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https://issues.apache.org/jira/browse/HBASE-12498?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14234561#comment-14234561
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stack commented on HBASE-12498:
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I like it that master continues to tell regionservers what they should serve.
Thanks [~amitanand]
> Integrate HydraBase RMap in RegionManager
> -----------------------------------------
>
> Key: HBASE-12498
> URL: https://issues.apache.org/jira/browse/HBASE-12498
> Project: HBase
> Issue Type: Sub-task
> Components: master, Region Assignment
> Reporter: Rishit Shroff
> Assignee: Amitanand Aiyer
>
> We need to integrate the idea of RMap (Global Region Locator) into HBase.
> RMap:
> In Hydrabase, we wanted to avoid having special tables that require to be
> online and available, before other servers can start processing their
> regions. To this end, in hydrabase, we use a notion of RMap — that tells the
> servers which regions to open; and also servers as a look up place for the
> clients to discover the set of servers handling a particular region.
> This RMap is stored in a well known path, as specified in the configuration.
> Upon initialization, RegionServers read this file and determine the set of
> regions that it needs to open; and the set of peers that it expects to hear
> from for each of those regions.
> Since RMap is stored in HDFS, the only way to change it is to create a new
> HDFS file and update the servers about it. This is intended to be a
> not-so-common operation; however, this may be required when a new machine
> joins the service, or an existing machine needs to be taken away for a
> significant amount of time to perform maintenance.
> We run a daemon, every 15 minutes, (currently in the master) to determine the
> set of machines going to repair and vice versa; and update the RMap
> accordingly.
> 1. In the current hydraBase model, updating the RMap is done by a single
> daemon; while every region server individually reads and updates itself
> accordingly.
> 2. OSS HBase seems to be using a model where a dedicated master/server
> manager is responsible for coordinating the regions that should be
> opened/served by each region server. Region servers simply follow the
> instructions received from the server manager.
> With respect to integrating both. We plan to use the servermanager to read
> the RMap and coordinate the region opens on various regionservers. RMap will
> be still stored as a HDFS file, that will be read by the ServerManager/Master
> to assign regions.
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