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  <div class="section" id="wsgiapplicationgroup">
<h1>WSGIApplicationGroup<a class="headerlink" href="#wsgiapplicationgroup" title="Permalink to this headline">¶</a></h1>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">Description:</th><td class="field-body">Sets which application group WSGI application belongs to.</td>
</tr>
<tr class="field-even field"><th class="field-name">Syntax:</th><td class="field-body"><tt class="docutils literal"><span class="pre">WSGIApplicationGroup</span> <span class="pre">name</span></tt>
<tt class="docutils literal"><span class="pre">WSGIApplicationGroup</span> <span class="pre">%{GLOBAL}</span></tt>
<tt class="docutils literal"><span class="pre">WSGIApplicationGroup</span> <span class="pre">%{SERVER}</span></tt>
<tt class="docutils literal"><span class="pre">WSGIApplicationGroup</span> <span class="pre">%{RESOURCE}</span></tt>
<tt class="docutils literal"><span class="pre">WSGIApplicationGroup</span> <span class="pre">%{ENV:variable}</span></tt></td>
</tr>
<tr class="field-odd field"><th class="field-name">Default:</th><td class="field-body"><tt class="docutils literal"><span class="pre">WSGIApplicationGroup</span> <span class="pre">%{RESOURCE}</span></tt></td>
</tr>
<tr class="field-even field"><th class="field-name">Context:</th><td class="field-body">server config, virtual host, directory</td>
</tr>
</tbody>
</table>
<p>The <tt class="docutils literal"><span class="pre">WSGIApplicationGroup</span></tt> directive can be used to specify which
application group a WSGI application or set of WSGI applications belongs
to. All WSGI applications within the same application group will execute
within the context of the same Python sub interpreter of the process
handling the request.</p>
<p>Setting <tt class="docutils literal"><span class="pre">WSGIApplicationGroup</span></tt> doesn&#8217;t control what processes a request
is handled by, that is what the <tt class="docutils literal"><span class="pre">WSGIProcessGroup</span></tt> directive does. In
other words, the <tt class="docutils literal"><span class="pre">WSGIProcessGroup</span></tt> directive operates distinct from the
<tt class="docutils literal"><span class="pre">WSGIApplicationGroup</span></tt> directive, with <tt class="docutils literal"><span class="pre">WSGIProcessGroup</span></tt> dictating
what named group of processes a request is handled by, and
<tt class="docutils literal"><span class="pre">WSGIApplicationGroup</span></tt> dictating which named Python sub interpreter
context (application group) of those processes is used. In each distinct
process of a named group of processes, there will be a separate sub
interpreter instance of same name, for handling the requests accepted by
that process.</p>
<p>The argument to the <tt class="docutils literal"><span class="pre">WSGIApplicationGroup</span></tt> can be either one of four
special expanding variables or an explicit name of your own choosing.
The meaning of the special variables are:</p>
<p><strong>%{GLOBAL}</strong></p>
<blockquote>
<div><p>The application group name will be set to the empty string.</p>
<p>Any WSGI applications in the global application group will always be
executed within the context of the first interpreter created by Python
when it is initialised, of the process handling the request. Forcing a
WSGI application to run within the first interpreter can be necessary
when a third party C extension module for Python has used the
simplified threading API for manipulation of the Python GIL and thus
will not run correctly within any additional sub interpreters created
by Python.</p>
</div></blockquote>
<p><strong>%{SERVER}</strong></p>
<blockquote>
<div><p>The application group name will be set to the server hostname. If the
request arrived over a non standard HTTP/HTTPS port, the port number
will be added as a suffix to the group name separated by a colon.</p>
<p>For example, if the virtual host <tt class="docutils literal"><span class="pre">www.example.com</span></tt> is handling
requests on the standard HTTP port (80) and HTTPS port (443), a request
arriving on either port would see the application group name being set
to <tt class="docutils literal"><span class="pre">www.example.com</span></tt>. If instead the virtual host was handling requests
on port 8080, then the application group name would be set to
<tt class="docutils literal"><span class="pre">www.example.com:8080</span></tt>.</p>
</div></blockquote>
<p><strong>%{RESOURCE}</strong></p>
<blockquote>
<div><p>The application group name will be set to the server hostname and port
as for the <tt class="docutils literal"><span class="pre">%{SERVER}</span></tt> variable, to which the value of WSGI environment
variable <tt class="docutils literal"><span class="pre">SCRIPT_NAME</span></tt> is appended separated by the file separator
character.</p>
<p>For example, if the virtual host <tt class="docutils literal"><span class="pre">www.example.com</span></tt> was handling
requests on port 8080 and the URL-path which mapped to the WSGI
application was:</p>
<div class="highlight-python"><div class="highlight"><pre><span></span>http://www.example.com/wsgi-scripts/foo
</pre></div>
</div>
<p>then the application group name would be set to:</p>
<div class="highlight-python"><div class="highlight"><pre><span></span>www.example.com:8080|/wsgi-scripts/foo
</pre></div>
</div>
<p>The effect of using the <tt class="docutils literal"><span class="pre">%{RESOURCE}</span></tt> variable expansion is for each
application on any server to be isolated from all others by being
mapped to its own Python sub interpreter.</p>
</div></blockquote>
<p><strong>%{ENV:variable}</strong></p>
<blockquote>
<div>The application group name will be set to the value of the named
environment variable. The environment variable is looked-up via the
internal Apache notes and subprocess environment data structures and
(if not found there) via <tt class="docutils literal"><span class="pre">getenv()</span></tt> from the Apache server process.</div></blockquote>
<p>In an Apache configuration file, environment variables accessible using
the <tt class="docutils literal"><span class="pre">%{ENV}</span></tt> variable reference can be setup by using directives such as
<a class="reference external" href="http://httpd.apache.org/docs/2.2/mod/mod_env.html#setenv">SetEnv</a> and <a class="reference external" href="http://httpd.apache.org/docs/2.2/mod/mod_rewrite.html#rewriterule">RewriteRule</a>.</p>
<p>For example, to group all WSGI scripts for a specific user when using
<a class="reference external" href="http://httpd.apache.org/docs/2.2/mod/mod_userdir.html">mod_userdir</a> within the same application group, the following could be
used:</p>
<div class="highlight-python"><div class="highlight"><pre><span></span>RewriteEngine On
RewriteCond %{REQUEST_URI} ^/~([^/]+)
RewriteRule . - [E=APPLICATION_GROUP:~%1]

&lt;Directory /home/*/public_html/wsgi-scripts/&gt;
Options ExecCGI
SetHandler wsgi-script
WSGIApplicationGroup %{ENV:APPLICATION_GROUP}
&lt;/Directory&gt;
</pre></div>
</div>
<p>Note that in embedded mode or a multi process daemon process group, there
will be an instance of the named sub interpreter in each process. Thus the
directive only ensures that request is handled in the named sub interpreter
within the process that handles the request. If you need to ensure that
requests for a specific user always go back to the exact same sub interpreter,
then you will need to use a daemon process group with only a single process,
or implement sticky session mechanism across a number of single process
daemon process groups.</p>
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