Back-to-back event receiving with gevent

[rayalan]

I'm seeing a problem with receiving multiple events in v0.5.2. I have a browser that sends multiple events. However, flask-uwsgi-websocket only reads 1 event every timeout seconds (30, in my case). I believe the problem is two-fold:

1. _gevent.py, line 70: The max receive queue size shouldn't be limited to 1.
2. The clause around recv_is_set() should make sure that it reads all the events, with a minimum of one event. This seems to work for me:

elif recv_event.is_set():
    try:
        incoming_event = None
        is_first = True
        while incoming_event or is_first:
            incoming_event = uwsgi.websocket_recv_nb()
            if is_first or incoming_event:
                recv_queue.put(incoming_event)
            is_first = False
        recv_event.clear()
        listening = spawn(listener, client)
    except IOError:
        client.connected = False

The above can be cleaned up quite a bit. I also suspect that it is safe to reset the clear() flag before we finish reading all the current events. However, I rearranged it for testing purposes and I haven't gone back and verified that theory.

[rayalan]

I dug into this a bit more. There seem to be a couple issues doing on here:

1. Suppose that client.fd receives 200 bytes. As long as no bytes have been read, select(client.fd, [], timeout) returns instantly. As soon as a byte has been read, select(client.fd, [], timeout) takes timeout to return -- regardless of whether 1 or 200 bytes have been read.
2. Some browsers seem to send back-to-back empty messages, which all need to get read from the system. If empty messages are left unread, they seem to prevent PONG messages from being sent (I'm not sure in which direction), which causes the socket to timeout. I ended up with this implementation:

            elif recv_event.is_set():
                recv_event.clear()
                try:
                    message = True
                    while message:
                        message = uwsgi.websocket_recv_nb()
                        recv_queue.put(message)
                    listening = spawn(listener, client)
                except IOError:
                    client.connected = False

It ends up writing an empty message for every event, but better than the alternatives.

[zeekay]

That seems like a nice solution, would you like to send a PR?

[rayalan]

I will; it may be a couple days.

[rayalan]

Created #48