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From "Eli Reisman (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (GIRAPH-322) Run Length Encoding for Vertex#sendMessageToAllEdges might curb out of control message growth in large scale jobs
Date Mon, 29 Oct 2012 22:23:12 GMT

    [ https://issues.apache.org/jira/browse/GIRAPH-322?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13486431#comment-13486431
] 

Eli Reisman commented on GIRAPH-322:
------------------------------------

I am waiting to see how the message passing plumbing shapes up so I don't get in the way of
that, then we can deal with ideas around this if they need to be dealt with at all at that
point. The purpose of 322 is message deduplication when we know it can be done (as in broadcast
messaging from the vertex API) so if there's a need, I'll come back to this.

If this is one of the JIRA issues holding up the new release, we can resolve it won't fix
and I'll post a fresh JIRA someday.

                
> Run Length Encoding for Vertex#sendMessageToAllEdges might curb out of control message
growth in large scale jobs
> -----------------------------------------------------------------------------------------------------------------
>
>                 Key: GIRAPH-322
>                 URL: https://issues.apache.org/jira/browse/GIRAPH-322
>             Project: Giraph
>          Issue Type: Improvement
>          Components: bsp
>    Affects Versions: 0.2.0
>            Reporter: Eli Reisman
>            Assignee: Eli Reisman
>            Priority: Minor
>             Fix For: 0.2.0
>
>         Attachments: GIRAPH-322-1.patch, GIRAPH-322-2.patch, GIRAPH-322-3.patch, GIRAPH-322-4.patch,
GIRAPH-322-5.patch, GIRAPH-322-6.patch
>
>
> Vertex#sendMessageToAllEdges is a case that goes against the grain of the data structures
and code paths used to transport messages through a Giraph application and out on the network.
While messages to a single vertex can be combined (and should be) in some applications that
could make use of this broadcast messaging, the out of control message growth of algorithms
like triangle closing means we need to de-duplicate messages bound for many vertices/partitions.
> This will be an evolving solution (this first patch is just the first step) and currently
it does not present a robust solution for disk-spill message stores. I figure I can get some
advice about that or it can be a follow-up JIRA if this turns out to be a fruitful pursuit.
This first patch is also Netty-only and simply defaults to the old sendMessagesToAllEdges()
implementation if USE_NETTY is false. All this can be cleaned up when we know this works and/or
is worth pursuing.
> The idea is to send as few broadcast messages as possible by run-length encoding their
delivery and only duplicating message on the network when they are bound for different partitions.
This is also best when combined with "-Dhash.userPartitionCount=# of workers" so you don't
do too much of that.
> If this shows promise I will report back and keep working on this. As it is, it represents
an end-to-end solution, using Netty, for in-memory messaging. It won't break with spill to
disk, but you do lose the de-duplicating effect.
> More to follow, comments/ideas welcome. I expect this to change a lot as I test it and
ideas/suggestions crop up.

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