HADOOP-8468 propose network topology changes for running on virtualized infrastructure, which includes:
1. Add "NodeGroup" layer in new NetworkTopology (also known as NetworkTopologyWithNodeGroup):
2. Update Replica Placement/Removal Policy to reflect new topology layer:
3. Update balancer policy:
4. Update Task Scheduling Policy to reflect new topology layer and support the case that compute nodes (NodeManager or TaskTracker) and data nodes are separated into different VMs, but still benefit from physical host locality: YARN-18, YARN-19.
This JIRA will address the backport work on branch-1 which will be divided into 4 issues/patches in related jira issues.