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https://issues.apache.org/jira/browse/HBASE-2357?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13048710#comment-13048710
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Andrew Purtell commented on HBASE-2357:
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CP Endpoints operate over HBase RPC.
bq. Sounds like the basic design is there are N slaves that connect to one
master using a socket based protocol. There will be a socket connection open
per-region per slave.
That is not how HBase RPC works. One connection between the endpoints (in this
case regionserver and regionserver) is established upon demand, reaped when
idle too long, and multiplexed over in the meantime.
bq. The Coprocessor will place edits into a per region queue
And spill the queues under heap pressure presumably. Or give up on a too laggy
slave and have it killed to avoid blowing out heap in the alternative.
bq. Or should it function in the HMaster?
No we need to think of the HMaster as always on the verge of going away to be
supplanted by ZooKeeper mediated distributed actions.
> Coprocessors: Add read-only region replicas (slaves) for availability and
> fast region recovery
> ----------------------------------------------------------------------------------------------
>
> Key: HBASE-2357
> URL: https://issues.apache.org/jira/browse/HBASE-2357
> Project: HBase
> Issue Type: Sub-task
> Components: master, regionserver
> Reporter: Todd Lipcon
> Assignee: Andrew Purtell
>
> I dont plan on working on this in the short term, but the idea is to extend
> region ownership to have two modes. Each region has one primary region server
> and N slave region servers. The slaves would follow the master (probably by
> streaming the relevant HLog entries directly from it) and be able to serve
> stale reads. The benefit is twofold: (a) provides the ability to spread read
> load, (b) enables very fast region failover/rebalance since the memstore is
> already nearly up to date on the slave RS.
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