General async runtime

Fig: General async runtime based execution model for laminarmq

This execution model is based on the executor, reactor, waker abstractions used by all rust async runtimes. We don't have to specifically care about how and where a particular future is executed.

The data flow in this execution model is as follows:

• A HTTP server future parses HTTP requests from the request socket
• For every HTTP request it creates a new future to handle it
• The HTTP handler future sends the request and a response channel tx to the request router via a channel. It also awaits on the response rx end.
• The request router future maintains a map of partition_id to designated request channel tx for each partition controller future.
• For every partition request received it forwards the request on the appropriate partition request channel tx. If a partition::create(...) request is received it creates a new partition controller future.
• The partition controller future send back the response to the provided response channel tx.
• The response poller future received it and responds back with a serialized response to the socket.

All futures are spawned using the async runtime's designated {…}::spawn(…) method. We don't have to specify any details as to how and where the future's corresponding task will be executed.