Kuhu Shukla created YARN-4280:
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Summary: CapacityScheduler reservations may not prevent indefinite
postponement on a busy cluster
Key: YARN-4280
URL: https://issues.apache.org/jira/browse/YARN-4280
Project: Hadoop YARN
Issue Type: Bug
Components: capacity scheduler
Affects Versions: 2.7.1, 2.6.1, 2.8.0
Reporter: Kuhu Shukla
Assignee: Kuhu Shukla
Consider the following scenario:
There are 2 queues A(25% of the total capacity) and B(75%), both can run at
total cluster capacity. There are 2 applications, appX that runs on Queue A,
always asking for 1G containers(non-AM) and appY runs on Queue B asking for 2
GB containers.
The user limit is high enough for the application to reach 100% of the cluster
resource.
appX is running at total cluster capacity, full with 1G containers releasing
only one container at a time. appY comes in with a request of 2GB container but
only 1 GB is free. Ideally, since appY is in the underserved queue, it has
higher priority and should reserve for its 2 GB request. Since this request
puts the alloc+reserve above total capacity of the cluster, reservation is not
made. appX comes in with a 1GB request and since 1GB is still available, the
request is allocated.
This can continue indefinitely causing priority inversion.
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