[jira] [Created] (YARN-8149) Revisit behavior of Re-Reservation in Capacity Scheduler

["Wangda Tan (JIRA)" <ji...@apache.org>]

Wangda Tan created YARN-8149:
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             Summary: Revisit behavior of Re-Reservation in Capacity Scheduler
                 Key: YARN-8149
                 URL: https://issues.apache.org/jira/browse/YARN-8149
             Project: Hadoop YARN
          Issue Type: Bug
            Reporter: Wangda Tan


Frankly speaking, I'm not sure why we need the re-reservation. The formula is not that easy to understand:

Inside: {{org.apache.hadoop.yarn.server.resourcemanager.scheduler.capacity.allocator.RegularContainerAllocator#shouldAllocOrReserveNewContainer}}
{code:java}
starvation = re-reservation / (#reserved-container * 
     (1 - min(requested-resource / max-alloc, 
              max-alloc - min-alloc / max-alloc))
should_allocate = starvation + requiredContainers - reservedContainers > 0{code}
I think we should be able to remove the starvation computation, just to check requiredContainers > reservedContainers should be enough.

In a large cluster, we can easily overflow re-reservation to MAX_INT, see YARN-7636. 

 



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