It could include the following work items
1. Define the OS independent SignalContainerCMD enum commands. We will start with known requirements such as KILL. We can expand the list later.
2. Add a new method signalContainer to ApplicationClientProtocol. signalContainerRequest will include containerId as well as SignalContainerCMD.
3. Add signalContainer method to YarnClient and YarnClientImpl.
4. RM will deliver the request to the RMNode object that owns the container.
5. RM needs to have the proper authorization for the signal request.