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gunicorn ‘Green Unicorn’ is a WSGI HTTP Server for UNIX handle fast clients and sleepy application.

This is a port of Unicorn ( in Python. Meet us on #gunicorn irc channel on Freenode.


Gunicorn requires Python 2.5 or newer (Python 3.x will be supported soon).

Install from sources:

$ python install

Or from Pypi:

$ easy_install -U gunicorn

If you want to handle sleepy applications you will need to install Eventlet or Gevent.

To install eventlet:

$ easy_install -U eventlet

Replace eventlet by gevent if you want to use gevent. You can now launch gunicorn with Eventlet or Gevent arbiter, see Gunicorn usage for more information.

If you encounter errors when compiling the extensions for gevent or eventlet you probably need to install a newer version of libev.


$ gunicorn --help
Usage: gunicorn [OPTIONS] [APP_MODULE]

  -c CONFIG, --config=CONFIG
                        Config file. [none]
  -b BIND, --bind=BIND  Adress to listen on. Ex. or
  -w WORKERS, --workers=WORKERS
                        Number of workers to spawn. [1]
  -a ARBITER, --arbiter=ARBITER
                        gunicorn arbiter entry point or module
                        set the background PID FILE
  -D, --daemon          Run daemonized in the background.
  -m UMASK, --umask=UMASK
                        Define umask of daemon process
  -u USER, --user=USER  Change worker user
  -g GROUP, --group=GROUP
                        Change worker group
  -n APP_NAME, --name=APP_NAME
                        Application name
  --log-level=LOGLEVEL  Log level below which to silence messages. [info]
  --log-file=LOGFILE    Log to a file. - equals stdout. [-]
  -d, --debug           Debug mode. only 1 worker.
  --version             show program's version number and exit
  -h, --help            show this help message and exit

Example with test app:

$ cd examples
$ gunicorn --workers=2 test:app

Django projects

For django projects use the gunicorn_django command:

$ cd yourdjangoproject
$ gunicorn_django --workers=2

or use run_gunicorn command.

add gunicorn to INSTALLED_APPS in the settings file:


Then run:

python run_gunicorn

Paste-compatible projects

For paste-compatible projects (like Pylons, TurboGears 2, …) use the gunicorn_paste command:

$ cd your pasteproject
$ gunicorn_paste --workers=2 development.ini

or usual paster command:

$ cd your pasteproject
$ paster serve development.ini workers=2

In last case don’t forget to add a server section for gunicorn. Here is an example that use gunicorn as main server:

use = egg:gunicorn#main
host =
port = 5000

Kernel Parameters

There are various kernel parameters that you might want to tune in order to deal with a large number of simultaneous connections. Generally these should only affect sites with a large number of concurrent requests and apply to any sort of network server you may be running. They’re listed here for ease of reference.

The commands listed are tested under Mac OS X 10.6. Your flavor of Unix may use slightly different flags. Always reference the appropriate man pages if uncertain.

Increasing the File Descriptor Limit

One of the first settings that usually needs to be bumped is the maximum number of open file descriptors for a given process. For the confused out there, remember that Unices treat sockets as files.

$ sudo ulimit -n 1024

Increasing the Listen Queue Size

Listening sockets have an associated queue of incoming connections that are waiting to be accepted. If you happen to have a stampede of clients that fill up this queue new connections will eventually start getting dropped.

$ sudo sysctl -w kern.ipc.somaxconn="1024"

Widening the Ephemeral Port Range

After a socket is closed it eventually enters the TIME_WAIT state. This can become an issue after a prolonged burst of client activity. Eventually the ephemeral port range is used up which can cause new connections to stall while they wait for a valid port.

This setting is generally only required on machines that are being used to test a network server.

$ sudo sysctl -w net.inet.ip.portrange.first="8048"

Check this article for more information on ephemeral ports.

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