refactor connection to use MessagePack instead of JSON

[ggmichaelgo]

Types of Changes

• Bug fix.
• New feature.
• Performance improvement.

PR Summary

Instead of using JSON string for communicating between supervisor and workers, use MessagePack instead for better performance and String safety.

Async::Container::Supervisor::MessageWrapper has been newly introduced to this gem.
The MessageWrapper normalizes the message object by invoking the message object's as_json function.

Connection uses the new MessageWrapper and for now I have configured it to have 4GiB. (maximum value from unsigned 32-bit int / may be unsigned 16-bit int with 65KB will be enough 🤔)

Contribution

• I added tests for my changes.
• I tested my changes locally.
• I agree to the Developer's Certificate of Origin 1.1.

[samuel-williams-shopify]

We don't need to add our own framing:

require "msgpack"
require "socket"
require "async"

factory = MessagePack::Factory.new
sockets = Socket.pair(:UNIX, :STREAM)

packer = factory.packer(sockets[0])
unpacker = factory.unpacker(sockets[1])

Async do
	Async do
		while true
			puts unpacker.read
		end
	end

	Async do
		while true
			packer.write("Hello, World #{Time.now}!")
			packer.flush
			sleep rand
		end
	end
end

MessagePack already knows how long each message is internally. (flush is not strictly needed, it's just to ensure the message is sent across the wire at that time - it does not impact framing).