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https://issues.apache.org/jira/browse/GIRAPH-250?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13416999#comment-13416999
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Alessandro Presta commented on GIRAPH-250:
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Good idea to use hashing here. Are you getting a good distribution across the
whole list or mainly avoiding collisions on the first split?
If you use the number of workers and some sort of incremental worker id (I'm
not familiar, but maybe WorkerInfo#getPartitionId()?), you may even be
deterministic and assign equally-spaced starting points to the workers, and see
how it performs.
Either way, this already sounds like a good improvement!
Can't comment on the wait interval, if 10 seconds gives you better results on a
few different scenarios, then it's probably sensible.
> Let workers contending for InputSplits during INPUT_SUPERSTEP guess better,
> choose quicker.
> -------------------------------------------------------------------------------------------
>
> Key: GIRAPH-250
> URL: https://issues.apache.org/jira/browse/GIRAPH-250
> Project: Giraph
> Issue Type: Improvement
> Components: bsp, graph, zookeeper
> Affects Versions: 0.2.0
> Reporter: Eli Reisman
> Assignee: Eli Reisman
> Priority: Minor
> Fix For: 0.2.0
>
> Attachments: GIRAPH-250-1.patch, GIRAPH-250-2.patch
>
>
> In the job logs it has become clear that workers trying to scan for
> master-created Znodes indicating an InputSplit is available to claim (and
> read) are starting very similar lists of znode names to scan (iterating from
> 0 through the list all at the same time)
> what you see in the logs is lots of misses, followed by finally a hit
> somewhere. By using iterating the list, but starting from a different spot
> for each worker (see the patch its a simple change using the hash code of the
> worker hostname + index and mod that by the size of the list of possible
> splits to claim) we (mostly) iterate starting from different parts of the
> input split list each worker gets, thereby lowering contention dramatically
> and ensuring everyone will more quickly claim (at least their first) input
> split. This seems to work very well so far.
> passes mvn verify etc.
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