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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 19:44:50 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-2926?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12574704#action_12574704
] 

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

> Then shouldn't we use it, instead of using IOUtils.closeStream() at all?

May be. I am not sure if we should enforce it every where. IMHO the readability becomes really
bad when lot of streams are involved as in DataNode (2 sockets and their input out streams,
and two file channels).



> 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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