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From "Andrew Purtell (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HBASE-2001) Coprocessors: Colocate arbitrary code with regions
Date Sat, 21 Nov 2009 19:36:40 GMT

    [ https://issues.apache.org/jira/browse/HBASE-2001?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12781036#action_12781036
] 

Andrew Purtell commented on HBASE-2001:
---------------------------------------

One application of this is like in process map reduce on the HBase cluster. Coprocessors accept
list of writables in and produce a list of writables out, like a mapper. Client library doing
collation and aggregation of per region invocations would be functionally like a reducer.


> Coprocessors: Colocate arbitrary code with regions
> --------------------------------------------------
>
>                 Key: HBASE-2001
>                 URL: https://issues.apache.org/jira/browse/HBASE-2001
>             Project: Hadoop HBase
>          Issue Type: Sub-task
>            Reporter: Andrew Purtell
>            Assignee: Andrew Purtell
>
> "Support arbitrary code that runs run next to each region in table. As regions split
and move, coprocessor code should automatically  move also."
> Use classloader which looks on HDFS.
> Associate a list of classes to load with each table. Put this in HRI so it inherits from
table but can be changed on a per region basis (so then those region specific changes can
inherited by daughters). 
> Not completely arbitrary code, should require implementation of an interface with callbacks
for:
> * Open
> * Close
> * Split
> * Compact
> * (Multi)get and scanner next()
> * (Multi)put
> * (Multi)delete
> Add method to HRegionInterface for invoking coprocessor methods and retrieving results.
 

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