As per discussion in
YARN-7613. Lets expose canAssign method in the PlacementConstraintManager that takes a sourceTags, applicationId, SchedulerNode and AllocationTagsManager and returns true if constraints are not violated by placing the container on the node.
I prefer not passing in the SchedulingRequest, since it can have > 1 numAllocations. We want this api to be called for single allocations.