Moksha+Flask - Hello World Tutorial¶

Note

You can find the source for this tutorial on github.

Bootstrapping¶

Set up a virtualenv and install Moksha and Pyramid (install virtualenvwrapper if you haven’t already).

$ mkvirtualenv tutorial
$ pip install Flask
$ pip install moksha.wsgi moksha.hub
$ mkdir tutorial
$ cd tutorial

Copy this dummy flask app into a file called tutorial.py. It may look familiar to you.

from flask import Flask
app = Flask(__name__)

@app.route("/")
def hello():
    return "Hello World!"

if __name__ == "__main__":
    app.run()

Give it a run to see if it works:

python tutorial.py

Visit http://localhost:5000 to check it out. Success.

Add a configuration file¶

Create a development.ini file with the following contents:

[app:main]
#moksha.domain = live.example.com
moksha.domain = localhost

moksha.notifications = True
moksha.socket.notify = True

moksha.livesocket = True
moksha.livesocket.backend = websocket
#moksha.livesocket.reconnect_interval = 5000
moksha.livesocket.websocket.port = 9998

zmq_enabled = True
#zmq_strict = True
zmq_publish_endpoints = tcp://*:3000
zmq_subscribe_endpoints = tcp://127.0.0.1:3000

Enable ToscaWidgets2 and Moksha Middlewares¶

Wrap your app in WSGI middleware by first adding the following imports to the top of your file:

from moksha.common.lib.helpers import get_moksha_appconfig
from moksha.wsgi.middleware import make_moksha_middleware
from tw2.core.middleware import make_middleware

And also edit the if __name__ == "__main__": section to look like this:

if __name__ == "__main__":
    # Load development.ini
    config = get_moksha_appconfig()

    # Wrap the inner wsgi app with our middlewares
    app.wsgi_app = make_moksha_middleware(app.wsgi_app, config)
    app.wsgi_app = make_middleware(app.wsgi_app)

    app.run()

You now have two new pieces of WSGI middleware floating under your Flask app. Neat! Restart the app and check http://localhost:5000 to make sure its not crashing.

Your first Polling Producer¶

Go back and edit tutorial.py and add the following definition:

import datetime
import moksha.hub.api.producer

class HelloWorldProducer(moksha.hub.api.producer.PollingProducer):
    frequency = datetime.timedelta(seconds=2)

    def poll(self):
        self.send_message('hello_world', "Hello World!")

Moksha’s ability to find producers and consumers is dependent on setuptools, so you’ll need to add a setup.py file with the following contents:

from setuptools import setup
setup(
    name='tutorial',
    entry_points="""
    [moksha.producer]
    hello = tutorial:HelloWorldProducer
    """,
)

Open up a second terminal, activate your virtualenv with workon tutorial and run the moksha-hub:

$ workon tutorial
$ python setup.py develop
$ moksha-hub

This will start up the hub which should pick up and load your HelloWorldProducer. Keep this running in your second terminal as you go on to create the frontend components.

Your first LiveWidget¶

Edit tutorial.py again and add the three following imports at the top:

import moksha.wsgi.widgets.api
import tw2.jqplugins.gritter
import flask.templating

Add the following widget definiton:

import moksha.wsgi.widgets.api
import tw2.jqplugins.gritter

class PopupNotification(moksha.wsgi.widgets.api.LiveWidget):
    topic = "*"
    onmessage = "$.gritter.add({'title': 'Received', 'text': json});"
    resources = moksha.wsgi.widgets.api.LiveWidget.resources + \
            tw2.jqplugins.gritter.gritter_resources
    backend = "websocket"

    # Don't actually produce anything when you call .display() on this widget.
    inline_engine_name = "mako"
    template = ""

Finally, you need to expose this widget through a Flask route. Blow away the existing def hello() route and replace it with the following:

simple_template = """
<html>
<head></head>
<body>
Really?
{{notification_widget.display()}}
{{moksha_socket.display()}}
</body>
</html>
"""


@app.route("/")
def hello():
    config = get_moksha_appconfig()
    socket = moksha.wsgi.widgets.api.get_moksha_socket(config)
    return flask.templating.render_template_string(
        simple_template,
        notification_widget=PopupNotification,
        moksha_socket=socket,
    )

Go restart your app (make sure moksha-hub is running in a second terminal) and check out http://localhost:5000 again. You should see popups from your PollingProducer.