12189.001.patch,
> HADOOP-12189.none_guarantee.000.patch, HADOOP-12189.none_guarantee.001.patch,
> HADOOP-12189.none_guarantee.002.patch
>
>
> Improve CallQueueManager#swapQueue to make queue elements drop nearly
> impossible. This is the trade-off between performance and functionality, even
> in the very very rare situation, we may drop one element, but it is not the
> end of the world since the client may still recover with timeout.
> CallQueueManager may drop elements from the queue sometimes when calling
> {{swapQueue}}.
> The following test failure from TestCallQueueManager shown some elements in
> the queue are dropped.
> https://builds.apache.org/job/PreCommit-HADOOP-Build/7150/testReport/org.apache.hadoop.ipc/TestCallQueueManager/testSwapUnderContention/
> {code}
> java.lang.AssertionError: expected:<27241> but was:<27245>
> at org.junit.Assert.fail(Assert.java:88)
> at org.junit.Assert.failNotEquals(Assert.java:743)
> at org.junit.Assert.assertEquals(Assert.java:118)
> at org.junit.Assert.assertEquals(Assert.java:555)
> at org.junit.Assert.assertEquals(Assert.java:542)
> at
> org.apache.hadoop.ipc.TestCallQueueManager.testSwapUnderContention(TestCallQueueManager.java:220)
> {code}
> It looked like the elements in the queue are dropped due to
> {{CallQueueManager#swapQueue}}
> Looked at the implementation of {{CallQueueManager#swapQueue}}, there is a
> possibility that the elements in the queue are dropped. If the queue is full,
> the calling thread for {{CallQueueManager#put}} is blocked for long time. It
> may put the element into the old queue after queue in {{takeRef}} is changed
> by swapQueue, then this element in the old queue will be dropped.
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
