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From "Todd Lipcon (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-7256) Resource leak during failure scenario of closing of resources.
Date Thu, 26 May 2011 18:05:49 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-7256?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13039840#comment-13039840

Todd Lipcon commented on HADOOP-7256:

- looks like there are some hard tabs, please configure your editor to use spaces per our
coding guidelines
- in the newly added LOG.debug line, please include some text. eg LOG.debug("Ignoring error
closing socket", ignored);
- in the test case, please add a fail("Didn't throw") line after the IOUtils.copyBytes call.
That will make sure that the exception is properly propagated and not swallowed.
- Probably better to separate the test in two -- one for the case where the inputstream throws,
and another for the case when the output stream throws.

> Resource leak during failure scenario of closing of resources. 
> ---------------------------------------------------------------
>                 Key: HADOOP-7256
>                 URL: https://issues.apache.org/jira/browse/HADOOP-7256
>             Project: Hadoop Common
>          Issue Type: Bug
>    Affects Versions: 0.20.2, 0.21.0
>            Reporter: ramkrishna.s.vasudevan
>            Priority: Minor
>             Fix For: 0.23.0
>         Attachments: HADOOP-7256-patch-1.patch
>   Original Estimate: 8h
>  Remaining Estimate: 8h
> Problem Statement:
> ===============
> There are chances of resource leak and stream not getting closed 
> Take the case when after copying data we try to close the Input and output stream followed
by closing of the socket.
> Suppose an exception occurs while closing the input stream(due to runtime exception)
then the subsequent operations of closing the output stream and socket may not happen and
there is a chance of resource leak.
> Scenario 
> =======
> During long run of map reduce jobs, the copyFromLocalFile() api is getting called.
> Here we found some exceptions happening. As a result of this we found the lsof value
raising leading to resource leak.
> Solution:
> =======
> While doing a close operation of any resource catch the RuntimeException also rather
than catching the IOException alone.
> Additionally there are places where we try to close a resource in the catch block.
> If this close fails, we just throw and come out of the current flow.
> In order to avoid this, we can carry out the close operation in the finally block.
> Probable reasons for getting RunTimeExceptions:
> =====================================
> We may get runtime exception from customised hadoop streams like FSDataOutputStream.close()
. So better to handle RunTimeExceptions also.

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