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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-05-07 02:04:06 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-05-07 02:04:06 +0000
commit5dff2d61cc1c27747ee398e04d8e02843aabb1f8 (patch)
treea67c336b406c8227bac912beb74a1ad3cdc55100 /docs/manual/developer/modules.html.en
parentInitial commit. (diff)
downloadapache2-5dff2d61cc1c27747ee398e04d8e02843aabb1f8.tar.xz
apache2-5dff2d61cc1c27747ee398e04d8e02843aabb1f8.zip
Adding upstream version 2.4.38.upstream/2.4.38upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
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+<?xml version="1.0" encoding="ISO-8859-1"?>
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+<title>Converting Modules from Apache 1.3 to Apache 2.0 - Apache HTTP Server Version 2.4</title>
+<link href="../style/css/manual.css" rel="stylesheet" media="all" type="text/css" title="Main stylesheet" />
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+<body id="manual-page"><div id="page-header">
+<p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/directives.html">Directives</a> | <a href="http://wiki.apache.org/httpd/FAQ">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p>
+<p class="apache">Apache HTTP Server Version 2.4</p>
+<img alt="" src="../images/feather.png" /></div>
+<div class="up"><a href="./"><img title="&lt;-" alt="&lt;-" src="../images/left.gif" /></a></div>
+<div id="path">
+<a href="http://www.apache.org/">Apache</a> &gt; <a href="http://httpd.apache.org/">HTTP Server</a> &gt; <a href="http://httpd.apache.org/docs/">Documentation</a> &gt; <a href="../">Version 2.4</a> &gt; <a href="./">Developer Documentation</a></div><div id="page-content"><div id="preamble"><h1>Converting Modules from Apache 1.3 to Apache 2.0</h1>
+<div class="toplang">
+<p><span>Available Languages: </span><a href="../en/developer/modules.html" title="English">&nbsp;en&nbsp;</a> |
+<a href="../ja/developer/modules.html" hreflang="ja" rel="alternate" title="Japanese">&nbsp;ja&nbsp;</a></p>
+</div>
+
+ <p>This is a first attempt at writing the lessons I learned
+ when trying to convert the <code>mod_mmap_static</code> module to Apache
+ 2.0. It's by no means definitive and probably won't even be
+ correct in some ways, but it's a start.</p>
+</div>
+<div id="quickview"><a href="https://www.apache.org/foundation/contributing.html" class="badge"><img src="https://www.apache.org/images/SupportApache-small.png" alt="Support Apache!" /></a><ul id="toc"><li><img alt="" src="../images/down.gif" /> <a href="#easy">The easier changes ...</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#messy">The messier changes...</a></li>
+</ul><h3>See also</h3><ul class="seealso"><li><a href="#comments_section">Comments</a></li></ul></div>
+<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="section">
+<h2><a name="easy" id="easy">The easier changes ...</a></h2>
+
+ <h3><a name="cleanup" id="cleanup">Cleanup Routines</a></h3>
+ <p>These now need to be of type <code>apr_status_t</code> and return a
+ value of that type. Normally the return value will be
+ <code>APR_SUCCESS</code> unless there is some need to signal an error in
+ the cleanup. Be aware that even though you signal an error not all code
+ yet checks and acts upon the error.</p>
+
+
+ <h3><a name="init" id="init">Initialisation Routines</a></h3>
+ <p>These should now be renamed to better signify where they sit
+ in the overall process. So the name gets a small change from
+ <code>mmap_init</code> to <code>mmap_post_config</code>. The arguments
+ passed have undergone a radical change and now look like</p>
+
+ <ul>
+ <li><code>apr_pool_t *p</code></li>
+ <li><code>apr_pool_t *plog</code></li>
+ <li><code>apr_pool_t *ptemp</code></li>
+ <li><code>server_rec *s</code></li>
+ </ul>
+
+
+ <h3><a name="datatypes" id="datatypes">Data Types</a></h3>
+ <p>A lot of the data types have been moved into the <a href="http://apr.apache.org/">APR</a>. This means that some have had
+ a name change, such as the one shown above. The following is a brief
+ list of some of the changes that you are likely to have to make.</p>
+
+ <ul>
+ <li><code>pool</code> becomes <code>apr_pool_t</code></li>
+ <li><code>table</code> becomes <code>apr_table_t</code></li>
+ </ul>
+
+</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
+<div class="section">
+<h2><a name="messy" id="messy">The messier changes...</a></h2>
+
+ <h3><a name="register-hooks" id="register-hooks">Register Hooks</a></h3>
+ <p>The new architecture uses a series of hooks to provide for
+ calling your functions. These you'll need to add to your module
+ by way of a new function, <code>static void register_hooks(void)</code>.
+ The function is really reasonably straightforward once you
+ understand what needs to be done. Each function that needs
+ calling at some stage in the processing of a request needs to
+ be registered, handlers do not. There are a number of phases
+ where functions can be added, and for each you can specify with
+ a high degree of control the relative order that the function
+ will be called in.</p>
+
+ <p>This is the code that was added to <code>mod_mmap_static</code>:</p>
+ <div class="example"><pre>static void register_hooks(void)
+{
+ static const char * const aszPre[]={ "http_core.c",NULL };
+ ap_hook_post_config(mmap_post_config,NULL,NULL,HOOK_MIDDLE);
+ ap_hook_translate_name(mmap_static_xlat,aszPre,NULL,HOOK_LAST);
+};</pre></div>
+
+ <p>This registers 2 functions that need to be called, one in
+ the <code>post_config</code> stage (virtually every module will need this
+ one) and one for the <code>translate_name</code> phase. note that while
+ there are different function names the format of each is
+ identical. So what is the format?</p>
+
+ <div class="example"><p><code>
+ ap_hook_<var>phase_name</var>(<var>function_name</var>,
+ <var>predecessors</var>, <var>successors</var>, <var>position</var>);
+ </code></p></div>
+
+ <p>There are 3 hook positions defined...</p>
+
+ <ul>
+ <li><code>HOOK_FIRST</code></li>
+ <li><code>HOOK_MIDDLE</code></li>
+ <li><code>HOOK_LAST</code></li>
+ </ul>
+
+ <p>To define the position you use the position and then modify
+ it with the predecessors and successors. Each of the modifiers
+ can be a list of functions that should be called, either before
+ the function is run (predecessors) or after the function has
+ run (successors).</p>
+
+ <p>In the <code>mod_mmap_static</code> case I didn't care about the
+ <code>post_config</code> stage, but the <code>mmap_static_xlat</code>
+ <strong>must</strong> be called after the core module had done its name
+ translation, hence the use of the aszPre to define a modifier to the
+ position <code>HOOK_LAST</code>.</p>
+
+
+ <h3><a name="moddef" id="moddef">Module Definition</a></h3>
+ <p>There are now a lot fewer stages to worry about when
+ creating your module definition. The old definition looked
+ like</p>
+
+ <div class="example"><pre>module MODULE_VAR_EXPORT <var>module_name</var>_module =
+{
+ STANDARD_MODULE_STUFF,
+ /* initializer */
+ /* dir config creater */
+ /* dir merger --- default is to override */
+ /* server config */
+ /* merge server config */
+ /* command handlers */
+ /* handlers */
+ /* filename translation */
+ /* check_user_id */
+ /* check auth */
+ /* check access */
+ /* type_checker */
+ /* fixups */
+ /* logger */
+ /* header parser */
+ /* child_init */
+ /* child_exit */
+ /* post read-request */
+};</pre></div>
+
+ <p>The new structure is a great deal simpler...</p>
+ <div class="example"><pre>module MODULE_VAR_EXPORT <var>module_name</var>_module =
+{
+ STANDARD20_MODULE_STUFF,
+ /* create per-directory config structures */
+ /* merge per-directory config structures */
+ /* create per-server config structures */
+ /* merge per-server config structures */
+ /* command handlers */
+ /* handlers */
+ /* register hooks */
+};</pre></div>
+
+ <p>Some of these read directly across, some don't. I'll try to
+ summarise what should be done below.</p>
+
+ <p>The stages that read directly across :</p>
+
+ <dl>
+ <dt><code>/* dir config creater */</code></dt>
+ <dd><code>/* create per-directory config structures */</code></dd>
+
+ <dt><code>/* server config */</code></dt>
+ <dd><code>/* create per-server config structures */</code></dd>
+
+ <dt><code>/* dir merger */</code></dt>
+ <dd><code>/* merge per-directory config structures */</code></dd>
+
+ <dt><code>/* merge server config */</code></dt>
+ <dd><code>/* merge per-server config structures */</code></dd>
+
+ <dt><code>/* command table */</code></dt>
+ <dd><code>/* command apr_table_t */</code></dd>
+
+ <dt><code>/* handlers */</code></dt>
+ <dd><code>/* handlers */</code></dd>
+ </dl>
+
+ <p>The remainder of the old functions should be registered as
+ hooks. There are the following hook stages defined so
+ far...</p>
+
+ <dl>
+ <dt><code>ap_hook_pre_config</code></dt>
+ <dd>do any setup required prior to processing configuration
+ directives</dd>
+
+ <dt><code>ap_hook_check_config</code></dt>
+ <dd>review configuration directive interdependencies</dd>
+
+ <dt><code>ap_hook_test_config</code></dt>
+ <dd>executes only with <code>-t</code> option</dd>
+
+ <dt><code>ap_hook_open_logs</code></dt>
+ <dd>open any specified logs</dd>
+
+ <dt><code>ap_hook_post_config</code></dt>
+ <dd>this is where the old <code>_init</code> routines get
+ registered</dd>
+
+ <dt><code>ap_hook_http_method</code></dt>
+ <dd>retrieve the http method from a request. (legacy)</dd>
+
+ <dt><code>ap_hook_auth_checker</code></dt>
+ <dd>check if the resource requires authorization</dd>
+
+ <dt><code>ap_hook_access_checker</code></dt>
+ <dd>check for module-specific restrictions</dd>
+
+ <dt><code>ap_hook_check_user_id</code></dt>
+ <dd>check the user-id and password</dd>
+
+ <dt><code>ap_hook_default_port</code></dt>
+ <dd>retrieve the default port for the server</dd>
+
+ <dt><code>ap_hook_pre_connection</code></dt>
+ <dd>do any setup required just before processing, but after
+ accepting</dd>
+
+ <dt><code>ap_hook_process_connection</code></dt>
+ <dd>run the correct protocol</dd>
+
+ <dt><code>ap_hook_child_init</code></dt>
+ <dd>call as soon as the child is started</dd>
+
+ <dt><code>ap_hook_create_request</code></dt>
+ <dd>??</dd>
+
+ <dt><code>ap_hook_fixups</code></dt>
+ <dd>last chance to modify things before generating content</dd>
+
+ <dt><code>ap_hook_handler</code></dt>
+ <dd>generate the content</dd>
+
+ <dt><code>ap_hook_header_parser</code></dt>
+ <dd>lets modules look at the headers, not used by most modules, because
+ they use <code>post_read_request</code> for this</dd>
+
+ <dt><code>ap_hook_insert_filter</code></dt>
+ <dd>to insert filters into the filter chain</dd>
+
+ <dt><code>ap_hook_log_transaction</code></dt>
+ <dd>log information about the request</dd>
+
+ <dt><code>ap_hook_optional_fn_retrieve</code></dt>
+ <dd>retrieve any functions registered as optional</dd>
+
+ <dt><code>ap_hook_post_read_request</code></dt>
+ <dd>called after reading the request, before any other phase</dd>
+
+ <dt><code>ap_hook_quick_handler</code></dt>
+ <dd>called before any request processing, used by cache modules.</dd>
+
+ <dt><code>ap_hook_translate_name</code></dt>
+ <dd>translate the URI into a filename</dd>
+
+ <dt><code>ap_hook_type_checker</code></dt>
+ <dd>determine and/or set the doc type</dd>
+ </dl>
+
+</div></div>
+<div class="bottomlang">
+<p><span>Available Languages: </span><a href="../en/developer/modules.html" title="English">&nbsp;en&nbsp;</a> |
+<a href="../ja/developer/modules.html" hreflang="ja" rel="alternate" title="Japanese">&nbsp;ja&nbsp;</a></p>
+</div><div class="top"><a href="#page-header"><img src="../images/up.gif" alt="top" /></a></div><div class="section"><h2><a id="comments_section" name="comments_section">Comments</a></h2><div class="warning"><strong>Notice:</strong><br />This is not a Q&amp;A section. Comments placed here should be pointed towards suggestions on improving the documentation or server, and may be removed again by our moderators if they are either implemented or considered invalid/off-topic. Questions on how to manage the Apache HTTP Server should be directed at either our IRC channel, #httpd, on Freenode, or sent to our <a href="http://httpd.apache.org/lists.html">mailing lists</a>.</div>
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