Chaussette WSGI Server


Chaussette is a WSGI server you can use to run your Python WSGI applications.

The particularity of Chaussette is that it can either bind a socket on a port like any other server does or run against already opened sockets.

That makes Chaussette the best companion to run a WSGI or Django stack under a process and socket manager, such as Circus or Supervisor.

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You can run a plain WSGI application, a Django application, or a Paste application. To get all options, just run chaussette –help.

Running a plain WSGI application

Chaussette provides a console script you can launch against a WSGI application, like any WSGI server out there:

$ chaussette mypackage.myapp
Application is <function myapp at 0x104d97668>
Serving on localhost:8080
Using <class chaussette.backend._wsgiref.ChaussetteServer at 0x104e58d50> as a backend

Running a Django application

Chaussette allows you to run a Django project. You just need to provide the Python import path of the WSGI application, commonly located in the Django project’s file. For further information about how the file should look like see the Django documentation.

Here’s an example:

$ chaussette --backend gevent mysite.wsgi.application
Application is <django.core.handlers.wsgi.WSGIHandler object at 0x10ec3f350>
Serving on localhost:8080
Using <class 'chaussette.backend._gevent.Server'> as a backend

Running a Python Paste application

Chaussette will let you run a project based on a Python Paste configuration file.

You just need to use to provide the path to the configuration file in the application, prefixed with paste:

Here’s an example:

$ chaussette paste:path/to/configuration.ini
$ Application is <mozsvc.middlewares.CatchErrorMiddleware object at 0x10d4fdad0>
$ Serving on localhost:8080
$ Using <class chaussette.backend._wsgiref.ChaussetteServer at 0x10cc7e668> as a backend

Using Chaussette in Circus

The typical use case is to run Chaussette processes under a process and socket manager. Chaussette was developed to run under Circus, which takes care of binding the socket and spawning Chaussette processes.

To run your WSGI application using Circus, define a socket section in your configuration file, then add a Chaussette watcher.

Minimal example:

endpoint = tcp://
pubsub_endpoint = tcp://
stats_endpoint = tcp://

cmd = chaussette --fd $(circus.sockets.web) --backend meinheld
use_sockets = True
numprocesses = 5

host =
port = 8000

When Circus runs, it binds a socket on the 8000 port and passes the file descriptor value to the Chaussette process, by replacing ${socket:web} by the file number value.

Using Chaussette in Supervisor

Supervisor includes a socket manager since version 3.0a7, released in 2009. It was originally developed to support FastCGI processes and thus the configuration section is called fcgi-program. Despite the name, it is not tied to the FastCGI protocol. Supervisor can bind the socket and then spawn Chaussette processes.

To run your WSGI application using Supervisor, define an fcgi-program section in your configuration file.

Minimal example:

logfile = /tmp/supervisord.log

port =

serverurl =

supervisor.rpcinterface_factory = supervisor.rpcinterface:make_main_rpcinterface

command = chaussette --fd 0 --backend meinheld
process_name = %(program_name)s_%(process_num)s
numprocs = 5
socket = tcp://

Notice the --fd 0 argument to chaussette. Each fcgi-program section defines its own socket and the file descriptor is always 0. See the Supervisor manual for detailed information.

Supervisor will create the socket before spawning the first Chaussette child process. When the last child exits, Supervisor will close the socket.


Chaussette is just a bit of glue code on the top of existing WSGI servers, and is organized around back ends.

By default Chaussette uses a pure Python implementation based on wsgiref, but it also provides more efficient back ends. Most of them are for Python 2 only, but Chaussette can be used under Python 3 with a few of them - marked in the list below:

You can select your backend by using the –backend option and providing its name.

For some backends, you need to make sure the corresponding libraries are installed:

If you want to add your favorite WSGI Server as a backend to Chaussette, or if you think you can make one of the backend Python 3 compatible, send me an e-mail !

If you curious about how each on of those backends performs, you can read:

Rationale and Design

Most WGSI servers out there provide advanced features to scale your web applications, like multi-threading or multi-processing. Depending on the project, the process management features, like respawning processes that die, or adding new ones on the fly, are not always very advanced.

On the other hand, tools like Circus and Supervisor have more advanced features to manage your processes, and are able to manage sockets as well.

The goal of Chaussette is to delegate process and socket management to its parent process and just focus on serving requests.

Using a pre-fork model, the process manager binds a socket. It then forks Chaussette child processes that accept connections on that socket.

For more information about this design, read :