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From "Raghu Angadi (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-2926) Ignoring IOExceptions on close
Date Mon, 03 Mar 2008 18:38:50 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-2926?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12574657#action_12574657
] 

Raghu Angadi commented on HADOOP-2926:
--------------------------------------

You are right. The example above shows wrong use of closeStream(). 

> it clear it can only be used after the write operation has failed and is being cleaned
up.
But this is not true. Many times this used to close sockets where socket needs to be closed
because of unrelated error (say i/o failed on a different stream).


> Ignoring IOExceptions on close
> ------------------------------
>
>                 Key: HADOOP-2926
>                 URL: https://issues.apache.org/jira/browse/HADOOP-2926
>             Project: Hadoop Core
>          Issue Type: Bug
>          Components: dfs
>    Affects Versions: 0.16.0
>            Reporter: Owen O'Malley
>            Assignee: dhruba borthakur
>            Priority: Critical
>             Fix For: 0.16.1
>
>
> Currently in HDFS there are a lot of calls to IOUtils.closeStream that are from finally
blocks. I'm worried that this can lead to data corruption in the file system. Take the first
instance in DataNode.copyBlock: it writes the block and then calls closeStream on the output
stream. If there is an error at the end of the file that is detected in the close, it will
be *completely* ignored. Note that logging the error is not enough, the error should be thrown
so that the client knows the failure happened.
> {code}
>    try {
>      file1.write(...);
>      file2.write(...);
>    } finally {
>       IOUtils.closeStream(file);
>   }
> {code}
> is *bad*. It must be rewritten as:
> {code}
>    try {
>      file1.write(...);
>      file2.write(...);
>      file1.close(...);
>      file2.close(...);
>    } catch (IOException ie) {
>      IOUtils.closeStream(file1);
>      IOUtils.closeStream(file2);
>      throw ie;
>    }
> {code}
> I also think that IOUtils.closeStream should be renamed IOUtils.cleanupFailedStream or
something to make it clear it can only be used after the write operation has failed and is
being cleaned up.

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