.. _deploying-wsgi-standalone: Standalone WSGI Containers ========================== There are popular servers written in Python that contain WSGI applications and serve HTTP. These servers stand alone when they run; you can proxy to them from your web server. Note the section on :ref:`deploying-proxy-setups` if you run into issues. Gunicorn -------- `Gunicorn`_ 'Green Unicorn' is a WSGI HTTP Server for UNIX. It's a pre-fork worker model ported from Ruby's Unicorn project. It supports both `eventlet`_ and `greenlet`_. Running a Flask application on this server is quite simple:: gunicorn myproject:app `Gunicorn`_ provides many command-line options -- see ``gunicorn -h``. For example, to run a Flask application with 4 worker processes (``-w 4``) binding to localhost port 4000 (``-b 127.0.0.1:4000``):: gunicorn -w 4 -b 127.0.0.1:4000 myproject:app .. _Gunicorn: http://gunicorn.org/ .. _eventlet: http://eventlet.net/ .. _greenlet: http://greenlet.readthedocs.org/en/latest/ Gevent ------- `Gevent`_ is a coroutine-based Python networking library that uses `greenlet`_ to provide a high-level synchronous API on top of `libevent`_ event loop:: from gevent.wsgi import WSGIServer from yourapplication import app http_server = WSGIServer(('', 5000), app) http_server.serve_forever() .. _Gevent: http://www.gevent.org/ .. _greenlet: http://greenlet.readthedocs.org/en/latest/ .. _libevent: http://libevent.org/ Twisted Web ----------- `Twisted Web`_ is the web server shipped with `Twisted`_, a mature, non-blocking event-driven networking library. Twisted Web comes with a standard WSGI container which can be controlled from the command line using the ``twistd`` utility:: twistd web --wsgi myproject.app This example will run a Flask application called ``app`` from a module named ``myproject``. Twisted Web supports many flags and options, and the ``twistd`` utility does as well; see ``twistd -h`` and ``twistd web -h`` for more information. For example, to run a Twisted Web server in the foreground, on port 8080, with an application from ``myproject``:: twistd -n web --port 8080 --wsgi myproject.app .. _Twisted: https://twistedmatrix.com/ .. _Twisted Web: https://twistedmatrix.com/trac/wiki/TwistedWeb .. _deploying-proxy-setups: Proxy Setups ------------ If you deploy your application using one of these servers behind an HTTP proxy you will need to rewrite a few headers in order for the application to work. The two problematic values in the WSGI environment usually are ``REMOTE_ADDR`` and ``HTTP_HOST``. You can configure your httpd to pass these headers, or you can fix them in middleware. Werkzeug ships a fixer that will solve some common setups, but you might want to write your own WSGI middleware for specific setups. Here's a simple nginx configuration which proxies to an application served on localhost at port 8000, setting appropriate headers: .. sourcecode:: nginx server { listen 80; server_name _; access_log /var/log/nginx/access.log; error_log /var/log/nginx/error.log; location / { proxy_pass http://127.0.0.1:8000/; proxy_redirect off; proxy_set_header Host $host; proxy_set_header X-Real-IP $remote_addr; proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for; } } If your httpd is not providing these headers, the most common setup invokes the host being set from ``X-Forwarded-Host`` and the remote address from ``X-Forwarded-For``:: from werkzeug.contrib.fixers import ProxyFix app.wsgi_app = ProxyFix(app.wsgi_app) .. admonition:: Trusting Headers Please keep in mind that it is a security issue to use such a middleware in a non-proxy setup because it will blindly trust the incoming headers which might be forged by malicious clients. If you want to rewrite the headers from another header, you might want to use a fixer like this:: class CustomProxyFix(object): def __init__(self, app): self.app = app def __call__(self, environ, start_response): host = environ.get('HTTP_X_FHOST', '') if host: environ['HTTP_HOST'] = host return self.app(environ, start_response) app.wsgi_app = CustomProxyFix(app.wsgi_app)