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Added a 'Why WSGI?' section to the WSGI server page. WIP.
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‎feeds/all.atom.xml‎

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<?xml version="1.0" encoding="utf-8"?>
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<feed xmlns="http://www.w3.org/2005/Atom"><title>Matt Makai</title><link href="http://www.fullstackpython.com/" rel="alternate"></link><link href="http://www.fullstackpython.com/feeds/all.atom.xml" rel="self"></link><id>http://www.fullstackpython.com/</id><updated>2014-02-16T09:22:08Z</updated></feed>
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<feed xmlns="http://www.w3.org/2005/Atom"><title>Matt Makai</title><link href="http://www.fullstackpython.com/" rel="alternate"></link><link href="http://www.fullstackpython.com/feeds/all.atom.xml" rel="self"></link><id>http://www.fullstackpython.com/</id><updated>2014-02-16T16:47:16Z</updated></feed>

‎source/content/pages/wsgi-servers.rst‎

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:slug: wsgi-servers
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:sort-order: 07
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A `Web Server Gateway Interface <http://wsgi.readthedocs.org/en/latest/>`_
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(WSGI) server implements the web server side of the WSGI interface for
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running Python web applications. The WSGI standard v1.0 is specified in
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`PEP 0333 <http://www.python.org/dev/peps/pep-0333/>`_. As of September 2010,
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WSGI v1.0 is superseded by
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A `Web Server Gateway Interface <http://wsgi.readthedocs.org/en/latest/>`_
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(WSGI) server implements the web server side of the WSGI interface for
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running Python web applications. The WSGI standard v1.0 is specified in
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`PEP 0333 <http://www.python.org/dev/peps/pep-0333/>`_. As of September 2010,
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WSGI v1.0 is superseded by
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`PEP 3333 <http://www.python.org/dev/peps/pep-3333/>`_, which defines the
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v1.0.1 WSGI standard.
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:class: technical-diagram
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A web server's configuration specifies what requests should be passed to
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the WSGI server to process. Once a request is processed and generated by the
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WSGI server, the response is passed back through the web server and onto
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the browser. For example, this Nginx web server's configuration specifics
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Nginx should handle static assets (such as images, JavaScript, and CSS
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the WSGI server to process. Once a request is processed and generated by the
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WSGI server, the response is passed back through the web server and onto
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the browser. For example, this Nginx web server's configuration specifics
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Nginx should handle static assets (such as images, JavaScript, and CSS
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files) under the /static directory and pass all other requests to the WSGI
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server running on port 8000::
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# nginx should serve up static files and never send to the WSGI server
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location /static {
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autoindex on;
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autoindex on;
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alias /srv/www/assets;
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}
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* what WSGI stands for (Web Server Gateway Inteface)
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* that a WSGI container is a separate running process that runs on a
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* that a WSGI container is a separate running process that runs on a
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different port than your web server
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* your web server is configured to pass requests to the WSGI container which
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runs your web application, then pass the response (in the form of HTML)
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runs your web application, then pass the response (in the form of HTML)
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back to the requester
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If you're using a standard web framework such as Django, Flask, or
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If you're using a standard web framework such as Django, Flask, or
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Bottle, or almost any other current Python framework, you don't need to worry
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about how frameworks implement the application side of the WSGI standard.
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Likewise, if you're using a standard WSGI container such as Green Unicorn,
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uWSGI, mod_wsgi, or gevent, you can get them running without worrying about
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how they implement the WSGI standard.
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how they implement the WSGI standard.
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However, knowing the WSGI standard and how these frameworks and containers
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implement WSGI should be on your learning checklist though as you become
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However, knowing the WSGI standard and how these frameworks and containers
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implement WSGI should be on your learning checklist though as you become
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a more experienced Python web developer.
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Why WSGI?
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---------
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Understanding the purpose of WSGI, and WSGI servers, is just as important as
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understanding their implementation. Why not just point a web server directly at
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your application?
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There are a couple of reasons:
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* **WSGI gives you flexibility.** Because the WSGI standard has been adopted
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by all Python application frameworks and many web servers, it is trivial for
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an application developer to swap out components of their stack for others.
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Switching web servers, WSGI servers and even frameworks becomes easy, because
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the configuration pattern is the same regardless of whether you are using
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NGINX, Gunicorn and Django or Apache, mod_wsgi and Flask. From `PEP 3333 <http://www.python.org/dev/peps/pep-3333/>`_:
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The availability and widespread use of such an API in web servers for Python
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[...] would separate choice of framework from choice of web server, freeing
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users to choose a pairing that suits them, while freeing framework and
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server developers to focus on their preferred area of specialization.
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* **WSGI servers promote scaling.** If you want to serve thousands of requests
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for dynamic content at once, relying on your application framework to smoothly
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handle the traffic is a bad idea. Most app frameworks don't focus on serving
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lots of concurrent requests gracefully. Rather, that job is left up to the WSGI
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server. It will handle processing requests from the web server and deciding
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how to communicate them to your application framework's process.
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TODO: go into more detail about this
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WSGI servers are designed with scaling in mind, and therefore their infrastructure
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is better suited to handling high traffic volume than directly exposing your
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application to the web.
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WSGI Resources
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--------------
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`PEP 0333 WSGI v1.0 <http://www.python.org/dev/peps/pep-0333/>`_
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`PEP 0333 WSGI v1.0 <http://www.python.org/dev/peps/pep-0333/>`_
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and
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`PEP 3333 WSGI v1.0.1 <http://www.python.org/dev/peps/pep-3333/>`_
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`PEP 3333 WSGI v1.0.1 <http://www.python.org/dev/peps/pep-3333/>`_
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specifications.
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`Green Unicorn <http://gunicorn.org/>`_,
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`Green Unicorn <http://gunicorn.org/>`_,
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`mod_wsgi <http://code.google.com/p/modwsgi/>`_,
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`uWSGI <https://github.com/unbit/uwsgi-docs>`_, and
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`gevent <http://www.gevent.org/>`_ are common WSGI server implementations.
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`Complete single server Django stack tutorial <http://www.apreche.net/complete-single-server-django-stack-tutorial/>`_ is thorough and informative for
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non-paas hosting choices.
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This detailed post entitled
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`The Beautiful Simplicity of an nginx and uWSGI Deployments <http://bartek.im/blog/2012/07/08/simplicity-nginx-uwsgi-deployment.html>`_
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is great reading for understanding Nginx and uWSGI configurations.
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This detailed post entitled
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`The Beautiful Simplicity of an nginx and uWSGI Deployments <http://bartek.im/blog/2012/07/08/simplicity-nginx-uwsgi-deployment.html>`_
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is great reading for understanding Nginx and uWSGI configurations.
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‎wsgi-servers.html‎

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<p>However, knowing the WSGI standard and how these frameworks and containers
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implement WSGI should be on your learning checklist though as you become
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a more experienced Python web developer.</p>
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<div class="section" id="why-wsgi">
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<h2>Why WSGI?</h2>
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<p>Understanding the purpose of WSGI, and WSGI servers, is just as important as
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understanding their implementation. Why not just point a web server directly at
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your application?
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There are a couple of reasons:</p>
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<ul>
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<li><p class="first"><strong>WSGI gives you flexibility.</strong> Because the WSGI standard has been adopted
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by all Python application frameworks and many web servers, it is trivial for
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an application developer to swap out components of their stack for others.
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Switching web servers, WSGI servers and even frameworks becomes easy, because
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the configuration pattern is the same regardless of whether you are using
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NGINX, Gunicorn and Django or Apache, mod_wsgi and Flask. From <a class="reference external" href="http://www.python.org/dev/peps/pep-3333/">PEP 3333</a>:</p>
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<blockquote>
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<p>The availability and widespread use of such an API in web servers for Python
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[...] would separate choice of framework from choice of web server, freeing
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users to choose a pairing that suits them, while freeing framework and
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server developers to focus on their preferred area of specialization.</p>
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</blockquote>
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</li>
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<li><p class="first"><strong>WSGI servers promote scaling.</strong> If you want to serve thousands of requests
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for dynamic content at once, relying on your application framework to smoothly
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handle the traffic is a bad idea. Most app frameworks don't focus on serving
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lots of concurrent requests gracefully. Rather, that job is left up to the WSGI
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server. It will handle processing requests from the web server and deciding
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how to communicate them to your application framework's process.</p>
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<p>TODO: go into more detail about this</p>
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<p>WSGI servers are designed with scaling in mind, and therefore their infrastructure
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is better suited to handling high traffic volume than directly exposing your
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application to the web.</p>
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</li>
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</ul>
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</div>
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<div class="section" id="wsgi-resources">
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<h2>WSGI Resources</h2>
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<p><a class="reference external" href="http://www.python.org/dev/peps/pep-0333/">PEP 0333 WSGI v1.0</a>

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