Moksha+Pyramid - 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 pyramid
$ pip install moksha.wsgi moksha.hub
$ # Also, install weberror for kicks.
$ pip install weberror

Use pcreate to setup a Pyramid scaffold, install dependencies, and verify that its working. I like the alchemy scaffold, so we’ll use that one.

$ pcreate -t alchemy tutorial
$ cd tutorial/
$ rm production.ini  # moksha-hub gets confused when this is present.
$ python setup.py develop
$ initialize_tutorial_db development.ini
$ pserve --reload development.ini

Visit http://localhost:6543 to check it out. Success.

Enable ToscaWidgets2 and Moksha Middlewares

Go and edit development.ini. There should be a section at the top named [app:main]. Change that to [app:tutorial]. Then, just above the [server:main] section add the following three blocks:

[pipeline:main]
pipeline =
    egg:WebError#evalerror
    tw2
    moksha
    tutorial

[filter:tw2]
use = egg:tw2.core#middleware

[filter:moksha]
use = egg:moksha.wsgi#middleware

You now have three new pieces of WSGI middleware floating under your pyramid app. Neat! Restart pserve and check http://localhost:6543 to make sure its not crashing.

See also

• Moksha Middleware

Provide some configuration for Moksha

Edit development.ini and add the following lines in the [app:tutorial] section. Do it just under the sqlalchemy.url line:

##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

Your first Polling Producer

Add a new file in tutorial/producers.py. In it, 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!")

As well, edit setup.py and modify the entry_points section to include a declaration of this new producer like so:

[moksha.producer]
hello = tutorial.producers: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

Create a new file in tutorial/widgets.py. In it, add the following definition:

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 = ""

You’ll need to expose this widget and the moksha global resources to your templates. You could do this with Pyramid’s events infrastructure and inject them into every page that gets served, but we’ll just dumbly expose them in the default /home view for this scaffold.

Edit tutorial/views.py and add the following imports at the top:

import tutorial.widgets
from moksha.wsgi.widgets.api import get_moksha_socket

In the same file, change the return statement of my_view() to return the following:

return {
    'one':one,
    'project':'tutorial',
    'notification_widget': tutorial.widgets.PopupNotification,
    'moksha_socket': get_moksha_socket(request.registry.settings),
}

Finally, display the widget on your page by editing tutorial/templates/mytemplate.pt and adding the following at the end but just inside of the </body> tag:

<div tal:content="structure notification_widget.display()"></div>
<div tal:content="structure moksha_socket.display()"></div>

Go restart your pserve server and check out http://localhost:6543 again. You should see popups from your PollingProducer.

See also

• Live Widgets