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From "Varun Saxena (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (YARN-6357) Implement TimelineCollector#putEntitiesAsync
Date Wed, 22 Mar 2017 17:44:41 GMT

    [ https://issues.apache.org/jira/browse/YARN-6357?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15936770#comment-15936770
] 

Varun Saxena commented on YARN-6357:
------------------------------------

The way current code is structured, the responsibility of the writer is merely to buffer data
and write it out.
The control of when to flush is still with the collector i.e. the timer to flush. So the reasoning
from my side is that the control of flush from sync API can also be with the collector.
However, this is not something which I feel strongly about so let us do whatever most of the
people think.

> Implement TimelineCollector#putEntitiesAsync
> --------------------------------------------
>
>                 Key: YARN-6357
>                 URL: https://issues.apache.org/jira/browse/YARN-6357
>             Project: Hadoop YARN
>          Issue Type: Sub-task
>          Components: ATSv2, timelineserver
>    Affects Versions: YARN-2928
>            Reporter: Joep Rottinghuis
>            Assignee: Haibo Chen
>              Labels: yarn-5355-merge-blocker
>         Attachments: YARN-6357.01.patch, YARN-6357.02.patch
>
>
> As discovered and discussed in YARN-5269 the TimelineCollector#putEntitiesAsync method
is currently not implemented and TimelineCollector#putEntities is asynchronous.
> TimelineV2ClientImpl#putEntities vs TimelineV2ClientImpl#putEntitiesAsync correctly call
TimelineEntityDispatcher#dispatchEntities(boolean sync,... with the correct argument. This
argument does seem to make it into the params, and on the server side TimelineCollectorWebService#putEntities
correctly pulls the async parameter from the rest call. See line 156:
> {code}
>     boolean isAsync = async != null && async.trim().equalsIgnoreCase("true");
> {code}
> However, this is where the problem starts. It simply calls TimelineCollector#putEntities
and ignores the value of isAsync. It should instead have called TimelineCollector#putEntitiesAsync,
which is currently not implemented.
> putEntities should call putEntitiesAsync and then after that call writer.flush()
> The fact that we flush on close and we flush periodically should be more of a concern
of avoiding data loss; close in case sync is never called and the periodic flush to guard
against having data from slow writers get buffered for a long time and expose us to risk of
loss in case the collector crashes with data in its buffers. Size-based flush is a different
concern to avoid blowing up memory footprint.
> The spooling behavior is also somewhat separate.
> We have two separate methods on our API putEntities and putEntitiesAsync and they should
have different behavior beyond waiting for the request to be sent.



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