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From "Andrey Stepachev (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HBASE-12035) Client does an RPC to master everytime a region is relocated
Date Fri, 23 Jan 2015 17:07:35 GMT

     [ https://issues.apache.org/jira/browse/HBASE-12035?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

Andrey Stepachev updated HBASE-12035:
    Attachment: HBASE-12035.patch

First attempt to move master out of read/whatever path.
With this patch I introduce new column family to META. This family contains table information
like state and htabledescriptor.
That looks like { tableName -> state: TableState, descriptor: HTableDescriptor } stored
in separate column family. That has great advantage:
1. Old clients would not break, if they use correct column family in scans
2. We can extend this column family with other information if needed
3. Scans for all families return table row first.

How that works:
1. I have wrapped TableDescriptors with MetaBackedTableDescriptors, that is simple proxy that
intersepts all updates of descriptors and copy them to META after they been modified in hfds.
2. Right after meta onlined master runs sync and updates META with information from hdfs.

Here is still need to be added some fault tolerance, but basically that could work well (we
don't remove master RPC for table states, we can use strict queries still if needed, so META
here can be used with a sense of 'eventually' consistent data, because primary data stored
in hdfs).

[~enis], [~stack], can you look at that? Let's clean up the mess I introduced with moving
states from zk :)
(sorry, was away, relocated to new country, had no time to do things)
Thank you.

> Client does an RPC to master everytime a region is relocated
> ------------------------------------------------------------
>                 Key: HBASE-12035
>                 URL: https://issues.apache.org/jira/browse/HBASE-12035
>             Project: HBase
>          Issue Type: Improvement
>            Reporter: Enis Soztutar
>            Assignee: Andrey Stepachev
>            Priority: Critical
>             Fix For: 2.0.0
>         Attachments: HBASE-12035.patch
> HBASE-7767 moved table enabled|disabled state to be kept in hdfs instead of zookeeper.
isTableDisabled() which is used in HConnectionImplementation.relocateRegion() now became a
master RPC call rather than a zookeeper client call. Since we do relocateRegion() calls everytime
we want to relocate a region (region moved, RS down, etc) this implies that when the master
is down, the some of the clients for uncached regions will be affected. 
> See HBASE-7767 and HBASE-11974 for some more background. 

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