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<title>Converting Modules from Apache 1.3 to Apache 2.0 - Apache HTTP Server</title>
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<p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/directives.html">Directives</a> | <a href="../faq/">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p>
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<p class="apache">Apache HTTP Server Version 2.2</p>
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<img alt="" src="../images/feather.gif" /></div>
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<div class="up"><a href="./"><img title="<-" alt="<-" src="../images/left.gif" /></a></div>
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<a href="http://www.apache.org/">Apache</a> > <a href="http://httpd.apache.org/">HTTP Server</a> > <a href="http://httpd.apache.org/docs/">Documentation</a> > <a href="../">Version 2.2</a> > <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>
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<p><span>Available Languages: </span><a href="../en/developer/modules.html" title="English"> en </a> |
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<a href="../ja/developer/modules.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a></p>
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<p>This is a first attempt at writing the lessons I learned
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when trying to convert the <code>mod_mmap_static</code> module to Apache
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2.0. It's by no means definitive and probably won't even be
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correct in some ways, but it's a start.</p>
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<div id="quickview"><ul id="toc"><li><img alt="" src="../images/down.gif" /> <a href="#easy">The easier changes ...</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#messy">The messier changes...</a></li>
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<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
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<h2><a name="easy" id="easy">The easier changes ...</a></h2>
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<h3><a name="cleanup" id="cleanup">Cleanup Routines</a></h3>
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<p>These now need to be of type <code>apr_status_t</code> and return a
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value of that type. Normally the return value will be
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<code>APR_SUCCESS</code> unless there is some need to signal an error in
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the cleanup. Be aware that even though you signal an error not all code
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yet checks and acts upon the error.</p>
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<h3><a name="init" id="init">Initialisation Routines</a></h3>
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<p>These should now be renamed to better signify where they sit
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in the overall process. So the name gets a small change from
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<code>mmap_init</code> to <code>mmap_post_config</code>. The arguments
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passed have undergone a radical change and now look like</p>
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<li><code>apr_pool_t *p</code></li>
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<li><code>apr_pool_t *plog</code></li>
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<li><code>apr_pool_t *ptemp</code></li>
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<li><code>server_rec *s</code></li>
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<h3><a name="datatypes" id="datatypes">Data Types</a></h3>
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<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
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a name change, such as the one shown above. The following is a brief
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list of some of the changes that you are likely to have to make.</p>
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<li><code>pool</code> becomes <code>apr_pool_t</code></li>
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<li><code>table</code> becomes <code>apr_table_t</code></li>
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</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
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<h2><a name="messy" id="messy">The messier changes...</a></h2>
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<h3><a name="register-hooks" id="register-hooks">Register Hooks</a></h3>
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<p>The new architecture uses a series of hooks to provide for
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calling your functions. These you'll need to add to your module
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by way of a new function, <code>static void register_hooks(void)</code>.
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The function is really reasonably straightforward once you
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understand what needs to be done. Each function that needs
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calling at some stage in the processing of a request needs to
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be registered, handlers do not. There are a number of phases
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where functions can be added, and for each you can specify with
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a high degree of control the relative order that the function
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will be called in.</p>
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<p>This is the code that was added to <code>mod_mmap_static</code>:</p>
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<div class="example"><pre>
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static void register_hooks(void)
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static const char * const aszPre[]={ "http_core.c",NULL };
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ap_hook_post_config(mmap_post_config,NULL,NULL,HOOK_MIDDLE);
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ap_hook_translate_name(mmap_static_xlat,aszPre,NULL,HOOK_LAST);
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<p>This registers 2 functions that need to be called, one in
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the <code>post_config</code> stage (virtually every module will need this
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one) and one for the <code>translate_name</code> phase. note that while
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there are different function names the format of each is
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identical. So what is the format?</p>
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<div class="example"><p><code>
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ap_hook_<var>phase_name</var>(<var>function_name</var>,
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<var>predecessors</var>, <var>successors</var>, <var>position</var>);
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<p>There are 3 hook positions defined...</p>
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<li><code>HOOK_FIRST</code></li>
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<li><code>HOOK_MIDDLE</code></li>
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<li><code>HOOK_LAST</code></li>
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<p>To define the position you use the position and then modify
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it with the predecessors and successors. Each of the modifiers
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can be a list of functions that should be called, either before
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the function is run (predecessors) or after the function has
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run (successors).</p>
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<p>In the <code>mod_mmap_static</code> case I didn't care about the
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<code>post_config</code> stage, but the <code>mmap_static_xlat</code>
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<strong>must</strong> be called after the core module had done it's name
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translation, hence the use of the aszPre to define a modifier to the
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position <code>HOOK_LAST</code>.</p>
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<h3><a name="moddef" id="moddef">Module Definition</a></h3>
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<p>There are now a lot fewer stages to worry about when
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creating your module definition. The old defintion looked
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<div class="example"><pre>
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module MODULE_VAR_EXPORT <var>module_name</var>_module =
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STANDARD_MODULE_STUFF,
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/* dir config creater */
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/* dir merger --- default is to override */
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/* merge server config */
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/* command handlers */
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/* filename translation */
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/* post read-request */
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<p>The new structure is a great deal simpler...</p>
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<div class="example"><pre>
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module MODULE_VAR_EXPORT <var>module_name</var>_module =
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STANDARD20_MODULE_STUFF,
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/* create per-directory config structures */
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/* merge per-directory config structures */
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/* create per-server config structures */
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/* merge per-server config structures */
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/* command handlers */
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<p>Some of these read directly across, some don't. I'll try to
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summarise what should be done below.</p>
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<p>The stages that read directly across :</p>
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<dt><code>/* dir config creater */</code></dt>
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<dd><code>/* create per-directory config structures */</code></dd>
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<dt><code>/* server config */</code></dt>
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<dd><code>/* create per-server config structures */</code></dd>
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<dt><code>/* dir merger */</code></dt>
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<dd><code>/* merge per-directory config structures */</code></dd>
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<dt><code>/* merge server config */</code></dt>
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<dd><code>/* merge per-server config structures */</code></dd>
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<dt><code>/* command table */</code></dt>
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<dd><code>/* command apr_table_t */</code></dd>
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<dt><code>/* handlers */</code></dt>
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<dd><code>/* handlers */</code></dd>
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<p>The remainder of the old functions should be registered as
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hooks. There are the following hook stages defined so
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<dt><code>ap_hook_post_config</code></dt>
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<dd>this is where the old <code>_init</code> routines get
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<dt><code>ap_hook_http_method</code></dt>
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<dd>retrieve the http method from a request. (legacy)</dd>
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<dt><code>ap_hook_open_logs</code></dt>
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<dd>open any specified logs</dd>
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<dt><code>ap_hook_auth_checker</code></dt>
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<dd>check if the resource requires authorization</dd>
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<dt><code>ap_hook_access_checker</code></dt>
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<dd>check for module-specific restrictions</dd>
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<dt><code>ap_hook_check_user_id</code></dt>
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<dd>check the user-id and password</dd>
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<dt><code>ap_hook_default_port</code></dt>
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<dd>retrieve the default port for the server</dd>
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<dt><code>ap_hook_pre_connection</code></dt>
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<dd>do any setup required just before processing, but after
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<dt><code>ap_hook_process_connection</code></dt>
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<dd>run the correct protocol</dd>
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<dt><code>ap_hook_child_init</code></dt>
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<dd>call as soon as the child is started</dd>
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<dt><code>ap_hook_create_request</code></dt>
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<dt><code>ap_hook_fixups</code></dt>
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<dd>last chance to modify things before generating content</dd>
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<dt><code>ap_hook_handler</code></dt>
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<dd>generate the content</dd>
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<dt><code>ap_hook_header_parser</code></dt>
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<dd>lets modules look at the headers, not used by most modules, because
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they use <code>post_read_request</code> for this</dd>
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<dt><code>ap_hook_insert_filter</code></dt>
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<dd>to insert filters into the filter chain</dd>
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<dt><code>ap_hook_log_transaction</code></dt>
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<dd>log information about the request</dd>
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<dt><code>ap_hook_optional_fn_retrieve</code></dt>
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<dd>retrieve any functions registered as optional</dd>
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<dt><code>ap_hook_post_read_request</code></dt>
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<dd>called after reading the request, before any other phase</dd>
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<dt><code>ap_hook_quick_handler</code></dt>
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<dd>called before any request processing, used by cache modules.</dd>
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<dt><code>ap_hook_translate_name</code></dt>
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<dd>translate the URI into a filename</dd>
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<dt><code>ap_hook_type_checker</code></dt>
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<dd>determine and/or set the doc type</dd>
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<p><span>Available Languages: </span><a href="../en/developer/modules.html" title="English"> en </a> |
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<p class="apache">Copyright 2006 The Apache Software Foundation.<br />Licensed under the <a href="http://www.apache.org/licenses/LICENSE-2.0">Apache License, Version 2.0</a>.</p>
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