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From "Alex Liu (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-5544) Hadoop jobs assigns only one mapper in task
Date Tue, 28 May 2013 20:21:20 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-5544?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13668633#comment-13668633
] 

Alex Liu commented on CASSANDRA-5544:
-------------------------------------

CassandraColumnInputFormat define the split size, so we don't want Pig to override it by combining
splits. We can always tune the split size to tune the performance. Next step, we can open
up a little bit so that Pig user can specify split size configuration.

Vnode hadoop performance generally decreases, we can do the split combination at Cassandra
side to improve the performance, which could be another ticket.
                
> Hadoop jobs assigns only one mapper in task 
> --------------------------------------------
>
>                 Key: CASSANDRA-5544
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-5544
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Hadoop
>    Affects Versions: 1.2.1
>         Environment: Red hat linux 5.4, Hadoop 1.0.3, pig 0.11.1
>            Reporter: Shamim Ahmed
>            Assignee: Alex Liu
>         Attachments: 5544.txt, Screen Shot 2013-05-26 at 4.49.48 PM.png
>
>
> We have got very strange beheviour of hadoop cluster after upgrading 
> Cassandra from 1.1.5 to Cassandra 1.2.1. We have 5 nodes cluster of Cassandra, where
three of them are hodoop slaves. Now when we are submitting job through Pig script, only one
map assigns in task running on one of the hadoop slaves regardless of 
> volume of data (already tried with more than million rows).
> Configure of pig as follows:
> export PIG_HOME=/oracle/pig-0.10.0
> export PIG_CONF_DIR=${HADOOP_HOME}/conf
> export PIG_INITIAL_ADDRESS=192.168.157.103
> export PIG_RPC_PORT=9160
> export PIG_PARTITIONER=org.apache.cassandra.dht.Murmur3Partitioner
> Also we have these following properties in hadoop:
>  <property>
>  <name>mapred.tasktracker.map.tasks.maximum</name>
>  <value>10</value>
>  </property>
>  <property>
>  <name>mapred.map.tasks</name>
>  <value>4</value>
>  </property>

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