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From "Todd Lipcon (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-2702) A single failed name dir can cause the NN to exit
Date Mon, 19 Dec 2011 21:05:30 GMT

    [ https://issues.apache.org/jira/browse/HDFS-2702?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13172612#comment-13172612

Todd Lipcon commented on HDFS-2702:

I think the addendum is correct. I wish we had a fault injection point for each of these cases,
but that's a larger amount of work... something like how we use ErrorSimulator for errors
in checkpoints would be great.
> A single failed name dir can cause the NN to exit 
> --------------------------------------------------
>                 Key: HDFS-2702
>                 URL: https://issues.apache.org/jira/browse/HDFS-2702
>             Project: Hadoop HDFS
>          Issue Type: Bug
>    Affects Versions: 1.0.0
>            Reporter: Eli Collins
>            Assignee: Eli Collins
>            Priority: Critical
>         Attachments: hdfs-2702.txt, hdfs-2702.txt, hdfs-2702.txt, hdfs-2702.txt, hdfs-2702.txt
> There's a bug in FSEditLog#rollEditLog which results in the NN process exiting if a single
name dir has failed. Here's the relevant code:
> {code}
> close()  // So editStreams.size() is 0 
> foreach edits dir {
>   ..
>   eStream = new ...  // Might get an IOE here
>   editStreams.add(eStream);
> } catch (IOException ioe) {
>   removeEditsForStorageDir(sd);  // exits if editStreams.size() <= 1  
> }
> {code}
> If we get an IOException before we've added two edits streams to the list we'll exit,
eg if there's an error processing the 1st name dir we'll exit even if there are 4 valid name
dirs. The fix is to move the checking out of removeEditsForStorageDir (nee processIOError)
or modify it so it can be disabled in some cases, eg here where we don't yet know how many
streams are valid.

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