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https://issues.apache.org/jira/browse/MAPREDUCE-1266?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12786552#action_12786552
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Arun C Murthy commented on MAPREDUCE-1266:
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It takes ~1s for the map/reduce task JVM to come up...
I'm failing to see how sub-second heartbeat intervals will help.
> 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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