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author | Luca Toscano <elukey@apache.org> | 2016-02-19 08:05:22 +0000 |
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committer | Luca Toscano <elukey@apache.org> | 2016-02-19 08:05:22 +0000 |
commit | 489f54581f0cdb56b2be4fba5f0b0569dc079062 (patch) | |
tree | ffac99bd69e512cda5b9af4d6de411fc1af245f5 /docs/manual/sections.html.en | |
parent | 89f3342eebd788e8ff53e3bf4074fbfbbce4f8f7 (diff) | |
download | httpd-489f54581f0cdb56b2be4fba5f0b0569dc079062.tar.gz |
Documentation rebuild
git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1731195 13f79535-47bb-0310-9956-ffa450edef68
Diffstat (limited to 'docs/manual/sections.html.en')
-rw-r--r-- | docs/manual/sections.html.en | 63 |
1 files changed, 49 insertions, 14 deletions
diff --git a/docs/manual/sections.html.en b/docs/manual/sections.html.en index 5e115c518e..33ce214887 100644 --- a/docs/manual/sections.html.en +++ b/docs/manual/sections.html.en @@ -361,12 +361,12 @@ see the <a href="vhosts/">Virtual Host Documentation</a>.</p> and <code class="directive"><a href="./mod/mod_proxy.html#proxymatch"><ProxyMatch></a></code> containers apply enclosed configuration directives only to sites accessed through <code class="module"><a href="./mod/mod_proxy.html">mod_proxy</a></code>'s proxy server -that match the specified URL. For example, the following configuration -will prevent the proxy server from being used to access the -<code>www.example.com</code> website.</p> +that match the specified URL. For example, the following configuration +will allow only a subset of clients to access the +<code>www.example.com</code> website using the proxy server:</p> <pre class="prettyprint lang-config"><Proxy "http://www.example.com/*"> - Require all granted + Require host yournetwork.example.com </Proxy></pre> </div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div> @@ -452,14 +452,7 @@ are interpreted, it is important to understand how this works.</p> container takes the place of the <code class="directive"><a href="./mod/core.html#directory"><Directory></a></code> container in the processing order.</p> - <p>Later sections override earlier ones, however each module is responsible - for interpreting what form this override takes. A later configuration section - with directives from a given module might cause a conceptual "merge" of some - directives, all directives, or a complete replacement of the modules - configuration with the module defaults and directives explicitly listed in - the later context.</p> - -<div class="note"><h3>Technical Note</h3> + <div class="note"><h3>Technical Note</h3> There is actually a <code><Location></code>/<code><LocationMatch></code> sequence performed just before the name translation phase @@ -467,9 +460,50 @@ are interpreted, it is important to understand how this works.</p> are used to map URLs to filenames). The results of this sequence are completely thrown away after the translation has completed. -</div> + </div> + +<h3><a name="relationship-module-configuration" id="relationship-module-configuration">Relationship between modules and configuration sections</a></h3> + <p>One question that often arises after reading how configuration sections are + merged is related to how and when directives of specific modules like <code class="module"><a href="./mod/mod_rewrite.html">mod_rewrite</a></code> + are processed. The answer is not trivial and needs a bit of background. + Each httpd module manages its own configuration, and each of its directives in httpd.conf specify one piece + of configuration in a particular context. httpd does not execute a command as it is read.</p> + <p>At runtime, the core of httpd iterates over the defined configuration sections in the order + described above to determine which ones apply to the current request. When the first section matches, + it is considered the current configuration for this request. If a subsequent section matches too, + then each module with a directive in either of the sections is given a chance to merge its configuration between the two sections. The result is a third configuration, and the process goes on until all the configuration sections + are evaluated.</p> + <p>After the above step, the "real" processing of the HTTP request begins: each module has a chance to run + and perform whatever tasks they like. They can retrieve their own final merged configuration from the core + of the httpd to determine how they should act.</p> + <p>An example can help to visualize the whole process. The following configuration uses the + <code class="directive"><a href="./mod/mod_headers.html#header">Header</a></code> directive of <code class="module"><a href="./mod/mod_headers.html">mod_headers</a></code> to set + a specific HTTP header. What value will httpd set in the <code>CustomHeaderName</code> header for a request to + <code>/example/index.html</code> ? + </p> + <pre class="prettyprint lang-config"><Directory "/"> + Header set CustomHeaderName one + <FilesMatch ".*"> + Header set CustomHeaderName three + </FilesMatch> +</Directory> -<h3><a name="merge-examples" id="merge-examples">Some Examples</a></h3> +<Directory "/example"> + Header set CustomHeaderName two +</Directory></pre> + + <ul> + <li><code class="directive">Directory</code> "/" matches and an initial configuration to set the <code>CustomHeaderName</code> header with the value <code>one</code> is created.</li> + <li><code class="directive">Directory</code> "/example" matches, and since <code class="module"><a href="./mod/mod_headers.html">mod_headers</a></code> specifies in its code to override in case of a merge, a new configuration is created to set the <code>CustomHeaderName</code> header with the value <code>two</code>.</li> + <li><code class="directive">FilesMatch</code> ".*" matches and another merge opportunity arises, causing the <code>CustomHeaderName</code> header to be set with the value <code>three</code>.</li> + <li>Eventually during the next steps of the HTTP request processing <code class="module"><a href="./mod/mod_headers.html">mod_headers</a></code> will be called and it will receive the configuration to set the <code>CustomHeaderName</code> header with the value <code>three</code>. <code class="module"><a href="./mod/mod_headers.html">mod_headers</a></code> normally uses this configuration to perfom its job, namely setting the foo header. This does not mean that a module can't perform a more complex action like discarding directives because not needed or deprecated, etc..</li> + </ul> + + <p>This is true for .htaccess too since they have the same priority as <code class="directive">Directory</code> in the merge order. The important concept to understand is that configuration sections like <code class="directive">Directory</code> and <code class="directive">FilesMatch</code> are not comparable to module specific directives like <code class="directive"><a href="./mod/mod_headers.html#header">Header</a></code> or <code class="directive"><a href="./mod/mod_rewrite.html#rewriterule">RewriteRule</a></code> because they operate on different levels. + </p> + + +<h3><a name="merge-examples" id="merge-examples">Some useful examples</a></h3> <p>Below is an artificial example to show the order of merging. Assuming they all apply to the request, the directives in @@ -499,6 +533,7 @@ E.</p> </Directory></pre> + <p>For a more concrete example, consider the following. Regardless of any access restrictions placed in <code class="directive"><a href="./mod/core.html#directory"><Directory></a></code> sections, the <code class="directive"><a href="./mod/core.html#location"><Location></a></code> section will be evaluated last and will allow unrestricted access to the server. In |