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From "Amar Kamat (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-2175) Blacklisted hosts may not be able to serve map outputs
Date Sat, 22 Mar 2008 12:33:24 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-2175?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12581264#action_12581264

Amar Kamat commented on HADOOP-2175:

 am not clear why you have the check in JobInProgress for doing lostTaskTracker outside the
bq. Also, inside lostTaskTracker you check for whether the task was already FAILED/KILLED
I did that because the TIP failed/killed before the TT got lost, should be kept failed/kiiled.
There is no need to reschedule or change their status. Since the task was not killed because
of lost TT, I ignored it.
bq. On the change to MiniMRCluster ....
I think there is a problem with MiniMRCluster w.r.t lost TTs. It keeps on trying for the TT
to be idle and eventually the test times out. I am still trying to find out why the MiniMR
gets stuck.
bq. On the TestLostBlackListedTracker, i don't think you need to make it that complicated
 The way you get events is also not very reliable w.r.t timing. In the first call to getTaskCompletionEvents,
you might get events.length = 0
I use launchJob which waits for the job to complete. Its a blocking call. 

> 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
>         Attachments: HADOOP-2175-v1.1.patch, HADOOP-2175-v1.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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