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From "Sameer Paranjpye (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-2175) Blacklisted hosts may not be able to serve map outputs
Date Wed, 26 Mar 2008 18:03:29 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-2175?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12582376#action_12582376
] 

Sameer Paranjpye commented on HADOOP-2175:
------------------------------------------

Let's not confuse lost and blacklisted tasktrackers. A lost tasktracker is one that doesn't
check in with the JT and a tasktracker blacklisted for a job is one that causes tasks to fail
for that job and they need to be handled very differently.

We should move this issue to 0.18. We don't have a coherent model for task failures, the blacklisting
logic is already messy and adding half a dozen if statements will only make it messier.


> Blacklisted hosts may not be able to serve map outputs
> ------------------------------------------------------
>
>                 Key: HADOOP-2175
>                 URL: https://issues.apache.org/jira/browse/HADOOP-2175
>             Project: Hadoop Core
>          Issue Type: Bug
>          Components: mapred
>            Reporter: Runping Qi
>            Assignee: Amar Kamat
>             Fix For: 0.18.0
>
>         Attachments: HADOOP-2175-v1.1.patch, HADOOP-2175-v1.patch, HADOOP-2175-v2.patch,
HADOOP-2175-v2.patch
>
>
> After a node fails 4 mappers (tasks), it is added to blacklist thus it will no longer
accept tasks.
> But, it will continue serve the map outputs of any mappers that ran successfully there.

> However, the node may not be able serve the map outputs either. 
> This will cause the reducers to mark the corresponding map outputs as from slow hosts,

> but continue to try to get the map outputs from that node.
> This may lead to waiting forever.

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