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https://issues.apache.org/jira/browse/MAPREDUCE-5110?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13617104#comment-13617104
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Karthik Kambatla commented on MAPREDUCE-5110:
---------------------------------------------

To answer Arun's question in its entirety: Yes, it reverts MAPREDUCE-2217. 
MAPREDUCE-2217 was to address the case of hung TaskTracker. Till the time of 
this JIRA, we never observed the current issue of the TT taking too long to 
start a task (which only seems to manifest due to hardware issues). The current 
approach handles both scenarios.
                
> Long task launch delays can lead to multiple parallel attempts of the task
> --------------------------------------------------------------------------
>
>                 Key: MAPREDUCE-5110
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-5110
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>          Components: tasktracker
>    Affects Versions: 1.1.2
>            Reporter: Karthik Kambatla
>            Assignee: Karthik Kambatla
>         Attachments: expose-mr-5110.patch, mr-5110.patch, mr-5110.patch
>
>
> If a task takes too long to launch, the JT expires the task and schedules 
> another attempt. The earlier attempt can start after the later attempt 
> leading to two parallel attempts running at the same time. This is 
> particularly an issue if the user turns off speculation and expects a single 
> attempt of a task to run at any point in time.

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