Improve Supervision

[pbayer]

This is a collection of various improvements to supervision (implemented in issue #16):

• [x] remote actor restart on the same PIDs,
• [x] supervision of registered actors (see comment below),
• [x] identify supervised actors by name (see comment below),
• [x] make the supervisor API thoroughly work with registered actor names,
• [ ] functionality to kill a running actor,
• [ ] ensure an actor is shutdown in a given timeframe,
• [ ] ensure a supervisor is restarted (with childs) in a given timeframe,

Task supervision

I have to look further into the following:

• [ ] How to tackle (long) running tasks at supervisor shutdown,
• [ ] How about tasks running on remote processes?

[pbayer]

Supervision of registered actors

If remote actors communicate with each other over RemoteChannels, several copies of an actor link may exist on different workers. After restart of an actor those links get out of sync!

I that case those actors must be registered and the supervisor supervises a registered actor name and updates the link for that name after actor restart. The registry then is the one place having a current link to the remote actor.

Note

It is better not to enforce remote actor registration since in a strictly hierarchical network topology with the supervisor running at the root node this is not strictly needed.

[pbayer]

Identify supervised actors by name

Currently after actor restart due to a node failure the supervisor gives a warning restarting @unknown on pid x. This makes no sense for diagnosis.

Therefore actors must be identifiable and be identified either by their Proquint string or by their registered name. Three changes are necessary to the:

• [ ] info function,
• [ ] Child struct,
• [ ] error-handling warnings