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Sunil G commented on YARN-2022:
-------------------------------
Thank you very much Carlo for the review.
As per your concern about AM Container priority, I am using a static final
variable named AM_CONTAINER_PRIORITY from RMAppAttemptImpl to check whether a
container is AM or not.
As per my code review, this variable is not been set by user [RM only uses this
to create an AM container Resource Request]. Hence there is no much problem in
using the same.
Secondly for the corner cases, I agree with your point. In a specific corner
case it is possible that 100% AM can take over a queue.
1. maximum-am-resource-percent is in cluster level and we can get maximum
runnable applications. Actual total running applications count can also be
fetched from all leaf queues.
With these two, a checkpoint can be derived as you have mentioned.
2. user-limit-factor will set a user limit quota among total resources for each
user. If preemption has to be done among applications, currently only
application timestamp is considered [reverse order].
So how this factor can help in giving a checkpoint for saving AM. Could you
please share your thoughts on this point.
I will work on defining checkpoint for saving AM and will update. Meanwhile
please check whether my explanation is in-line with you thoughts. Thank you.
> Preempting an Application Master container can be kept as least priority when
> multiple applications are marked for preemption by
> ProportionalCapacityPreemptionPolicy
> ---------------------------------------------------------------------------------------------------------------------------------------------------------------------
>
> Key: YARN-2022
> URL: https://issues.apache.org/jira/browse/YARN-2022
> Project: Hadoop YARN
> Issue Type: Improvement
> Components: resourcemanager
> Affects Versions: 2.4.0
> Reporter: Sunil G
> Assignee: Sunil G
> Attachments: Yarn-2022.1.patch
>
>
> Cluster Size = 16GB [2NM's]
> Queue A Capacity = 50%
> Queue B Capacity = 50%
> Consider there are 3 applications running in Queue A which has taken the full
> cluster capacity.
> J1 = 2GB AM + 1GB * 4 Maps
> J2 = 2GB AM + 1GB * 4 Maps
> J3 = 2GB AM + 1GB * 2 Maps
> Another Job J4 is submitted in Queue B [J4 needs a 2GB AM + 1GB * 2 Maps ].
> Currently in this scenario, Jobs J3 will get killed including its AM.
> It is better if AM can be given least priority among multiple applications.
> In this same scenario, map tasks from J3 and J2 can be preempted.
> Later when cluster is free, maps can be allocated to these Jobs.
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