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From "Nigel Daley (JIRA)" <j...@apache.org>
Subject [jira] Updated: (HADOOP-2752) ability to configure gap/lag parameters for speculative execution for maps/reduces
Date Fri, 01 Feb 2008 18:31:08 GMT

     [ https://issues.apache.org/jira/browse/HADOOP-2752?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Nigel Daley updated HADOOP-2752:
--------------------------------

    Fix Version/s:     (was: 0.16.0)

Removing from 0.16.0 release as this is not a blocker

> ability to configure gap/lag parameters for speculative execution for maps/reduces
> ----------------------------------------------------------------------------------
>
>                 Key: HADOOP-2752
>                 URL: https://issues.apache.org/jira/browse/HADOOP-2752
>             Project: Hadoop Core
>          Issue Type: New Feature
>          Components: mapred
>    Affects Versions: 0.15.3
>            Reporter: Joydeep Sen Sarma
>
> Motivation is obvious:
> - sometimes reduces have side-effects - but maps don't (for example reduces compute something
and write it somewhere)
> - want to turn ON speculative for maps (because maps are usually way less expensive.
map progress counters are reliable etc.) - but OFF for reduces (very expensive to run two
reducers instead of one).
> It's also likely that in future you may want different setting for speculative triggers
for maps and reduces ... (but that's a different issue).
> I will submit a patch (since we are putting this into effect on our cluster - and it
seems simple enough :-)).

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