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A coroutine oriented web framework featuring: Mongrel2, Gevent (or Eventlet), ZeroMQ and DictShield
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brubeck
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README.md
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README.md

What Is Brubeck?

Brubeck is a flexible Python web framework that aims to make the process of building scalable web services easy.

The Brubeck model resembles what companies build when they operate at large scale, but working with it will feel like what you're used to from other frameworks.

  • No confusing callbacks
  • No database opinions
  • Built-in distributed load balancing

Example: Hello World

This is a whole Brubeck application.

class DemoHandler(WebMessageHandler):
    def get(self):
        self.set_body('Hello world')
        return self.render()

urls = [(r'^/', DemoHandler)]
mongrel2_pair = ('ipc://127.0.0.1:9999', 'ipc://127.0.0.1:9998')

app = Brubeck(mongrel2_pair=mongrel2_pair,
              handler_tuples=urls)
app.run()

Features

Brubeck gets by with a little help from its friends:

  • Mongrel2: lean & fast, asynchronous web serving
  • DictShield: data modeling & validation with no database opinions
  • ZeroMQ: fast messaging & supports most languages
  • Eventlet: non-blocking I/O, coroutines & implicit scheduling
  • Gevent: like eventlet, but uses libevent

Please also see this completely unscientific comparison of Brubeck and Tornado:

Complete Example: Listsurf

Listsurf is a simple to way to save links. Yeah... another delicious clone!

It serves as a basic demonstration of what a complete site looks like when you build with Brubeck. It has authentication with secure cookies, offers a JSON API, uses Jinja2 for templating, Eventlet for coroutines and stores data in MongoDB.

Closer Look At The Code

In this section we'll discuss writing a request handler, adding user authentication and rendering pages with templates.

Handling Requests

The framework can be used for different requirements. It can be lean and lightweight for high throughput or you can fatten it up and use it for rendering pages in a database backed CMS.

The general architecture of the system is to map requests for a specific URL to some callable for processing the request. The configuration attempts to match handlers to URL's by inspecting a list of (url pattern, callable) tuples. First regex to match provides the callable.

Some people like to use classes as handlers. Some folks prefer to use functions. Brubeck supports both.

MessageHandler Classes

When a class model is used, the class will be instantiated for the life of the request and then thrown away. This keeps our memory requirements nice and light.

Brubeck's MessageHandler design is similar to what you see in Tornado, or web.py.

To answer HTTP GET requests, implement get() on a WebMessageHandler instance.

class DemoHandler(WebMessageHandler):
    def get(self):
        self.set_body('Take five!')
        return self.render()

Then we add DemoHandler to the routing config and instantiate a Brubeck instance.

urls = [(r'^/brubeck', DemoHandler)]
config = {
    'handler_tuples': urls,
    ...
}

Brubeck(**config).run()

Notice the url regex is ^/brubeck. This will put our handler code on http://hostname/brubeck.

Functions and Decorators

If you'd prefer to just use a simple function, you instantiate a Brubeck instance and wrap your function with the add_route decorator.

Your function will be given two arguments. First, is the application itself. This provides the function with a hook almost all the information it might need. The second argument, the message, provides all the information available about the request.

That looks like this:

app = Brubeck(mongrel2_pair=('ipc://127.0.0.1:9999', 
                             'ipc://127.0.0.1:9998'))

@app.add_route('^/brubeck', method='GET')
def foo(application, message):
    return http_response('Take five!', 200, 'OK', {})

app.run()

Templates

Brubeck currently supports Jinja2 or Tornado templates.

Template support is contained in brubeck.templates as rendering mixins. Each Mixin will attach a render_template function to your handler and overwrite the default render_error to produce templated errors messages.

Using a template system is then as easy as calling render_template with the template filename and some context, just like you're used to.

Jinja2

Using Jinja2 template looks like this.

from brubeck.templating import Jinja2Rendering

class DemoHandler(WebMessageHandler, Jinja2Rendering):
    def get(self):
        context = {
            'name': 'J2 D2',
        }
        return self.render_template('success.html', **context)

Tornado

Tornado templates are supported by the TornadoRendering mixin. The code looks virtually the same to keep mixing template systems lightweight.

from brubeck.templating import TornadoRendering

class DemoHandler(WebMessageHandler, TornadoRendering):
    ...

Template Loading

In addition to using a rendering mixin, you need to provide the path to your templates.

That looks like this:

from brubeck.templating import load_jinja2_env

config = {
    template_loader=load_jinja2_env('./templates/jinja2')
    ...
}

Using a function here keeps the config lightweight.

Custom Rendering

If you have something else in mind, you'll be glad to know template_loader can be any callable that loads a rendering environment. Brubeck calls this during initialization and attaches the output to self.application.template_env.

The current convention is for handlers to provide a render_template and render_error function. These functions typically use self.application.template_env to render request specific data.

Auth

Authentication can be provided by decorating functions with the @web_authenticated decorator. This decorator expects the handler to have a current_user property that returns either an authenticated User model or None.

The UserHandlingMixin provides functionality for authenticating a user and creating the current_user property.

The work that's required will depend on how you build your system. The authentication framework uses a DictShield Document to create the User model, so you can implement a database query or check user information in a sorted CSV. Either way, you still get the authentication framework you need.

In practice, this is what your code looks like.

from brubeck.auth import web_authenticated, UserHandlingMixin

class DemoHandler(WebMessageHandler, UserHandlingMixin):
    @web_authenticated
    def post(self):
        ...

The User model in brubeck.auth will probably serve as a good basis for your needs. A Brubeck user looks roughly like below.

class User(Document):
    """Bare minimum to have the concept of a User.
    """
    username = StringField(max_length=30, required=True)
    email = EmailField(max_length=100)
    password = StringField(max_length=128)
    is_active = BooleanField(default=False)
    last_login = LongField(default=curtime)
    date_joined = LongField(default=curtime)        
    ...

Database Connections

Database connectivity is provided in the form of a db_conn member on the MessageHandler instances when a db_conn flag is passed to the Brubeck instance.

That looks like this:

config = {
    'db_conn': db_conn,
    ...
}

app = Brubeck(**config)

For people using MessageHandler instances, the database connection is available as self.db_conn.

For people using the function and decorator approach, you can get the database connection off the application argument, application.db_conn.

Query code then looks like this with the database connection as the first argument.

user = load_user(self.db_conn, username='jd')

Secure Cookies

If you need a session to persist, you can use Brubeck's secure cookies to track users.

You first add the cookie secret to your Brubeck config.

config = {
    'cookie_secret': 'OMGSOOOOSECRET',
    ...
}

Then retrieve the cookie value by passing the application's secret key into the get_cookie function.

# Try loading credentials from secure cookie
user_id = self.get_cookie('user_id',
                          secret=self.application.cookie_secret)

What you do from there is up to you, but you'll probably be loading the user_id from a database or cache to get the rest of the account info.

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