Manila Data Copy Service

A standalone Manila service which purpose is to receive requests, process data operations such as copying, share migration, backup, and send back the response after operation has been completed.

Currently, data copy operations that take a long time have no dedicated service to run on, so if for instance share migration operation is requested, the manila-share service blocks copying data, which can possibly take a very long time to complete, thus preventing all further requests that require interacting with that backend from being processed. The same would happen for manila-api or manila-scheduler services if they were to perform data copy operations.

The main use case right now is Share Migration:
- Share Migration of Share X from backend A to backend B is requested.
- Backend A's vendor is different than backend B's vendor, so fallback migration approach is used.
- Backend A creates instance in backend B through RPC call.
- Backend A calls Data Copy Service to start copying.
- Data Copy Service migration copy method implementation allows access to its IP, according to configuration.
- Data Copy Service mounts Backend A's share X instance and Backend B's share X instance, and copies data from one to the other.
- Data Copy Service notifies Backend A through RPC that the request has been completed (Optional phase 2)
- Backend A deletes its share X instance and calls Backend B to apply access rules to its share X instance.
- Share Migration of share X completes.

Another use case that would use Data Copy Service is Share Backup, but this feature has not yet been designed for Manila.