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From "Andrew Purtell (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-6721) RegionServer Group based Assignment
Date Mon, 05 Nov 2012 17:10:15 GMT

    [ https://issues.apache.org/jira/browse/HBASE-6721?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13490741#comment-13490741

Andrew Purtell commented on HBASE-6721:

Looks like the HBASE-6721_94_2 patch contains the patch on HBASE-7042 too?

MasterExec and MasterExecResult are still in the HBASE-6721_94_2 patch, please use Exec and
ExecResult and remove MasterExec and MasterExecResult and the change to HbaseObjectWritable.

bq. moved storage of group information from hdfs to zookeeper

Nice, this moves forward in the right direction IMHO. However, I don't see where this information
is persisted into a table. Did I miss it? Because HBase state in ZooKeeper can be cleared
by administrators in some recovery scenarios, we can't consider it persistent storage. See
how the security coprocessor handles this.

bq. This stuff should all be pulled out into a separate package that can be put into a Maven
module like done with security in 0.94.
Isn't that a bit too much overhead? 

The patch adds group-based assignment coprocessor specific classes to the main Master package
and the main Client package. I should clarify that I didn't say your work must be put into
a separate Maven module, but rather coprocessors are mini-applications, and should be organized
as such. It is important to keep this set of changes, distinct optional functionality, grouped
together apart from unrelated core code. Why not {{org.apache.hadoop.hbase.client.group}}
and {{org.apache.hadoop.hbase.master.group}} etc.? I hope this feedback is clearer now. 

bq. What changes to core code remain after that?
I've updated the patch, there should be minimal and no invasive changes.

Thanks! Much better.

Still some possible whitepsace issues though, the patch may contain mixed tabs and spaces?
Some of the formatting looks off when I view it. If you are using Eclipse, we have a HBase
formatter in dev-support/ now that may be helpful. 

> RegionServer Group based Assignment
> -----------------------------------
>                 Key: HBASE-6721
>                 URL: https://issues.apache.org/jira/browse/HBASE-6721
>             Project: HBase
>          Issue Type: New Feature
>            Reporter: Francis Liu
>            Assignee: Vandana Ayyalasomayajula
>             Fix For: 0.96.0
>         Attachments: HBASE-6721_94_2.patch, HBASE-6721_94.patch, HBASE-6721_94.patch,
> In multi-tenant deployments of HBase, it is likely that a RegionServer will be serving
out regions from a number of different tables owned by various client applications. Being
able to group a subset of running RegionServers and assign specific tables to it, provides
a client application a level of isolation and resource allocation.
> The proposal essentially is to have an AssignmentManager which is aware of RegionServer
groups and assigns tables to region servers based on groupings. Load balancing will occur
on a per group basis as well. 
> This is essentially a simplification of the approach taken in HBASE-4120. See attached

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