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https://issues.apache.org/jira/browse/HBASE-2001?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12785368#action_12785368
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Andrew Purtell commented on HBASE-2001:
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.bq Would suggest that if coprocessors only need three states, then just do
those.
I'll make that clear in the documentation.
bq. First thought is that mimicing table interface might confuse more than it
helps but need to study more before I can offer stronger opinion.
There are two table interfaces currently:
1) PrivateStore -- a full table, private to the Coprocessor instance, backed by
a HFile+log
2) RegionAccessor -- a table interface to the region associated with the
Coprocessor, will reject edits outside the region, otherwise allows
(controlled) admin and mutation actions on the region. Also of note here the
Coprocessor hooks will be called for its own edits, just makes things easier.
Just FYI I have the environment implemented except for PrivateStore. No
classloader or ASM bits yet; I need to study and think more about that.
Meantime the next step is hooking up Coprocessors to the HRegion via calls out
to the interface in all the right places in HRegion, and possibly a few up in
HRegionServer.
> 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
> Attachments: asm-3.2-bin.zip, asm-transformations.pdf,
> org.apache.hadoop.hbase.HCoprocessor.java,
> org.apache.hadoop.hbase.HCoprocessor.pdf
>
>
> "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.
> Add methods in o.a.h.h.regionserver or subpackage which implement convenience
> functions for coprocessor methods and consistent/controlled access to
> internals: store access, threading, persistent and ephemeral state, scratch
> storage, etc.
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