Grequests incompatible with Flask-SocketIO

[ocervell]

Hi,

I am not able to make asynchronous requests with grequests from inside a socket.

My code is the following:

@socketio.on('api_query', namespace='/display')
def get_api(data):
    urls = get_urls(data)
    namespace = '/display'
    flask_context = {
        'app': app,
        'request': request,
        'sid': request.sid,
        'namespace': namespace
    }
    def hook_req(response, *args, **kwargs):
        if response.status_code != 200:
            logger_ui.error('%s | Receive API response failure' % response.status_code)
            return
        data = {
          'api_call': SOLID*2 + "<br>- " + response.url + "<br>" + SOLID*2,
          'response': response.json()
        }
        emit_with_context(flask_context, 'api_response', data)
    (grequests.get(u, hooks={'response': hook_req}, auth=(session['token'], '')) for u in urls)
    emit('end_stream')

def emit_with_context(flask_context, event, data={}):
    """ Send through SocketIO a message named 'event' with 'data' as a content.
    """
    if flask_context is None:
        return
    from flask.ext.socketio import emit
    app = flask_context['app']
    namespace = flask_context['namespace']
    sid = flask_context['sid']
    with app.test_request_context():
        request = flask_context['request']
        request.sid = sid
        if data:
            emit(event, data, namespace=namespace)
        else:
            emit(event, namespace=namespace)

This code works perfectly using requests module but I need asynchronous calls to speed up things. When I switch to grequests my API backend doesn't receive the requests anymore. My backend is able to receive asynchronous requests.

I'm running Flask-SocketIO with gevent.

Initially I thought this was related to #55 but it's been fixed and I'm running the Flask server without debug mode.

Any idea ?

[ocervell]

I replaced grequests by unirest and it now works perfectly. I had to add the following on top of my file so that the emit_with_context calls would not block:

import eventlet
eventlet.monkey_patch()

New code is the same except that the following:
(grequests.get(u, hooks={'response': hook_req}, auth=(session['token'], '')) for u in urls)

has been replaced by:

for u in urls:
        unirest.get(u, callback=hook_req, auth=(session['token'], ''))

[miguelgrinberg]

@ocervell the problem is in the emit_with_context. You are using a test request context in there, that does not have enough information to make the emit() function work correctly.

Instead of emit() which is context-dependent, try using socketio.emit() and including the sid of the user or room you want to emit to. That should work even w/o a Flask context.