=========================
Serving WSGI Applications
=========================

.. module:: werkzeug

There are many ways to serve a WSGI application.  While you're developing it,
you usually don't want to have a full-blown webserver like Apache up and
running, but instead a simple standalone one.  Because of that Werkzeug comes
with a builtin development server.

The easiest way is creating a small ``start-myproject.py`` file that runs the
application using the builtin server::

    #!/usr/bin/env python
    # -*- coding: utf-8 -*-

    from werkzeug import run_simple
    from myproject import make_app

    app = make_app(...)
    run_simple('localhost', 8080, app, use_reloader=True)

You can also pass it the `extra_files` keyword argument with a list of
additional files (like configuration files) you want to observe.

.. autofunction:: run_simple

.. admonition:: Information

   The development server is not intended to be used on production systems.
   It was designed especially for development purposes and performs poorly
   under high load.  For deployment setups have a look at the
   :ref:`deployment` pages.

Virtual Hosts
-------------

Many web applications utilize multiple subdomains.  This can be a bit tricky
to simulate locally.  Fortunately there is the `hosts file`_ that can be used
to assign the local computer multiple names.

This allows you to call your local computer `yourapplication.local` and
`api.yourapplication.local` (or anything else) in addition to `localhost`.

You can find the hosts file on the following location:

    =============== ==============================================
    Windows         ``%SystemRoot%\system32\drivers\etc\hosts``
    Linux / OS X    ``/etc/hosts``
    =============== ==============================================

You can open the file with your favorite text editor and add a new name after
`localhost`::

    127.0.0.1       localhost yourapplication.local api.yourapplication.local

Save the changes and after a while you should be able to access the
development server on these host names as well.  You can use the
:ref:`routing` system to dispatch between different hosts or parse
:attr:`request.host` yourself.

Troubleshooting
---------------

On operating systems that support ipv6 and have it configured such as modern
Linux systems, OS X 10.4 or higher as well as Windows Vista some browsers can
be painfully slow if accessing your local server.  The reason for this is that
sometimes "localhost" is configured to be available on both ipv4 and ipv6 socktes
and some browsers will try to access ipv6 first and then ivp4.

At the current time the integrated webserver does not support ipv6 and ipv4 at
the same time and for better portability ipv4 is the default.

If you notice that the web browser takes ages to load the page there are two ways
around this issue.  If you don't need ipv6 support you can disable the ipv6 entry
in the `hosts file`_ by removing this line::

    ::1             localhost

Alternatively you can also disable ipv6 support in your browser.  For example
if Firefox shows this behavior you can disable it by going to ``about:config``
and disabling the `network.dns.disableIPv6` key.  This however is not
recommended as of Werkzeug 0.6.1!

Starting with Werkzeug 0.6.1, the server will now switch between ipv4 and
ipv6 based on your operating system's configuration.  This means if that
you disabled ipv6 support in your browser but your operating system is
preferring ipv6, you will be unable to connect to your server.  In that
situation, you can either remove the localhost entry for ``::1`` or
explicitly bind the hostname to an ipv4 address (`127.0.0.1`)

.. _hosts file: http://en.wikipedia.org/wiki/Hosts_file

SSL
---

.. versionadded:: 0.6

The builtin server supports SSL for testing purposes.  If an SSL context
is provided it will be used.  That means a server can either run in HTTP
or HTTPS mode, but not both.  This feature requires the Python OpenSSL
library.

The easiest way to enable SSL is to start the server in adhoc-mode.  In
that case Werkzeug will generate an SSL certificate for you::

    run_simple('localhost', 4000, application,
               ssl_context='adhoc')

The downside of this of course is that you will have to acknowledge the
certificate each time the server is reloaded.  You can generate a
certificate and key in advance and provide the SSL context when the server
is started::

    from OpenSSL import SSL
    ctx = SSL.Context(SSL.SSLv23_METHOD)
    ctx.use_privatekey_file('ssl.key')
    ctx.use_certificate_file('ssl.cert')
    run_simple('localhost', 4000, application, ssl_context=ctx)

A key and certificate can be created in advance using the openssl tool::

    $ openssl genrsa 1024 > ssl.key
    $ openssl req -new -x509 -nodes -sha1 -days 365 -key ssl.key > ssl.cert