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<div class="section" id="mod-wsgi-apache">
<span id="mod-wsgi-deployment"></span><h1>mod_wsgi (Apache)<a class="headerlink" href="#mod-wsgi-apache" title="Permalink to this headline">¶</a></h1>
<p>If you are using the <a class="reference external" href="http://httpd.apache.org/">Apache</a> webserver, consider using <a class="reference external" href="http://code.google.com/p/modwsgi/">mod_wsgi</a>.</p>
<div class="admonition-watch-out admonition ">
<p class="first admonition-title">Watch Out</p>
<p class="last">Please make sure in advance that any <tt class="docutils literal"><span class="pre">app.run()</span></tt> calls you might
have in your application file are inside an <tt class="docutils literal"><span class="pre">if</span> <span class="pre">__name__</span> <span class="pre">==</span>
<span class="pre">'__main__':</span></tt> block or moved to a separate file. Just make sure it’s
not called because this will always start a local WSGI server which
we do not want if we deploy that application to mod_wsgi.</p>
</div>
<div class="section" id="installing-mod-wsgi">
<h2>Installing <cite>mod_wsgi</cite><a class="headerlink" href="#installing-mod-wsgi" title="Permalink to this headline">¶</a></h2>
<p>If you don’t have <cite>mod_wsgi</cite> installed yet you have to either install it
using a package manager or compile it yourself. The mod_wsgi
<a class="reference external" href="http://code.google.com/p/modwsgi/wiki/QuickInstallationGuide">installation instructions</a> cover source installations on UNIX systems.</p>
<p>If you are using Ubuntu/Debian you can apt-get it and activate it as
follows:</p>
<div class="highlight-text"><div class="highlight"><pre># apt-get install libapache2-mod-wsgi
</pre></div>
</div>
<p>On FreeBSD install <cite>mod_wsgi</cite> by compiling the <cite>www/mod_wsgi</cite> port or by
using pkg_add:</p>
<div class="highlight-text"><div class="highlight"><pre># pkg_add -r mod_wsgi
</pre></div>
</div>
<p>If you are using pkgsrc you can install <cite>mod_wsgi</cite> by compiling the
<cite>www/ap2-wsgi</cite> package.</p>
<p>If you encounter segfaulting child processes after the first apache
reload you can safely ignore them. Just restart the server.</p>
</div>
<div class="section" id="creating-a-wsgi-file">
<h2>Creating a <cite>.wsgi</cite> file<a class="headerlink" href="#creating-a-wsgi-file" title="Permalink to this headline">¶</a></h2>
<p>To run your application you need a <cite>yourapplication.wsgi</cite> file. This file
contains the code <cite>mod_wsgi</cite> is executing on startup to get the application
object. The object called <cite>application</cite> in that file is then used as
application.</p>
<p>For most applications the following file should be sufficient:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="kn">from</span> <span class="nn">yourapplication</span> <span class="kn">import</span> <span class="n">app</span> <span class="k">as</span> <span class="n">application</span>
</pre></div>
</div>
<p>If you don’t have a factory function for application creation but a singleton
instance you can directly import that one as <cite>application</cite>.</p>
<p>Store that file somewhere that you will find it again (e.g.:
<cite>/var/www/yourapplication</cite>) and make sure that <cite>yourapplication</cite> and all
the libraries that are in use are on the python load path. If you don’t
want to install it system wide consider using a <a class="reference external" href="http://pypi.python.org/pypi/virtualenv">virtual python</a>
instance.</p>
</div>
<div class="section" id="configuring-apache">
<h2>Configuring Apache<a class="headerlink" href="#configuring-apache" title="Permalink to this headline">¶</a></h2>
<p>The last thing you have to do is to create an Apache configuration file
for your application. In this example we are telling <cite>mod_wsgi</cite> to
execute the application under a different user for security reasons:</p>
<div class="highlight-apache"><div class="highlight"><pre><span class="nt"><VirtualHost</span> <span class="s">*</span><span class="nt">></span>
<span class="nb">ServerName</span> example.com
<span class="nb">WSGIDaemonProcess</span> yourapplication <span class="k">user</span>=user1 <span class="k">group</span>=group1 threads=5
<span class="nb">WSGIScriptAlias</span> / <span class="sx">/var/www/yourapplication/yourapplication.wsgi</span>
<span class="nt"><Directory</span> <span class="s">/var/www/yourapplication</span><span class="nt">></span>
<span class="nb">WSGIProcessGroup</span> yourapplication
<span class="nb">WSGIApplicationGroup</span> %{GLOBAL}
<span class="nb">Order</span> deny,allow
<span class="nb">Allow</span> from <span class="k">all</span>
<span class="nt"></Directory></span>
<span class="nt"></VirtualHost></span>
</pre></div>
</div>
<p>For more information consult the <a class="reference external" href="http://code.google.com/p/modwsgi/wiki/">mod_wsgi wiki</a>.</p>
</div>
<div class="section" id="troubleshooting">
<h2>Troubleshooting<a class="headerlink" href="#troubleshooting" title="Permalink to this headline">¶</a></h2>
<p>If your application does not run, follow this guide to troubleshoot:</p>
<dl class="docutils">
<dt><strong>Problem:</strong> application does not run, errorlog shows SystemExit ignored</dt>
<dd>You have a <tt class="docutils literal"><span class="pre">app.run()</span></tt> call in your application file that is not
guarded by an <tt class="docutils literal"><span class="pre">if</span> <span class="pre">__name__</span> <span class="pre">==</span> <span class="pre">'__main__':</span></tt> condition. Either
remove that <a class="reference internal" href="../api.html#flask.Flask.run" title="flask.Flask.run"><tt class="xref py py-meth docutils literal"><span class="pre">run()</span></tt></a> call from the file and move it
into a separate <cite>run.py</cite> file or put it into such an if block.</dd>
<dt><strong>Problem:</strong> application gives permission errors</dt>
<dd>Probably caused by your application running as the wrong user. Make
sure the folders the application needs access to have the proper
privileges set and the application runs as the correct user
(<tt class="docutils literal"><span class="pre">user</span></tt> and <tt class="docutils literal"><span class="pre">group</span></tt> parameter to the <cite>WSGIDaemonProcess</cite>
directive)</dd>
<dt><strong>Problem:</strong> application dies with an error on print</dt>
<dd><p class="first">Keep in mind that mod_wsgi disallows doing anything with
<a class="reference external" href="http://docs.python.org/dev/library/sys.html#sys.stdout" title="(in Python v3.3)"><tt class="xref py py-data docutils literal"><span class="pre">sys.stdout</span></tt></a> and <a class="reference external" href="http://docs.python.org/dev/library/sys.html#sys.stderr" title="(in Python v3.3)"><tt class="xref py py-data docutils literal"><span class="pre">sys.stderr</span></tt></a>. You can disable this
protection from the config by setting the <cite>WSGIRestrictStdout</cite> to
<tt class="docutils literal"><span class="pre">off</span></tt>:</p>
<div class="highlight-apache"><div class="highlight"><pre><span class="nb">WSGIRestrictStdout</span> <span class="k">Off</span>
</pre></div>
</div>
<p>Alternatively you can also replace the standard out in the .wsgi file
with a different stream:</p>
<div class="last highlight-python"><div class="highlight"><pre><span class="kn">import</span> <span class="nn">sys</span>
<span class="n">sys</span><span class="o">.</span><span class="n">stdout</span> <span class="o">=</span> <span class="n">sys</span><span class="o">.</span><span class="n">stderr</span>
</pre></div>
</div>
</dd>
<dt><strong>Problem:</strong> accessing resources gives IO errors</dt>
<dd><p class="first">Your application probably is a single .py file you symlinked into
the site-packages folder. Please be aware that this does not work,
instead you either have to put the folder into the pythonpath the
file is stored in, or convert your application into a package.</p>
<p class="last">The reason for this is that for non-installed packages, the module
filename is used to locate the resources and for symlinks the wrong
filename is picked up.</p>
</dd>
</dl>
</div>
<div class="section" id="support-for-automatic-reloading">
<h2>Support for Automatic Reloading<a class="headerlink" href="#support-for-automatic-reloading" title="Permalink to this headline">¶</a></h2>
<p>To help deployment tools you can activate support for automatic
reloading. Whenever something changes the <cite>.wsgi</cite> file, <cite>mod_wsgi</cite> will
reload all the daemon processes for us.</p>
<p>For that, just add the following directive to your <cite>Directory</cite> section:</p>
<div class="highlight-apache"><div class="highlight"><pre><span class="nb">WSGIScriptReloading</span> <span class="k">On</span>
</pre></div>
</div>
</div>
<div class="section" id="working-with-virtual-environments">
<h2>Working with Virtual Environments<a class="headerlink" href="#working-with-virtual-environments" title="Permalink to this headline">¶</a></h2>
<p>Virtual environments have the advantage that they never install the
required dependencies system wide so you have a better control over what
is used where. If you want to use a virtual environment with mod_wsgi
you have to modify your <cite>.wsgi</cite> file slightly.</p>
<p>Add the following lines to the top of your <cite>.wsgi</cite> file:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="n">activate_this</span> <span class="o">=</span> <span class="s">'/path/to/env/bin/activate_this.py'</span>
<span class="nb">execfile</span><span class="p">(</span><span class="n">activate_this</span><span class="p">,</span> <span class="nb">dict</span><span class="p">(</span><span class="n">__file__</span><span class="o">=</span><span class="n">activate_this</span><span class="p">))</span>
</pre></div>
</div>
<p>This sets up the load paths according to the settings of the virtual
environment. Keep in mind that the path has to be absolute.</p>
</div>
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<h3><a href="../index.html">Table Of Contents</a></h3>
<ul>
<li><a class="reference internal" href="#">mod_wsgi (Apache)</a><ul>
<li><a class="reference internal" href="#installing-mod-wsgi">Installing <cite>mod_wsgi</cite></a></li>
<li><a class="reference internal" href="#creating-a-wsgi-file">Creating a <cite>.wsgi</cite> file</a></li>
<li><a class="reference internal" href="#configuring-apache">Configuring Apache</a></li>
<li><a class="reference internal" href="#troubleshooting">Troubleshooting</a></li>
<li><a class="reference internal" href="#support-for-automatic-reloading">Support for Automatic Reloading</a></li>
<li><a class="reference internal" href="#working-with-virtual-environments">Working with Virtual Environments</a></li>
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