Yagi

A PubSubHubBub Publisher implementation in Python

Why PubSubHubBub?

We wanted to use a defined spec with easy to use clients, and PubSubHubBub fit the bill nicely.

Why implement an external publisher?

The original impetus for this project is to adapt an existing piece of software to sending notifications without laying the job of managing those notifications on said implementation. Because PubSubHubBub requires an ATOM feed, we didn't want the original software from having to worry about completely unrelated functionality. Additionally, this route buys us a lot of flexibility.

Dependencies:

• argparse
• feedgenerator
• httplib2
• redis
• webob
• eventlet
• daemon
• pubsubhubbub_publish (available under the publisher_clients folder after checking out the project from Google Code NOTE: the plan is to replace this dependency later with our implementation
• carrot (if using Rabbit)
• routes

Setting up the hub

Download the Google App Engine SDK for Linux and add it to your path

http://code.google.com/appengine/downloads.html

Then checkout the reference hub.

svn checkout http://pubsubhubbub.googlecode.com/svn/trunk/ pubsubhubbub-read-only

Install pubsubhubbub_publisher for python

cd pubsubhubbub-read-only/publisher_clients/python
sudo python setup.py install

Start the hub

cd pubsubhubbub-read-only
dev_appserver.py hub/ -p<port number specified in yagi.conf>

Setting up Yagi

After setting up the hub, above

cd yagi
# edit yagi.conf, setting up as appropriate
# Take care to update the feed_host variable in the event_feed
# section as it will be the IP address presented in the feed. Otherwise
# Yagi will attempt to infer it, and it doesn't seem to be all that
# successful at it.
sudo cp yagi.conf /etc
sudo python setup.py install
yagi-event
yagi-feed

Testing subscriptions

cd yagi

# You'll want to run this in multiple screen windows or terminal sessions, as the callback process
# won't daemonize

python subscriber/callback.py <sub_port>
python subscriber/sub.py <topic> <callback> <hub>

# I usually load other/push_rabbit.py in an iPython session
cd other
ipython
import push_rabbit

# the cast below is assuming you setting up yagi to listen on a queue named 'notifications.warn'
push_rabbit.cast(dict(a=3), 'instance', 'notifications', 'warn')

You should see XML content being pushed to your window running callback.py, above.