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From "Jothi Padmanabhan (JIRA)" <j...@apache.org>
Subject [jira] Updated: (HADOOP-4664) Parallelize job initialization
Date Thu, 05 Mar 2009 07:23:56 GMT

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

Jothi Padmanabhan updated HADOOP-4664:
--------------------------------------

    Attachment: hadoop-4664-v2.patch

Attaching a patch that changes JobHistory.openJobs to a concurrenthashmap

> 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: Jothi Padmanabhan
>            Priority: Blocker
>             Fix For: 0.20.0
>
>         Attachments: hadoop-4664-v1.patch, hadoop-4664-v2.patch, 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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