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From "Sandy Ryza (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (YARN-417) Add a poller that allows the AM to receive notifications when it is assigned containers
Date Tue, 19 Mar 2013 18:31:15 GMT

    [ https://issues.apache.org/jira/browse/YARN-417?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13606643#comment-13606643
] 

Sandy Ryza commented on YARN-417:
---------------------------------

bq. The client can make a call to stop() before making a call to unregister (bad code, race
in code, client got reboot from RM etc) In that case the code may crash according to the sequence
I described earlier, wont it? so the safety of unregister having being called before stop
is not guaranteed, right? Calling client.stop() after heartbeat.join() is the right thing
to do irrespective of any safety offered by some other method call (that may or may not happen).
Let us do that unless there is a good reason not to.

I agree.

bq. There was a burden on the app to call heartbeat periodically. We are removing that burden
in this jira. A related burden was to update progress periodically which was tied to the heartbeat.
From what I see, remembering to update the progress periodically is still a burden on the
app. Is it not so?

The app does not need to update progress periodically, it only needs to update it in response
to events that would change its progress, which it needs to do anyway.  This of course can
be accomplished just as easily by updating a user-stored progress variable and returning it
to a getProgress callback.  The reason that I am defending the former is that currently we
have a clear separation that callbacks are for information relayed from the RM, and AMRMClientAsync
direct method calls like newContainerRequest, setProgress, and registerApplicationMaster are
for information to the RM.  Having gotten that out, I'll accept whatever approach seems best
to you, Bikas.
                
> Add a poller that allows the AM to receive notifications when it is assigned containers
> ---------------------------------------------------------------------------------------
>
>                 Key: YARN-417
>                 URL: https://issues.apache.org/jira/browse/YARN-417
>             Project: Hadoop YARN
>          Issue Type: Sub-task
>          Components: api, applications
>    Affects Versions: 2.0.3-alpha
>            Reporter: Sandy Ryza
>            Assignee: Sandy Ryza
>         Attachments: AMRMClientAsync-1.java, AMRMClientAsync.java, YARN-417-1.patch,
YARN-417-2.patch, YARN-417-3.patch, YARN-417-4.patch, YARN-417-4.patch, YARN-417.patch, YarnAppMaster.java,
YarnAppMasterListener.java
>
>
> Writing AMs would be easier for some if they did not have to handle heartbeating to the
RM on their own.

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