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https://issues.apache.org/jira/browse/YARN-913?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14142090#comment-14142090
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Steve Loughran commented on YARN-913:
-------------------------------------

Oh, one more thing, that {{MicroZookeeperService}} which is used in tests? It's 
a YARN service-wrapped ZK microservice (based on Twill's test one), which can 
publish its ensemble information to registry clients running in-VM. This would 
make it straightforward to be deployed *inside* the RM ... in a small 1-2 node 
cluster it wouldn't be a load problem, and as the lifespan of the ZK == 
lifespan of RM, no worry about having a single ZK quorum outage impacting the 
RM.

I've not put the service under the RM. Someone is free to at some point in the 
future.

> Add a way to register long-lived services in a YARN cluster
> -----------------------------------------------------------
>
>                 Key: YARN-913
>                 URL: https://issues.apache.org/jira/browse/YARN-913
>             Project: Hadoop YARN
>          Issue Type: New Feature
>          Components: api, resourcemanager
>    Affects Versions: 2.5.0, 2.4.1
>            Reporter: Steve Loughran
>            Assignee: Steve Loughran
>         Attachments: 2014-09-03_Proposed_YARN_Service_Registry.pdf, 
> 2014-09-08_YARN_Service_Registry.pdf, RegistrationServiceDetails.txt, 
> YARN-913-001.patch, YARN-913-002.patch, YARN-913-003.patch, 
> YARN-913-003.patch, YARN-913-004.patch, YARN-913-006.patch, 
> YARN-913-007.patch, YARN-913-008.patch, yarnregistry.pdf, yarnregistry.tla
>
>
> In a YARN cluster you can't predict where services will come up -or on what 
> ports. The services need to work those things out as they come up and then 
> publish them somewhere.
> Applications need to be able to find the service instance they are to bond to 
> -and not any others in the cluster.
> Some kind of service registry -in the RM, in ZK, could do this. If the RM 
> held the write access to the ZK nodes, it would be more secure than having 
> apps register with ZK themselves.



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