gevent with uwsgi requires ping/pong

[MattWycklendt]

I am having an issue where the client does not receive emits from the server unless it sends a message. To recreate the issue run the example app in the Flask-SocketIO library and comment out the ping/pong functions in the client library (currently lines 38 to 57). Run the server with uwsgi and gevent using the command listed in the docs. If I send an ECHO message to the server the client doesn't get any response back until sending another ECHO message.

[MattWycklendt]

Note that the ping I am talking about is not the engineIO ping timeout. This issue occurs immediately after the web socket connection.

[miguelgrinberg]

When you say

If I send an ECHO message to the server the client

Do you mean typing ECHO in the first text box from the example in this repository, or is it something else? If you are using your own code, messages that are sent do not receive a response, unless you request a callback.

[MattWycklendt]

@miguelgrinberg Sorry, I probably wasn't clear in my description. I am not using my own code, only the example code provided in the repo with a couple lines commented out. Below are more detailed steps:

1. I cloned the Flask-SocketIO library.
2. I installed gevent and uwsgi in my virtual environment.
3. In /examples/templates/index.html I commented out the interval timer to emit a my_ping message, and listen to my_pong message. This is equivalent to commenting out lines 38 to f7.
4. Run the app with uwsgi in the example directory using the command uwsgi --http :5000 --gevent 1000 --http-websockets --master --wsgi-file app.py --callable app
5. In the browser start sending messages in the first echo text box. If I type msg1 I expected to see that echoed back but nothing happened. If I enter msg2 in the text box I see msg1 come back. If I then enter msg3 in the text box I see msg2 come back... Basically I was only recieving echo messages from the server after entering another echo message.

[miguelgrinberg]

Sorry for the misunderstanding. I have now reproduced the issue.

It appears I inadvertently introduced this bug in miguelgrinberg/python-engineio@d158423, by changing the method to read the websocket file handle.

Please upgrade python-engineio to version 1.2.4. I think with that upgrade uwsgi will behave.

[MattWycklendt]

Working. Thanks!