Allow IO::Endpoint::Wrapper#accept to accept task:

[korbin]

I'm currently in the process of migrating from Puma to Falcon and was looking for a way to throttle the incoming request queue so that my upstream nginx reverse proxy doesn't overload a single thread with Fibers-per-request - someone else had this issue as well.

I'd like to prevent the actual Socket accept from happening until capacity is available:

This may or may not be the best way to go about this and this behavior should probably be customizable, but, I would abstractly like to be able to:

def accept(server, timeout: nil, linger: nil, task: Task.current, **options, &block)
  loop do
    task.async do
      socket, address = server.accept

      if linger
        socket.setsockopt(SOL_SOCKET, SO_LINGER, 1)
      end

      if timeout
        set_timeout(socket, timeout)
      end

      # Some sockets, notably SSL sockets, need application level negotiation before they are ready:
      if socket.respond_to?(:start)
        begin
          socket.start
        rescue
          socket.close
          raise
        end
      end

      # It seems like OpenSSL doesn't return the address of the peer when using `accept`, so we need to get it from the socket:
      address ||= socket.remote_address

      yield socket, address
    end
  end
end

And then in Falcon, I can pass an Async::Semaphore to the endpoint.

This is currently working with the above monkey-patched into the class (in config/falcon.rb) - maybe there's a cleaner abstraction.