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https://issues.apache.org/jira/browse/MAPREDUCE-1266?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12788349#action_12788349
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Todd Lipcon commented on MAPREDUCE-1266:
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bq. If so should we just set the minimum lower to 1.5s or 2s and get it over
with?
Sure, I'm happy to not add the conf knob. I'd say we should set the minimum to
0.5s - a localhost ping every 0.5 seconds is negligible on modern machines.
> 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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