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From "Jothi Padmanabhan (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-3327) Shuffling fetchers waited too long between map output fetch re-tries
Date Wed, 21 Jan 2009 05:23:59 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-3327?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12665705#action_12665705

Jothi Padmanabhan commented on HADOOP-3327:

Looks good. A few points
* Some comments on the changes in the code would be good.
* The percentages that we use to decide maxNotifications and fetchRetriesPerMap should be
* Since fetchRetriesPerMap is computed during every iteration as per the current copiedMapOutputs.size,
it is possible that we might delay a notification to the JT by one failure. For example, consider
maxFetchRetriesPerMap = 5 and numRetries=4. During the next failure numRetries = 5, and let
us say we cross the threshold and reset fetchRetriesperMap = 2 (5/2). As per the existing
logic, we would have sent a notification as  numRetires = maxFetchRetriesPerMap. But with
the new logic, we will wait as 5%2 != 0. But this is a corner case and probably can be overlooked.

> Shuffling fetchers waited too long between map output fetch re-tries
> --------------------------------------------------------------------
>                 Key: HADOOP-3327
>                 URL: https://issues.apache.org/jira/browse/HADOOP-3327
>             Project: Hadoop Core
>          Issue Type: Bug
>          Components: mapred
>            Reporter: Runping Qi
>            Assignee: Amareshwari Sriramadasu
>             Fix For: 0.21.0
>         Attachments: hadoop-3327-v1.patch, hadoop-3327-v2.patch, hadoop-3327-v3.patch,
hadoop-3327.patch, patch-3327.txt

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