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<?xml-stylesheet type="text/xsl" href="/style/manual.en.xsl"?>

<modulesynopsis metafile="mod_log_debug.xml.meta">

<name>mod_log_debug</name>

<description>Additional configurable debug logging</description>

<status>Experimental</status>

<sourcefile>mod_log_debug.c</sourcefile>

<identifier>log_debug_module</identifier>

<compatibility>Available in Apache 2.3.14 and later</compatibility>

<section id="examples"><title>Examples</title>

<ol>

<li>

Log message after request to /foo/* is processed:

<highlight language="config">

&lt;Location "/foo/"&gt;

&nbsp;&nbsp;LogMessage "/foo/ has been requested"

&lt;/Location&gt;

</highlight>

</li>

<li>

Log message if request to /foo/* is processed in a sub-request:

<highlight language="config">

&lt;Location "/foo/"&gt;

&nbsp;&nbsp;LogMessage "subrequest to /foo/" hook=type_checker expr=%{IS_SUBREQ}

&lt;/Location&gt;

</highlight>

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:

<highlight language="config">

LogMessage "IPv6 timeout from %{REMOTE_ADDR}" "expr=-T %{IPV6} &amp;&amp; %{REQUEST_STATUS} = 408"

</highlight>

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:

<highlight language="config">

&lt;Location "/"&gt;

&nbsp;&nbsp;LogMessage "%{reqenv:X-Foo}" hook=all

&lt;/Location&gt;

</highlight>

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>

</section>

<directivesynopsis>

<name>LogMessage</name>

<description>Log user-defined message to error log

</description>

<syntax>LogMessage <var>message</var>

[hook=<var>hook</var>] [expr=<var>expression</var>]

</syntax>

<default>Unset</default>

<contextlist><context>directory</context>

</contextlist>

<usage>

<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 border="1" style="zebra">

<columnspec><column width="1"/></columnspec>

<tr><th>Name</th></tr>

<tr><td><code>translate_name</code></td></tr>

<tr><td><code>type_checker</code></td></tr>

<tr><td><code>quick_handler</code></td></tr>

<tr><td><code>map_to_storage</code></td></tr>

<tr><td><code>check_access</code></td></tr>

<tr><td><code>check_access_ex</code></td></tr>

<tr><td><code>insert_filter</code></td></tr>

<tr><td><code>check_authn</code></td></tr>

<tr><td><code>check_authz</code></td></tr>

<tr><td><code>fixups</code></td></tr>

<tr><td><code>handler</code></td></tr>

<tr><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>

</usage>

</directivesynopsis>

</modulesynopsis>