robinhood/thorn

Python Stream Processing

About

Thorn is a webhook framework for Python, focusing on flexibility and ease of use, both when getting started and when maintaining a production system.

The goal is for webhooks to thrive on the web, by providing Python projects with an easy solution to implement them and keeping a repository of patterns evolved by the Python community.

• Simple

  Add webhook capabilities to your database models using a single decorator, including filtering for specific changes to the model.

• Flexible

  All Thorn components are pluggable, reusable and extendable.

• Scalable

  Thorn can perform millions of HTTP requests every second by taking advantage of Celery for asynchronous processing.

What are webhooks?

A webhook is a fancy name for an HTTP callback.

Users and other services can subscribe to events happening in your system by registering a URL to be called whenever the event occurs.

The canonical example would be GitHub where you can register URLs to be called whenever a new change is committed to your repository, a new bugtracker issue is created, someone publishes a comment, and so on.

Another example is communication between internal systems, traditionally dominated by complicated message consumer daemons, using webhooks is an elegant and REST friendly way to implement event driven systems, requiring only a web-server (and optimally a separate service to dispatch the HTTP callback requests).

Webhooks are also composable, so you can combine multiple HTTP callbacks to form complicated workflows, executed as events happen across multiple systems.

In use

Notable examples of webhooks in use are:

Example

This example adds four webhook events to the Article model of an imaginary blog engine:

from django.urls import reverse
from thorn import ModelEvent, webhook_model

@webhook_model   # <--- activate webhooks for this model
class Article(models.Model):
    uuid = models.UUIDField()
    title = models.CharField(max_length=100)
    body = models.TextField()

    class webhooks:
        on_create = ModelEvent('article.created')
        on_change = ModelEvent('article.changed'),
        on_delete = ModelEvent('article.removed'),
        on_publish = ModelEvent(
            'article.published',
            state__eq='PUBLISHED',
        ).dispatches_on_change(),

    def get_absolute_url(self):
        return reverse('article:detail', kwargs={'uuid': self.uuid})

Users can now subscribe to the four events individually, or all of them by subscribing to article.*, and will be notified every time an article is created, changed, removed or published:

$ curl -X POST                                                      \
> -H "Authorization: Bearer <secret login token>"                   \
> -H "Content-Type: application/json"                               \
> -d '{"event": "article.*", "url": "https://e.com/h/article?u=1"}' \
> http://example.com/hooks/

The API is expressive, so may require you to learn more about the arguments to understand it fully. Luckily it's all described in the Events Guide for you to consult after reading the quick start tutorial.

What do I need?

Thorn currently only supports Django, and an API for subscribing to events is only provided for Django REST Framework.

Extending Thorn is simple so you can also contribute support for your favorite frameworks.

For dispatching web requests we recommend using Celery, but you can get started immediately by dispatching requests locally.

Using Celery for dispatching requests will require a message transport like RabbitMQ or Redis.

You can also write custom dispatchers if you have an idea for efficient payload delivery, or just want to reuse a technology you already deploy in production.

Quick Start

Go immediately to the django-guide guide to get started using Thorn in your Django projects.

If you are using a different web framework, please consider contributing to the project by implementing a new environment type.

Alternatives

Thorn was inspired by multiple Python projects:

• dj-webhooks
• django-rest-hooks
• durian

Installation

Installing the stable version

You can install thorn either via the Python Package Index (PyPI) or from source.

To install using pip,:

$ pip install -U thorn

Downloading and installing from source

Download the latest version of thorn from http://pypi.python.org/pypi/thorn/

You can install it by doing the following,:

$ tar xvfz thorn-0.0.0.tar.gz
$ cd thorn-0.0.0
$ python setup.py build
# python setup.py install

The last command must be executed as a privileged user if you are not currently using a virtualenv.

Using the development version

With pip

You can install the latest snapshot of thorn using the following pip command:

$ pip install https://github.com/robinhood/thorn/zipball/master#egg=thorn

Getting Help

Mailing list

For discussions about the usage, development, and future of Thorn, please join the thorn-users mailing list.

IRC

Come chat with us on IRC. The #thorn channel is located at the Freenode network.

Bug tracker

If you have any suggestions, bug reports or annoyances please report them to our issue tracker at https://github.com/robinhood/thorn/issues/

Contributing

Development of Thorn happens at GitHub: https://github.com/robinhood/thorn

You are highly encouraged to participate in the development of thorn. If you don't like GitHub (for some reason) you're welcome to send regular patches.

Be sure to also read the Contributing to Thorn section in the documentation.

License

This software is licensed under the New BSD License. See the LICENSE file in the top distribution directory for the full license text.