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https://issues.apache.org/jira/browse/MAPREDUCE-1266?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12787296#action_12787296
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Todd Lipcon commented on MAPREDUCE-1266:
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That's actually not my blog post, I just came about it the other day and
figured he had a good point.
Regarding idle vs "heavy job load", again, this is not going to be an
improvement for any real clusters. Its only purpose is making
pseudo-distributed or other "too small for real work" clusters a bit more
responsive.
Are there any substantive reasons against this? I didn't anticipate much
discussion over a change in a single constant that only affects tiny clusters :)
> Allow heartbeat interval smaller than 3 seconds for tiny clusters
> -----------------------------------------------------------------
>
> Key: MAPREDUCE-1266
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-1266
> Project: Hadoop Map/Reduce
> Issue Type: Improvement
> Components: jobtracker, task, tasktracker
> Affects Versions: 0.22.0
> Reporter: Todd Lipcon
> Priority: Minor
>
> For small clusters, the heartbeat interval has a large effect on job latency.
> This is especially true on pseudo-distributed or other "tiny" (<5 nodes)
> clusters. It's not a big deal for production, but new users would have a
> happier first experience if Hadoop seemed snappier.
> I'd like to change the minimum heartbeat interval from 3.0 seconds to perhaps
> 0.5 seconds (but have it governed by an undocumented config parameter in case
> people don't like this change). The cluster size-based ramp up of interval
> will maintain the current scalable behavior for large clusters with no
> negative effect.
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