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From "Ted Yu (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-3813) Change RPC callQueue size from "handlerCount * MAX_QUEUE_SIZE_PER_HANDLER;"
Date Sun, 08 May 2011 13:49:03 GMT

    [ https://issues.apache.org/jira/browse/HBASE-3813?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13030485#comment-13030485
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Ted Yu commented on HBASE-3813:
-------------------------------

BlockingQueue has remainingCapacity() that returns the number of additional elements that
this queue can ideally (in the absence of memory or resource constraints) accept without blocking.
Maybe we should write an implementation of BlockingQueue that is aware of the sizes of the
objects it holds. Meaning it would block if the next element to be queued would cause total
estimated heap consumed to exceed pre-determined threshold.

I wonder if we should add variant of HbaseObjectWritable.readObject() that records the size
of the Object returned.


> Change RPC callQueue size from "handlerCount * MAX_QUEUE_SIZE_PER_HANDLER;"
> ---------------------------------------------------------------------------
>
>                 Key: HBASE-3813
>                 URL: https://issues.apache.org/jira/browse/HBASE-3813
>             Project: HBase
>          Issue Type: Bug
>    Affects Versions: 0.92.0
>            Reporter: stack
>            Priority: Critical
>         Attachments: 3813.txt
>
>
> Yesterday debugging w/ Jack we noticed that with few handlers on a big box, he was seeing
stats like this:
> {code}
> 2011-04-21 11:54:49,451 DEBUG org.apache.hadoop.ipc.HBaseServer: Server connection from
X.X.X.X:60931; # active connections: 11; # queued calls: 2500
> {code}
> We had 2500 items in the rpc queue waiting to be processed.
> Turns out he had too few handlers for number of clients (but also, it seems like he figured
hw issues in that his RAM bus was running at 1/4 the rate that it should have been running
at).
> Chatting w/ J-D this morning, he asked if the queues hold 'data'.  The queues hold 'Calls'.
 Calls are the client request.  They contain data.
> Jack had 2500 items queued.  If each item to insert was 1MB, thats 25k * 1MB of memory
that is outside of our generally accounting.
> Currently the queue size is handlers * MAX_QUEUE_SIZE_PER_HANDLER where MAX_QUEUE_SIZE_PER_HANDLER
is hardcoded to be 100.
> If the queue is full we block (LinkedBlockingQueue).
> Going to change the queue size from 100 to 10 by default -- but also will make it configurable
and will doc. this as possible cause of OOME.  Will try it on production here before committing
patch.

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