[jira] [Commented] (HAMA-521) Improve message buffering to save memory

["ChiaHung Lin (Commented) (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HAMA-521?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13238487#comment-13238487 ] 

ChiaHung Lin commented on HAMA-521:
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MemoryQueue is similar to the original way by storing messages in LinkedList that looks ok.

Regarding to memory footprint, how if storing messages remotely e.g. hdfs or spilling messages to the target server? Or storing in e.g. memcache may be an option. 

Each has its own pros and cons. Storing remote allows messages available, but may be slow; spilled messages may lost if the target server fails, but speed may be increased because of local read; memcache may increase dependency/ overhead in lots of setup, etc.
                
> 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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