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https://issues.apache.org/jira/browse/HAMA-521?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13239386#comment-13239386
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Suraj Menon commented on HAMA-521:
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We can get duplicate messages even with today's design. Receiver should know if
the messages it has received has any duplicates. So if the receiver got
messages from both original and its recovered task. There should be a way the
receiver could filter out the duplicate messages. However this is a part of the
solution of HAMA-440 ;). So hope we can take a decision while we commit for the
purpose. Let's ignore the fault tolerance part from this issue now.
> Improve message buffering to save memory
> ----------------------------------------
>
> Key: HAMA-521
> URL: https://issues.apache.org/jira/browse/HAMA-521
> Project: Hama
> Issue Type: Sub-task
> Reporter: Thomas Jungblut
> Assignee: Thomas Jungblut
> Attachments: HAMA-521.patch, HAMA-521_1.patch
>
>
> Suraj and I had a bit of discussion about incoming and outgoing message
> buffering and scalability.
> Currently everything lies on the heap, causing huge amounts of GC and waste
> of memory. We can do better.
> Therefore we need to extract an abstract Messenger class which is directly
> under the interface but over the compressor class.
> It should abstract the use of the queues in the back (currently lot of
> duplicated code) and it should be backed by a sequencefile on local disk.
> Once sync() starts it should return a message iterator for combining and then
> gets put into a message bundle which is send over RPC.
> On the other side we get a bundle and looping over it putting everything into
> the heap making it much larger than it needs to be. Here we can also flush on
> disk because we are just using a queue-like method to the user-side.
> Plus points:
> In case we have enough heap (see our new metric system), we can also
> implement a buffering technology that is not flushing everything to disk.
> Open questions:
> I don't know how much slower the whole system gets, but it would save alot of
> memory. Maybe we should first evaluate if it is really needed.
> In any case, the refactoring of the duplicate code in the messengers is
> needed.
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