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<title>mod_log_debug - Apache HTTP Server</title>
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<div id="preamble"><h1>Apache Module mod_log_debug</h1>
<div class="toplang">
<p><span>Available Languages: </span><a href="../en/mod/mod_log_debug.html" title="English">&nbsp;en&nbsp;</a> |
<a href="../fr/mod/mod_log_debug.html" hreflang="fr" rel="alternate" title="Français">&nbsp;fr&nbsp;</a></p>
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<table class="module"><tr><th><a href="module-dict.html#Description">Description:</a></th><td>Additional configurable debug logging</td></tr>
<tr><th><a href="module-dict.html#Status">Status:</a></th><td>Experimental</td></tr>
<tr><th><a href="module-dict.html#ModuleIdentifier">Module Identifier:</a></th><td>log_debug_module</td></tr>
<tr><th><a href="module-dict.html#SourceFile">Source File:</a></th><td>mod_log_debug.c</td></tr>
<tr><th><a href="module-dict.html#Compatibility">Compatibility:</a></th><td>Available in Apache 2.3.14 and later</td></tr></table>
</div>
<div id="quickview"><h3 class="directives">Directives</h3>
<ul id="toc">
<li><img alt="" src="../images/down.gif" /> <a href="#logmessage">LogMessage</a></li>
</ul>
<h3>Topics</h3>
<ul id="topics">
<li><img alt="" src="../images/down.gif" /> <a href="#examples">Examples</a></li>
</ul><ul class="seealso"><li><a href="#comments_section">Comments</a></li></ul></div>
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<h2><a name="examples" id="examples">Examples</a></h2>

    <ol>
      <li>
        Log message after request to /foo/* is processed:

        <pre class="prettyprint lang-config">
&lt;Location /foo/&gt;
&nbsp;&nbsp;LogMessage "/foo/ has been requested"
&lt;/Location&gt;
        </pre>

      </li>

      <li>
        Log message if request to /foo/* is processed in a sub-request:
        <pre class="prettyprint lang-config">
&lt;Location /foo/&gt;
&nbsp;&nbsp;LogMessage "subrequest to /foo/" hook=type_checker expr=%{IS_SUBREQ}
&lt;/Location&gt;
        </pre>


        The default log_transaction hook is not executed for sub-requests,
        therefore we have to use a different hook.
      </li>


      <li>
        Log message if an IPv6 client causes a request timeout:
        <pre class="prettyprint lang-config">
            LogMessage "IPv6 timeout from %{REMOTE_ADDR}" "expr=-T %{IPV6} &amp;&amp; %{REQUEST_STATUS} = 408"
        </pre>

        Note the placing of the double quotes for the <code>expr=</code> argument.
      </li>

      <li>
        Log the value of the "X-Foo" request environment variable in each
        stage of the request:
        <pre class="prettyprint lang-config">
&lt;Location /&gt;
&nbsp;&nbsp;LogMessage "%{reqenv:X-Foo}" hook=all
&lt;/Location&gt;
        </pre>

        Together with microsecond time stamps in the error log,
        <code>hook=all</code> also lets you determine the times spent
        in the different parts of the request processing.
      </li>

    </ol>
</div>
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<div class="directive-section"><h2><a name="LogMessage" id="LogMessage">LogMessage</a> <a name="logmessage" id="logmessage">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Log user-defined message to error log
</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>LogMessage <var>message</var>
[hook=<var>hook</var>] [expr=<var>expression</var>]
</code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>Unset</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>directory</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Experimental</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_log_debug</td></tr>
</table>
    <p>This directive causes a user defined message to be logged to the
    error log. The message can use variables and functions from the
    <a href="../expr.html">ap_expr syntax</a>. References to HTTP headers
    will not cause header names to be added to the Vary header. The
    messages are logged at loglevel info.</p>

    <p>The hook specifies before which phase of request processing the message
    will be logged. The following hooks are supported:</p>

    <table class="bordered"><tr class="header"><th>Name</th></tr>
<tr><td><code>translate_name</code></td></tr>
<tr class="odd"><td><code>type_checker</code></td></tr>
<tr><td><code>quick_handler</code></td></tr>
<tr class="odd"><td><code>map_to_storage</code></td></tr>
<tr><td><code>check_access</code></td></tr>
<tr class="odd"><td><code>check_access_ex</code></td></tr>
<tr><td><code>insert_filter</code></td></tr>
<tr class="odd"><td><code>check_authn</code></td></tr>
<tr><td><code>check_authz</code></td></tr>
<tr class="odd"><td><code>fixups</code></td></tr>
<tr><td><code>handler</code></td></tr>
<tr class="odd"><td><code>log_transaction</code></td></tr>
</table>

    <p>The default is <code>log_transaction</code>. The special value
    <code>all</code> is also supported, causing a message to be logged at each
    phase. Not all hooks are executed for every request.</p>

    <p>The optional expression allows to restrict the message if a
    condition is met. The details of the expression syntax are described in
    the <a href="../expr.html">ap_expr documentation</a>. References to HTTP
    headers will not cause the header names to be added to the Vary header.</p>


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