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

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

zhihai xu created HADOOP-12189:
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             Summary: 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
    Affects Versions: 2.7.1
            Reporter: zhihai xu
            Assignee: zhihai xu


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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