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https://issues.apache.org/jira/browse/YARN-1029?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13850942#comment-13850942
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Karthik Kambatla commented on YARN-1029:
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bq. I dont quite agree with the ZKFCProtocol being added to the AdminService.
The RM should have only 1 interface for HA related commands to be sent to it.
That interface is the HAServiceProtocol. External ZKFC or embedded elector or
the cluster admin. All of them should have the same entry point to the RM. I
dont think the RM should setup different protocols for the embedded elector
case.
If I have to sum up the two protocols,
# HAServiceProtocol is to perform HA-related operations on one master (NN/ RM)
that concern only that master: transition *this master* to active, standby or
what is *this master*'s status, health?
# ZKFCProtocol is HA-related operations on one master that concern multiple
masters: failover from one master to the other, cede being active (while ceding
from leader election). My understanding is that - ZKFCProtocol is *not specific
to ZKFC*. In fact, it might even make sense to merge this with the
HAServiceProtocol given that we want all HA implementations to handle
multiple-master interactions.
That said, given how the common code is currently laid out, even though it
appears the AdminService is implementing multiple protocols for HA, the
AdminService should handle the functionalities of both protocols. No?
> Allow embedding leader election into the RM
> -------------------------------------------
>
> Key: YARN-1029
> URL: https://issues.apache.org/jira/browse/YARN-1029
> Project: Hadoop YARN
> Issue Type: Sub-task
> Reporter: Bikas Saha
> Assignee: Karthik Kambatla
> Attachments: embedded-zkfc-approach.patch, yarn-1029-0.patch,
> yarn-1029-0.patch, yarn-1029-approach.patch
>
>
> It should be possible to embed common ActiveStandyElector into the RM such
> that ZooKeeper based leader election and notification is in-built. In
> conjunction with a ZK state store, this configuration will be a simple
> deployment option.
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