@Override
  public Object deallocateContainer(ContainerId containerId) {
    LOG.debug("Ignoring deallocateContainer for containerId: {}", containerId);
    // Containers are not being tracked for re-use.
    // This is safe to ignore since a deallocate task will come in.
    return null;
  }
The difference between this and getTotalResources() is that this only gives currently free
resource instances, while the other lists all the instances that may become available in a
while.
llap-tez/src/java/org/apache/hadoop/hive/llap/tezplugins/LlapTaskSchedulerService.java