[jira] [Commented] (HADOOP-12189) CallQueueManager may drop elements from the queue sometimes when calling swapQueue

["zhihai xu (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HADOOP-12189?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14614495#comment-14614495 ] 

zhihai xu commented on HADOOP-12189:
------------------------------------

I uploaded a patch HADOOP-12189.000.patch for review. This patch will wait for the threads blocked by {{CallQueueManager#put}} in swapQueue, so it will make sure all the elements from old queue added by these blocked threads are processed.

> CallQueueManager may drop elements from the queue sometimes when calling swapQueue
> ----------------------------------------------------------------------------------
>
>                 Key: HADOOP-12189
>                 URL: https://issues.apache.org/jira/browse/HADOOP-12189
>             Project: Hadoop Common
>          Issue Type: Bug
>          Components: ipc, test
>    Affects Versions: 2.7.1
>            Reporter: zhihai xu
>            Assignee: zhihai xu
>         Attachments: HADOOP-12189.000.patch
>
>
> CallQueueManager may drop elements from the queue sometimes when calling {{swapQueue}}. 
> The following test failure 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.



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