93 lines
4.2 KiB
HTML
93 lines
4.2 KiB
HTML
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<!-- NOTE: This HTML is displayed inside the CHM file - hence some hrefs
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<HTML>
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<BODY>
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<TITLE>Introduction to Python ISAPI support</TITLE>
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<h2>Introduction to Python ISAPI support</h2>
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<h3>See also</h3>
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<ul>
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<li><a href="/isapi_modules.html">The isapi related modules</a>
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</li>
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<li><a href="/isapi_objects.html">The isapi related objects</a>
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</li>
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</ul>
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<p><i>Note: if you are viewing this documentation directly from disk,
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most links in this document will fail - you can also find this document in the
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CHM file that comes with pywin32, where the links will work</i>
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<h3>Introduction</h3>
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This documents Python support for hosting ISAPI exensions and filters inside
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Microsoft Internet Information Server (IIS). It assumes a basic understanding
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of the ISAPI filter and extension mechanism.
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<p>
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In summary, to implement a filter or extension, you provide a Python module
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which defines a Filter and/or Extension class. Once your class has been
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loaded, IIS/ISAPI will, via an extension DLL, call methods on your class.
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<p>
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A filter and a class instance need only provide 3 methods - for filters they
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are called <code>GetFilterVersion</code>, <code>HttpFilterProc</code> and
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<code>TerminateFilter</code>. For extensions they
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are named <code>GetExtensionVersion</code>, <code>HttpExtensionProc</code> and
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<code>TerminateExtension</code>. If you are familiar with writing ISAPI
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extensions in C/C++, these names and their purpose will be familiar.
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<p>
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Most of the work is done in the <code>HttpFilterProc</code> and
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<code>HttpExtensionProc</code> methods. These both take a single
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parameter - an <a href="/HTTP_FILTER_CONTEXT.html">HTTP_FILTER_CONTEXT</a> and
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<a href="/EXTENSION_CONTROL_BLOCK.html">EXTENSION_CONTROL_BLOCK</a>
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object respectively.
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<p>
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In addition to these components, there is an 'isapi' package, containing
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support facilities (base-classes, exceptions, etc) which can be leveraged
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by the extension.
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<h4>Base classes</h4>
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There are a number of base classes provided to make writing extensions a little
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simpler. Of particular note is <code>isapi.threaded_extension.ThreadPoolExtension</code>.
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This implements a thread-pool and informs IIS that the request is progressing
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in the background. Your sub-class need only provide a <code>Dispatch</code>
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method, which is called on one of the worker threads rather than the thread
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that the request came in on.
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<p>
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There is base-class for a filter in <code>isapi.simple</code>, but there is no
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equivilent threaded filter - filters work under a different model, where
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background processing is not possible.
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<h4>Samples</h4>
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Please see the <code>isapi/samples</code> directory for some sample filters
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and extensions.
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<H3>Implementation</H3>
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A Python ISAPI filter extension consists of 2 main components:
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<UL>
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<LI>A DLL used by ISAPI to interface with Python.</LI>
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<LI>A Python script used by that DLL to implement the filter or extension
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functionality</LI>
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</UL>
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<h4>Extension DLL</h4>
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The DLL is usually managed automatically by the isapi.install module. As the
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Python script for the extension is installed, a generic DLL provided with
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the isapi package is installed next to the script, and IIS configured to
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use this DLL.
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<p>
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The name of the DLL always has the same base name as the Python script, but
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with a leading underscore (_), and an extension of .dll. For example, the
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sample "redirector.py" will, when installed, have "_redirector.dll" created
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in the same directory.
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<p/>
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The Python script may provide 2 entry points - methods named __FilterFactory__
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and __ExtensionFactory__, both taking no arguments and returning a filter or
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extension object.
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<h3>Using py2exe and the isapi package</h3>
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You can instruct py2exe to create a 'frozen' Python ISAPI filter/extension.
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In this case, py2exe will create a package with everything you need in one
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directory, and the Python source file embedded in the .zip file.
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<p>
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In general, you will want to build a seperate installation executable along
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with the ISAPI extension. This executable will be built from the same script.
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See the ISAPI sample in the py2exe distribution.
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