Found an issue:
When DefaultContainerCalculator is enabled and opportunistic container allocation is disabled. It is possible that for a NM:
When this happens, ContainerScheduler will report errors like:
ContainerScheduler (ContainerScheduler.java:pickOpportunisticContainersToKill(458)) - There are no sufficient resources to start guaranteed.
This will be an incompatible change after 2.8 because before
YARN-6706, we can start containers when DefaultContainerCalculator is configured and vcores is overallocated.