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From "Hemanth Yamijala (JIRA)" <j...@apache.org>
Subject [jira] Updated: (HADOOP-4664) Parallelize job initialization
Date Fri, 27 Feb 2009 13:45:12 GMT

     [ https://issues.apache.org/jira/browse/HADOOP-4664?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Hemanth Yamijala updated HADOOP-4664:
-------------------------------------

         Priority: Blocker  (was: Major)
    Fix Version/s: 0.20.0

As per discussion in HADOOP-5286, we are trying to change the M/R design to not be affected
by a single slow data node. So, marking this a blocker for Hadoop 0.20. Matei, if it is acceptable,
Jothi has volunteered to take your patch forward, incorporating comments from Tom. Do you
have any objections to this ?

> Parallelize job initialization
> ------------------------------
>
>                 Key: HADOOP-4664
>                 URL: https://issues.apache.org/jira/browse/HADOOP-4664
>             Project: Hadoop Core
>          Issue Type: Improvement
>          Components: mapred
>            Reporter: Matei Zaharia
>            Assignee: Matei Zaharia
>            Priority: Blocker
>             Fix For: 0.20.0
>
>         Attachments: parallel-job-init-v1.patch
>
>
> The job init thread currently initializes one job at a time. However, this is a lengthy
and partly IO-bound process because all of the job's block locations need to be resolved through
the namenode and a map of them needs to be built. It can take tens of seconds. As a result,
the cluster sometimes initializes jobs too slowly for full utilization to be achieved, if
there are many small jobs queued up. It would be better to have a pool of threads that initialize
multiple jobs in parallel. One thing to be careful of, however, is not causing deadlocks or
holding locks for too long in these threads.

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