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From "Eli Collins (JIRA)" <j...@apache.org>
Subject [jira] Updated: (MAPREDUCE-1213) TaskTrackers restart is very slow because it deletes distributed cache directory synchronously
Date Thu, 02 Sep 2010 04:57:56 GMT

     [ https://issues.apache.org/jira/browse/MAPREDUCE-1213?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Eli Collins updated MAPREDUCE-1213:
-----------------------------------

    Hadoop Flags: [Incompatible change, Reviewed]  (was: [Reviewed])
    Release Note: Directories specified in mapred.local.dir that can not be created now cause
the TaskTracker to fail to start.

Marking as in incompatible change as mapred.local.dirs that do not exist are no longer with
this change. You'll get the following error and the TT will not start.

ERROR org.apache.hadoop.mapred.TaskTracker: Can not start task tracker because java.io.IOException:
Cannot create toBeDeleted in /doesNotExist



> TaskTrackers restart is very slow because it deletes distributed cache directory synchronously
> ----------------------------------------------------------------------------------------------
>
>                 Key: MAPREDUCE-1213
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-1213
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>    Affects Versions: 0.20.1
>            Reporter: dhruba borthakur
>            Assignee: Zheng Shao
>             Fix For: 0.21.0
>
>         Attachments: MAPREDUCE-1213.1.patch, MAPREDUCE-1213.2.patch, MAPREDUCE-1213.3.patch,
MAPREDUCE-1213.4.patch, MAPREDUCE-1213.branch-0.20.2.patch, MAPREDUCE-1213.branch-0.20.patch
>
>
> We are seeing that when we restart a tasktracker, it tries to recursively delete all
the file in the distributed cache. It invoked FileUtil.fullyDelete() which is very very slow.
This means that the TaskTracker cannot join the cluster for an extended period of time (upto
2 hours for us). The problem is acute if the number of files in a distributed cache is a few-thousands.

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