Mit Desai commented on YARN-4183:

Here is the scenario. We want the Yarn application to not use the timeline 
server during execution but use the application history server for the logs. 
This will not be possible with the current implementation. It is either both or 

If we check for application history enabled, it indirectly tells that timeline 
service is enable. Because history server will not be enabled without enabling 
the timeline server. This way, the system metrics publisher can publish events 
to the history server even if the applications do not use the timeline server 
for execution.

> Enabling generic application history forces every job to get a timeline 
> service delegation token
> ------------------------------------------------------------------------------------------------
>                 Key: YARN-4183
>                 URL: https://issues.apache.org/jira/browse/YARN-4183
>             Project: Hadoop YARN
>          Issue Type: Bug
>    Affects Versions: 2.7.1
>            Reporter: Mit Desai
>            Assignee: Mit Desai
>         Attachments: YARN-4183.1.patch
> When enabling just the Generic History Server and not the timeline server, 
> the system metrics publisher will not publish the events to the timeline 
> store as it checks if the timeline server and system metrics publisher are 
> enabled before creating a timeline client.
> To make it work, if the timeline service flag is turned on, it will force 
> every yarn application to get a delegation token.
> Instead of checking if timeline service is enabled, we should be checking if 
> application history server is enabled.

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