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Date: Wed, 28 Sep 2016 21:38:20 +0000 (UTC)
From: "Daniel Templeton (JIRA)" <jira@apache.org>
To: yarn-issues@hadoop.apache.org
Message-ID: <JIRA.13008318.1475085217000.691869.1475098700595@Atlassian.JIRA>
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Subject: [jira] [Commented] (YARN-5685) Non-embedded HA failover is broken
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archived-at: Wed, 28 Sep 2016 21:38:22 -0000


    [ https://issues.apache.org/jira/browse/YARN-5685?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15530951#comment-15530951 ] 

Daniel Templeton commented on YARN-5685:
----------------------------------------

I think I finally get it.  The net is that HA now requires either Curator or embedded to be enabled.  Letting the {{ZKRMStateStore}} handle the RM state transitions is no longer an option and hasn't been for a while.  There are only three ways {{transitionToActive()}} gets called:

# {{EmbeddedElectorService.becomeActive()}} -- embedded failover
# {{LeaderElectorService.isLeader()}} -- curator failover
# {{AdminService.transitionToActive()}} -- CLI

The question is what to do about non-embedded failover.  I don't think it's worth making non-embedded failover work again.  I think we're better off declaring non-embedded failover to be dead and removing the option altogether.

Given that this has been broken for a while and no one has noticed, I'm going to bump the priority down a bit.

> Non-embedded HA failover is broken
> ----------------------------------
>
>                 Key: YARN-5685
>                 URL: https://issues.apache.org/jira/browse/YARN-5685
>             Project: Hadoop YARN
>          Issue Type: Bug
>          Components: resourcemanager
>    Affects Versions: 2.9.0, 3.0.0-alpha1
>            Reporter: Daniel Templeton
>            Assignee: Daniel Templeton
>            Priority: Critical
>
> YARN-4559 broke RM HA when embedded automatic failover is disabled.  The {{ZKRMStateStore}} will now only start its monitoring thread when automatic failover not enabled (which is patently useless).  I presume the intended change was to have the monitoring thread started when automatic failover is not *embedded*.
> If HA is enabled with automatic failover enabled and embedded failover disabled, all RMs all come up in standby state.  To make one of them active, the {{--forcemanual}} flag must be used when manually triggering the state change.  Should the active go down, the standby will not become active and must be manually transitioned with the {{--forcemanual}} flag.


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