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Date: Fri, 8 Jun 2012 04:35:23 +0000 (UTC)
From: "Hadoop QA (JIRA)" <jira@apache.org>
To: hdfs-issues@hadoop.apache.org
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Subject: [jira] [Commented] (HDFS-3492) fix some misuses of InputStream#skip
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    [ https://issues.apache.org/jira/browse/HDFS-3492?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13291543#comment-13291543 ] 

Hadoop QA commented on HDFS-3492:
---------------------------------

-1 overall.  Here are the results of testing the latest attachment 
  http://issues.apache.org/jira/secure/attachment/12531333/HDFS-3492.002.patch
  against trunk revision .

    +1 @author.  The patch does not contain any @author tags.

    +1 tests included.  The patch appears to include 2 new or modified test files.

    +1 javac.  The applied patch does not increase the total number of javac compiler warnings.

    +1 javadoc.  The javadoc tool did not generate any warning messages.

    +1 eclipse:eclipse.  The patch built with eclipse:eclipse.

    +1 findbugs.  The patch does not introduce any new Findbugs (version 1.3.9) warnings.

    +1 release audit.  The applied patch does not increase the total number of release audit warnings.

    -1 core tests.  The patch failed these unit tests in hadoop-hdfs-project/hadoop-hdfs hadoop-hdfs-project/hadoop-hdfs-httpfs:

                  org.apache.hadoop.hdfs.server.namenode.metrics.TestNameNodeMetrics
                  org.apache.hadoop.hdfs.server.datanode.TestBPOfferService
                  org.apache.hadoop.test.TestHFSTestCase
                  org.apache.hadoop.test.TestHTestCase

    +1 contrib tests.  The patch passed contrib unit tests.

Test results: https://builds.apache.org/job/PreCommit-HDFS-Build/2617//testReport/
Console output: https://builds.apache.org/job/PreCommit-HDFS-Build/2617//console

This message is automatically generated.
                
> fix some misuses of InputStream#skip
> ------------------------------------
>
>                 Key: HDFS-3492
>                 URL: https://issues.apache.org/jira/browse/HDFS-3492
>             Project: Hadoop HDFS
>          Issue Type: Bug
>            Reporter: Colin Patrick McCabe
>            Assignee: Colin Patrick McCabe
>            Priority: Minor
>         Attachments: HDFS-3492.001.patch, HDFS-3492.002.patch
>
>
> It seems that we have a few cases where programmers are calling InputStream#skip and not handling "short skips."  Unfortunately, the skip method is documented and implemented so that it doesn't actually skip the requested number of bytes, but simply tries to skip at most that amount of bytes.  A better name probably would have been trySkip or similar.
> It seems like most of the time when the argument to skip is small enough, we'll succeed almost all of the time.  This is no doubt an implementation artifact of some of the popular stream implementations.  This tends to hide the bug-- however, it is still waiting to emerge at some point if those implementations ever change or if buffer sizes are adjusted, etc.
> All of these cases can be fixed by calling IOUtils#skipFully to get the behavior that the programmer expects-- i.e., skipping by the specified amount.

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