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https://issues.apache.org/jira/browse/TEZ-3892?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16388367#comment-16388367
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Prasanth Jayachandran commented on TEZ-3892:
--------------------------------------------

changes look good to me.. would be good to have someone for tez take another 
stab.. 

> getClient API for TezClient
> ---------------------------
>
>                 Key: TEZ-3892
>                 URL: https://issues.apache.org/jira/browse/TEZ-3892
>             Project: Apache Tez
>          Issue Type: New Feature
>            Reporter: Eric Wohlstadter
>            Assignee: Eric Wohlstadter
>            Priority: Major
>         Attachments: TEZ-3892.1.patch, TEZ-3892.2.patch
>
>
> This is a proposed opt-in feature.
> Tez AM already supports long-lived sessions, if desired a AM session can live 
> indefinitely.
> However, new clients cannot connect to a long-lived AM session through the 
> standard TezClient API. 
> TezClient API only provides a "start" method to initiate a connection, which 
> always allocates a new AM from YARN.
>  # For interactive BI use-cases, this startup time can be significant.
>  # Hive is implementing a HiveServer2 High Availability feature.
>  ** When the singleton HS2 master server fails, the HS2 client is quickly 
> redirected to a pre-warmed HS2 backup. 
>  # For the failover to complete quickly end-to-end, a Tez AM must also be 
> pre-warmed and ready to accept connections.
> For more information, see design for: 
> https://issues.apache.org/jira/browse/HIVE-18281.
> ----
> Anticipated changes:
>  # A getClient{{(ApplicationId)}} method is added to TezClient. The 
> functionality is similar to {{start}}
>  ** Code related to launching a new AM from the RM is factored out.
>  ** Since {{start}} and getClient will share some code, this code is 
> refactored into reusable helper methods.
>  ** A usage example is added to {{org/apache/tez/examples}}
>  # It is not a goal of this JIRA to ensure that running Tez DAGs can be 
> recovered by a client using the getClient API. The goal is only for 
> maintaining a pool of warm Tez AMs to skip RM/container/JVM startup.



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