RBF: Datanodes interacting with Routers

Datanodes talk to particular Namenodes. We could use the Router infrastructure for the Datanodes to register/heartbeating into them and the Routers would forward this to particular Namenodes. This would make the assignment of Datanodes to subclusters potentially more dynamic.

The implementation would potentially include:

• Router to implement part of DatanodeProtocol
• Forwarding DN messages into Routers
• Policies to assign datanodes to subclusters
• Datanodes to make blockpool configuration dynamic