django-trello-webhooks 0.2

Django Trello Webhooks - Trello callback integration for Django.

Django application for managing Trello webhooks.

*LOOKING FOR CONTRIBUTORS*

Status

It lives!

The app currently works (on my machine) - so is really now at the “proof of concept” stage. I haven’t packaged it properly, there are no tests (none at all), but it does really work.

Background

Trello webhooks can only be managed programmatically via the API, which is clever, but also a massive PITA. In addition, whilst creating a new webhook, Trello will immediately call the registered callback URL with a HEAD request to verify that it exists. This makes setting up webhooks fiddly and complex (esp. when experimenting in a local development environment).

This project is a Django app that makes managing Trello webhook easy. Well, easier. It exposes Trello webhooks through the Django admin site as standard Django models that can be created and deleted through a web UI. Incoming webhook events are then exposed via Django signals that are raised, and can be integrated into your application.

How does it work?

Each webhook is modelled as a Django model (Webhook), and each callback received on the webhook is modelled as a CallbackEvent object that contains the JSON payload (so it will maintain a complete history of all callbacks).

The Webhook.save() method is used to register the webhook with the Trello API. The corresponding delete method is used to delete the webhook from Trello.

The app contains a single view function, api_callback, which receives the callback from Trello, and which also supports the synchronous activation of new webhooks by Trello. (When you create a webhook via the Trello API, they will immediately issue a HEAD request to the callback url supplied, so you need to be able to handle this immediately.)

The important bit is then how you use the callback in your application. This is done via Django signals. On each webhook callback, the app sends the callback_received signal, passing in the data received via the callback.

Your application then connects via this signal:

from django.dispatch import receiver

from trello_webhooks.signals import callback_received

@receiver(callback_received, dispatch_uid="callback_received")
def on_callback_received(sender, **kwargs):
    event = kwargs.pop('event')
    print "This is the event payload: ", event.event_payload

There is a Django management command which can be used to synchronise any existing webhooks (in both directions), called sync_webhooks. Run on its own, without any arguments, this will look up all the webhooks in the local Django database, and sync then with Trello (creating them if they don’t already exist). It will also check Trello for any webhooks that it has registered that do not exist locally, and create them.

Configuration

There are three mandatory environment settings (following the 12-factor app principal):

• TRELLO_API_KEY

• TRELLO_API_SECRET

• CALLBACK_DOMAIN

The first two are the core Trello developer API keys - available from here: https://trello.com/1/appKey/generate

The CALLBACK_DOMAIN is included as you need to give a fully-qualified domain to the Trello API, and it’s not always possible to infer what that might be - for instance when developing locally, you will need a tunnel from your machine out onto the web using something like ngrok.

When managing hooks via the Trello API a third key is required, and this is user specific - the admin site has a link next to the auth_token field on the form for creating a new Webhook. This uses the Trello API client.js to perform the Oauth dance - and supplies the user token. All webhooks are registered against a user token. That’s how it works. (NB you can pass any user tokens you have lying around to the sync_webhooks command and it will check Trello for any existing webhooks registered with those tokens.)

Tests

Ahem, there aren’t any at the moment. 0% coverage, use at your own risk. (I will get round to it at some point.)

Setup

The app is available on PyPI as django-trello-webhooks, so install with pip:

$ pip install django-trello-webhooks

Further Developments

• Write some tests

• Better integration with the Trello API

• Handle user auth token expiry properly

• Integration with Heroku’s “Deploy to Heroku” button

Contributing

Usual rules apply - fork, send pull request. Please try and adhere to the existing coding style - it may not be your style, but it’s the project’s style, so PRs will be rejected if they ‘smell bad’. Specifically, given that this is an app that is pushing data over the wire, and therefore hard to debug - lots of logging, and lots of comments. Seriously. Lots.

Licence

MIT (see LICENCE file)

Dependencies

The core Trello API integration is done using py-trello from Richard Kolkovich (@sarumont), so thanks to him for that. He naturally relies on requests from Kenneth Reitz, as well as request-oauthlib, so thanks to anyone involved with either of those.

Addenda

The webhook API works on the concept of a Trello model id. This refers to the object being watched - and could be a Board, a List, a Card etc. Getting these ids is a bit of a pain, to put it mildly, so I would strongly recommend using the excellent Trello Explorer app from Harald Wartig (@hwartig).

I would also recommend the use of ngrok to expose your local Django dev server during development.

As for development itself - use virtualenv, install dependencies from requirements.txt and set up environment variables. If that doesn’t mean anything to you - I’m afraid you have a lot to learn.