This chapter presents a few use cases, to give you an idea on how to use Circus in your environment.
Running a WSGI application with Circus is quite interesting because you can watch & manage your web workers using circus-top, circusctl or the Web interface.
This is made possible by using Circus sockets. See Circus stack v.s. Classical stack.
Let’s take an example with a minimal Pyramid application:
from pyramid.config import Configurator
from pyramid.response import Response
def hello_world(request):
return Response('Hello %(name)s!' % request.matchdict)
config = Configurator()
config.add_route('hello', '/hello/{name}')
config.add_view(hello_world, route_name='hello')
application = config.make_wsgi_app()
Save this script into an app.py file, then install those projects:
$ pip install Pyramid
$ pip install chaussette
Next, make sure you can run your Pyramid application using the chaussette console script:
$ chaussette app.application
Application is <pyramid.router.Router object at 0x10a4d4bd0>
Serving on localhost:8080
Using <class 'chaussette.backend._waitress.Server'> as a backend
And check that you can reach it by visiting http://localhost:8080/hello/tarek
Now that your application is up and running, let’s create a Circus configuration file:
[circus]
check_delay = 5
endpoint = tcp://127.0.0.1:5555
pubsub_endpoint = tcp://127.0.0.1:5556
stats_endpoint = tcp://127.0.0.1:5557
[watcher:webworker]
cmd = chaussette --fd $(circus.sockets.webapp) app.application
use_sockets = True
numprocesses = 3
[socket:webapp]
host = 127.0.0.1
port = 8080
This file tells Circus to bind a socket on port 8080 and run chaussette workers on that socket – by passing its fd.
Save it to server.ini and try to run it using circusd
$ circusd server.ini
[INFO] Starting master on pid 8971
[INFO] sockets started
[INFO] circusd-stats started
[INFO] webapp started
[INFO] Arbiter now waiting for commands
Make sure you still get the app on http://localhost:8080/hello/tarek.
Congrats ! you have a WSGI application running 3 workers.
You can run the The Web Console or the Command-line tools, and enjoy Circus management.
Running a Django application is done exactly like running a WSGI application. Use the PYTHONPATH to import the directory the project is in, the directory that contains the directory that has settings.py in it (with Django 1.4+ this directory has manage.py in it)
[socket:dwebapp]
host = 127.0.0.1
port = 8080
[watcher:dwebworker]
cmd = chaussette --fd $(circus.sockets.dwebapp) dproject.wsgi.application
use_sockets = True
numprocesses = 2
[env:dwebworker]
PYTHONPATH = /path/to/parent-of-dproject
If you need to pass the DJANGO_SETTINGS_MODULE for a backend worker for example, you can pass that also though the env configation option:
[watcher:dbackend]
cmd = /path/to/script.py
numprocesses=3
[env:dbackend]
PYTHONPATH = /path/to/parent-of-dproject
DJANGO_SETTINGS_MODULE=dproject.settings
See http://chaussette.readthedocs.org for more about chaussette.