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From "Chris Li (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-12189) CallQueueManager may drop elements from the queue sometimes when calling swapQueue
Date Thu, 09 Jul 2015 20:10:05 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-12189?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14621175#comment-14621175

Chris Li commented on HADOOP-12189:

Great, couple more minor things:

Can we update the comment for queueReallyIsEmpty, and also include how the constants CHECKPOINT_INTERVAL_MS
and CHECKPOINT_NUM come into play? 

What do you think about expressing the code in a for loop? Makes the code more readable I

private boolean queueIsReallyEmpty(BlockingQueue<?> q) {
  for (int i = 0; i < CHECKPOINT_NUM; i++) {
    if (!q.isEmpty()) {
      return false;

    try {
    } catch (InterruptedException ie) {
      return false;

  return true;


> 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, HADOOP-12189.001.patch, HADOOP-12189.none_guarantee.000.patch,
> 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.

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