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From "David Bowen (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-1077) Race condition in fetching map outputs (might lead to hung reduces)
Date Wed, 07 Mar 2007 18:26:24 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-1077?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12478836

David Bowen commented on HADOOP-1077:

It is nice to see a patch with such good comments!

At the risk of being a coding-style bore, here are a couple of very minor suggestions: (1)
long synchronized blocks are a bit hard to read given the two-space indentation style - it
may be preferable to break them out into separate methods; (2) some may disagree, but I see
no need to write method arguments like "new Integer(loc.getMapId())" when you can now write
just "loc.getMapId()" and the compiler will automatically do the conversion.

> Race condition in fetching map outputs (might lead to hung reduces)
> -------------------------------------------------------------------
>                 Key: HADOOP-1077
>                 URL: https://issues.apache.org/jira/browse/HADOOP-1077
>             Project: Hadoop
>          Issue Type: Bug
>          Components: mapred
>            Reporter: Devaraj Das
>         Assigned To: Devaraj Das
>         Attachments: 1077.patch
> Sometimes when a map task is lost while the map-output fetch is happening from the TT
for that task, and the lost map has successfully executed on some other node, the event for
that successful execution is lost at the fetching TT. The fetching TT might eventually fail
to fetch the output for the lost task, but then since the event for the new run of the lost
map might also have been lost, the fetching TT might hang.
> This "hung" problem was discovered while working on HADOOP-1060.

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