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From "Eli Reisman (JIRA)" <>
Subject [jira] [Commented] (GIRAPH-322) Run Length Encoding for Vertex#sendMessageToAllEdges might curb out of control message growth in large scale jobs
Date Thu, 13 Sep 2012 17:50:07 GMT


Eli Reisman commented on GIRAPH-322:

The WorkerInfo is in reference to the fact that many are referenced needlessly inside PartitionOwners
in the messaging code to match everyone up with a Partition ID. One of the ways that worked
well in my experiments with this yesterday was to organize the messaging data structures around
WorkerInfos instead of PartitionOwners and use those to group related messages that could
be sent in a bundle together. The ClientRequestId would need to use a host/port hash from
WorkerInfo or something in place of a partitionId for sequencing but thats a small change.
This wouldn't be an amazing fix, but it would give us a finer-grained control over how we
bundle groups of messages between nodes and avoid extra data structures to route the messages
to partitions from the sending side. Anyway I'm thinking I shoudl put up a JIRA for this and
try it as a separate issue.

When the code died using my attempt at spill to disk, it died right at the beginning of the
run as soon as the graph data was loaded and the messaging started, same as without it. My
explanation from the previous comment is how the amortizing code died, sorry. Anyway from
your explanation it sounds like I did not have it set right if it was doing that. I am excited
to try it again.

> Run Length Encoding for Vertex#sendMessageToAllEdges might curb out of control message
growth in large scale jobs
> -----------------------------------------------------------------------------------------------------------------
>                 Key: GIRAPH-322
>                 URL:
>             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
> 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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