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From "Christian Rolf (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-6665) Batching in CqlRecordWriter
Date Fri, 07 Feb 2014 09:47:19 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-6665?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13894348#comment-13894348
] 

Christian Rolf commented on CASSANDRA-6665:
-------------------------------------------

Thanks for the quick feedback John! 
The biggest issue we've seen is on larger rings, where the write tasks quickly run out of
heap (caching is per replica). That's why I left the batching disabled by default.

> Batching in CqlRecordWriter
> ---------------------------
>
>                 Key: CASSANDRA-6665
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-6665
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Hadoop
>         Environment: Cluster of 12 nodes, each node with 256-384 vnodes. RPC threads
capped at 2048.
>            Reporter: Christian Rolf
>            Priority: Minor
>         Attachments: batchWrite.txt
>
>
> We're writing from Pig map tasks, about 20 million records of one integer each. 
> For the case of 12 nodes, with 256-384 vnodes per node, we get around 4000 threads per
mapper. This obviously overloads the nodes, since the number of RPC threads are capped, and
the write fails. 
> Also, each transfer is only in the order of a few bytes of payload. Clearly batching
is a good solution.



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