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- --><title>Log Files - Apache HTTP Server</title><link href="./style/css/manual.css" rel="stylesheet" media="all" type="text/css" title="Main stylesheet" /><link href="./style/css/manual-loose-100pc.css" rel="alternate stylesheet" media="all" type="text/css" title="No Sidebar - Default font size" /><link href="./style/css/manual-print.css" rel="stylesheet" media="print" type="text/css" /><link href="./images/favicon.ico" rel="shortcut icon" /></head><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="./faq/">FAQ</a> | <a href="./glossary.html">Glossary</a> | <a href="./sitemap.html">Sitemap</a></p><p class="apache">Apache HTTP Server Version 2.0</p><img alt="" src="./images/feather.gif" /></div><div class="up"><a href="./"><img title="<-" alt="<-" src="./images/left.gif" /></a></div><div id="path"><a href="http://www.apache.org/">Apache</a> > <a href="http://httpd.apache.org/">HTTP Server</a> > <a href="http://httpd.apache.org/docs-project/">Documentation</a> > <a href="./">Version 2.0</a></div><div id="page-content"><div id="preamble"><h1>Log Files</h1>
+ -->
+<title>Log Files - Apache HTTP Server Version 2.5</title>
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+<p class="apache">Apache HTTP Server Version 2.5</p>
+<img alt="" src="./images/feather.gif" /></div>
+<div class="up"><a href="./"><img title="<-" alt="<-" src="./images/left.gif" /></a></div>
+<div id="path">
+<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 2.5</a></div><div id="page-content"><div id="preamble"><h1>Log Files</h1>
+<div class="toplang">
+<p><span>Available Languages: </span><a href="./en/logs.html" title="English"> en </a> |
+<a href="./fr/logs.html" hreflang="fr" rel="alternate" title="Français"> fr </a> |
+<a href="./ja/logs.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a> |
+<a href="./ko/logs.html" hreflang="ko" rel="alternate" title="Korean"> ko </a> |
+<a href="./tr/logs.html" hreflang="tr" rel="alternate" title="Türkçe"> tr </a></p>
+</div>
+
<p>In order to effectively manage a web server, it is necessary
to get feedback about the activity and performance of the
- server as well as any problems that may be occuring. The Apache
- HTTP Server provides very comprehensive and flexible logging
+ server as well as any problems that may be occurring. The Apache HTTP Server
+ provides very comprehensive and flexible logging
capabilities. This document describes how to configure its
logging capabilities, and how to understand what the logs
contain.</p>
- </div><div id="quickview"><ul id="toc"><li><img alt="" src="./images/down.gif" /> <a href="#security">Security Warning</a></li><li><img alt="" src="./images/down.gif" /> <a href="#errorlog">Error Log</a></li><li><img alt="" src="./images/down.gif" /> <a href="#accesslog">Access Log</a></li><li><img alt="" src="./images/down.gif" /> <a href="#rotation">Log Rotation</a></li><li><img alt="" src="./images/down.gif" /> <a href="#piped">Piped Logs</a></li><li><img alt="" src="./images/down.gif" /> <a href="#virtualhost">Virtual Hosts</a></li><li><img alt="" src="./images/down.gif" /> <a href="#other">Other Log Files</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="security" id="security">Security Warning</a></h2>
-
-
- <p>Anyone who can write to the directory where Apache is
+ </div>
+<div id="quickview"><ul id="toc"><li><img alt="" src="./images/down.gif" /> <a href="#overview">Overview</a></li>
+<li><img alt="" src="./images/down.gif" /> <a href="#security">Security Warning</a></li>
+<li><img alt="" src="./images/down.gif" /> <a href="#errorlog">Error Log</a></li>
+<li><img alt="" src="./images/down.gif" /> <a href="#permodule">Per-module logging</a></li>
+<li><img alt="" src="./images/down.gif" /> <a href="#accesslog">Access Log</a></li>
+<li><img alt="" src="./images/down.gif" /> <a href="#rotation">Log Rotation</a></li>
+<li><img alt="" src="./images/down.gif" /> <a href="#piped">Piped Logs</a></li>
+<li><img alt="" src="./images/down.gif" /> <a href="#virtualhost">Virtual Hosts</a></li>
+<li><img alt="" src="./images/down.gif" /> <a href="#other">Other Log Files</a></li>
+</ul><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="overview" id="overview">Overview</a></h2>
+
+
+ <table class="related"><tr><th>Related Modules</th><th>Related Directives</th></tr><tr><td><ul><li><code class="module"><a href="./mod/mod_log_config.html">mod_log_config</a></code></li><li><code class="module"><a href="./mod/mod_log_forensic.html">mod_log_forensic</a></code></li><li><code class="module"><a href="./mod/mod_logio.html">mod_logio</a></code></li><li><code class="module"><a href="./mod/mod_cgi.html">mod_cgi</a></code></li></ul></td><td /></tr></table>
+
+ <p>
+ The Apache HTTP Server provides a variety of different mechanisms for
+ logging everything that happens on your server, from the initial
+ request, through the URL mapping process, to the final resolution of
+ the connection, including any errors that may have occurred in the
+ process. In addition to this, third-party modules may provide logging
+ capabilities, or inject entries into the existing log files, and
+ applications such as CGI programs, or PHP scripts, or other handlers,
+ may send messages to the server error log.
+ </p>
+
+ <p>
+ In this document we discuss the logging modules that are a standard
+ part of the http server.
+ </p>
+
+ </div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
+<div class="section">
+<h2><a name="security" id="security">Security Warning</a></h2>
+
+
+ <p>Anyone who can write to the directory where Apache httpd is
writing a log file can almost certainly gain access to the uid
that the server is started as, which is normally root. Do
<em>NOT</em> give people write access to the directory the logs
possible for malicious clients to insert control-characters in
the log files, so care must be taken in dealing with raw
logs.</p>
- </div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div><div class="section"><h2><a name="errorlog" id="errorlog">Error Log</a></h2>
-
-
- <table class="related"><tr><th>Related Modules</th><th>Related Directives</th></tr><tr><td /><td><ul><li><code class="directive"><a href="./mod/core.html#errorlog">ErrorLog</a></code></li><li><code class="directive"><a href="./mod/core.html#loglevel">LogLevel</a></code></li></ul></td></tr></table>
+ </div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
+<div class="section">
+<h2><a name="errorlog" id="errorlog">Error Log</a></h2>
+
+ <table class="related"><tr><th>Related Modules</th><th>Related Directives</th></tr><tr><td><ul><li><code class="module"><a href="./mod/core.html">core</a></code></li></ul></td><td><ul><li><code class="directive"><a href="./mod/core.html#errorlog">ErrorLog</a></code></li><li><code class="directive"><a href="./mod/core.html#errorlogformat">ErrorLogFormat</a></code></li><li><code class="directive"><a href="./mod/core.html#loglevel">LogLevel</a></code></li></ul></td></tr></table>
+
<p>The server error log, whose name and location is set by the
<code class="directive"><a href="./mod/core.html#errorlog">ErrorLog</a></code> directive, is the
most important log file. This is the place where Apache httpd
what went wrong and how to fix it.</p>
<p>The error log is usually written to a file (typically
- <code>error_log</code> on unix systems and
- <code>error.log</code> on Windows and OS/2). On unix systems it
+ <code>error_log</code> on Unix systems and
+ <code>error.log</code> on Windows and OS/2). On Unix systems it
is also possible to have the server send errors to
<code>syslog</code> or <a href="#piped">pipe them to a
program</a>.</p>
-
- <p>The format of the error log is relatively free-form and
- descriptive. But there is certain information that is contained
- in most error log entries. For example, here is a typical
- message.</p>
-
+
+ <p>The format of the error log is defined by the <code class="directive"><a href="./mod/core.html#errorlogformat">ErrorLogFormat</a></code> directive, with which you
+ can customize what values are logged. A default is format defined
+ if you don't specify one. A typical log message follows:</p>
+
<div class="example"><p><code>
- [Wed Oct 11 14:32:52 2000] [error] [client 127.0.0.1]
- client denied by server configuration:
- /export/home/live/ap/htdocs/test
+ [Fri Sep 09 10:42:29.902022 2011] [core:error] [pid 35708:tid 4328636416]
+ [client 72.15.99.187] File does not exist: /usr/local/apache2/htdocs/favicon.ico
</code></p></div>
-
+
<p>The first item in the log entry is the date and time of the
- message. The second entry lists the severity of the error being
- reported. The <code class="directive"><a href="./mod/core.html#loglevel">LogLevel</a></code>
- directive is used to control the types of errors that are sent
- to the error log by restricting the severity level. The third
- entry gives the IP address of the client that generated the
- error. Beyond that is the message itself, which in this case
- indicates that the server has been configured to deny the
- client access. The server reports the file-system path (as
- opposed to the web path) of the requested document.</p>
+ message. The next is the module producing the message (core, in this
+ case) and the severity level of that message. This is followed by
+ the process ID and, if appropriate, the thread ID, of the process
+ that experienced the condition. Next, we have the client address
+ that made the request. And finally is the detailed error message,
+ which in this case indicates a request for a file that did not
+ exist.</p>
<p>A very wide variety of different messages can appear in the
error log. Most look similar to the example above. The error
information written to <code>stderr</code> by a CGI script will
be copied directly to the error log.</p>
- <p>It is not possible to customize the error log by adding or
- removing information. However, error log entries dealing with
- particular requests have corresponding entries in the <a href="#accesslog">access log</a>. For example, the above example
- entry corresponds to an access log entry with status code 403.
- Since it is possible to customize the access log, you can
- obtain more information about error conditions using that log
- file.</p>
-
+ <p>Putting a <code>%L</code> token in both the error log and the access
+ log will produce a log entry ID with which you can correlate the entry
+ in the error log with the entry in the access log. If
+ <code class="module"><a href="./mod/mod_unique_id.html">mod_unique_id</a></code> is loaded, its unique request ID will be
+ used as the log entry ID, too.</p>
+
<p>During testing, it is often useful to continuously monitor
- the error log for any problems. On unix systems, you can
+ the error log for any problems. On Unix systems, you can
accomplish this using:</p>
-
+
<div class="example"><p><code>
tail -f error_log
</code></p></div>
- </div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div><div class="section"><h2><a name="accesslog" id="accesslog">Access Log</a></h2>
+ </div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
+<div class="section">
+<h2><a name="permodule" id="permodule">Per-module logging</a></h2>
+
+ <p>The <code class="directive"><a href="./mod/core.html#loglevel">LogLevel</a></code> directive
+ allows you to specify a log severity level on a per-module basis. In
+ this way, if you are troubleshooting a problem with just one
+ particular module, you can turn up its logging volume without also
+ getting the details of other modules that you're not interested in.
+ This is particularly useful for modules such as
+ <code class="module"><a href="./mod/mod_proxy.html">mod_proxy</a></code> or <code class="module"><a href="./mod/mod_rewrite.html">mod_rewrite</a></code> where you
+ want to know details about what it's trying to do.</p>
+
+ <p>Do this by specifying the name of the module in your
+ <code class="directive">LogLevel</code> directive:</p>
+
+ <pre class="prettyprint lang-config">LogLevel info rewrite:trace5</pre>
+
+
+ <p>This sets the main <code class="directive">LogLevel</code> to info, but
+ turns it up to <code>trace5</code> for
+ <code class="module"><a href="./mod/mod_rewrite.html">mod_rewrite</a></code>.</p>
+
+ <div class="note">This replaces the per-module logging directives, such as
+ <code>RewriteLog</code>, that were present in earlier versions of
+ the server.</div>
+ </div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
+<div class="section">
+<h2><a name="accesslog" id="accesslog">Access Log</a></h2>
+
<table class="related"><tr><th>Related Modules</th><th>Related Directives</th></tr><tr><td><ul><li><code class="module"><a href="./mod/mod_log_config.html">mod_log_config</a></code></li><li><code class="module"><a href="./mod/mod_setenvif.html">mod_setenvif</a></code></li></ul></td><td><ul><li><code class="directive"><a href="./mod/mod_log_config.html#customlog">CustomLog</a></code></li><li><code class="directive"><a href="./mod/mod_log_config.html#logformat">LogFormat</a></code></li><li><code class="directive"><a href="./mod/mod_setenvif.html#setenvif">SetEnvIf</a></code></li></ul></td></tr></table>
-
+
<p>The server access log records all requests processed by the
server. The location and content of the access log are
controlled by the <code class="directive"><a href="./mod/mod_log_config.html#customlog">CustomLog</a></code>
directive. The <code class="directive"><a href="./mod/mod_log_config.html#logformat">LogFormat</a></code>
- directive can be used to simplify the selection of
+ directive can be used to simplify the selection of
the contents of the logs. This section describes how to configure the server
to record information in the access log.</p>
analysis, check the <a href="http://dmoz.org/Computers/Software/Internet/Site_Management/Log_analysis/">
Open Directory</a> or <a href="http://dir.yahoo.com/Computers_and_Internet/Software/Internet/World_Wide_Web/Servers/Log_Analysis_Tools/">
Yahoo</a>.</p>
-
+
<p>Various versions of Apache httpd have used other modules and
directives to control access logging, including
mod_log_referer, mod_log_agent, and the
<code>TransferLog</code> directive. The <code class="directive"><a href="./mod/mod_log_config.html#customlog">CustomLog</a></code> directive now subsumes
- the functionality of all the older directives.</p>
+ the functionality of all the older directives.</p>
<p>The format of the access log is highly configurable. The format
is specified using a format string that looks much like a C-style
printf(1) format string. Some examples are presented in the next
sections. For a complete list of the possible contents of the
format string, see the <code class="module"><a href="./mod/mod_log_config.html">mod_log_config</a></code> <a href="mod/mod_log_config.html#formats">format strings</a>.</p>
-
+
<h3><a name="common" id="common">Common Log Format</a></h3>
-
+
<p>A typical configuration for the access log might look as
follows.</p>
- <div class="example"><p><code>
- LogFormat "%h %l %u %t \"%r\" %>s %b" common<br />
- CustomLog logs/access_log common
- </code></p></div>
-
+ <pre class="prettyprint lang-config">LogFormat "%h %l %u %t \"%r\" %>s %b" common
+CustomLog logs/access_log common</pre>
+
+
<p>This defines the <em>nickname</em> <code>common</code> and
associates it with a particular log format string. The format
string consists of percent directives, each of which tell the
server to log a particular piece of information. Literal
characters may also be placed in the format string and will be
copied directly into the log output. The quote character
- (<code>"</code>) must be escaped by placing a back-slash before
+ (<code>"</code>) must be escaped by placing a backslash before
it to prevent it from being interpreted as the end of the
format string. The format string may also contain the special
control characters "<code>\n</code>" for new-line and
"<code>\t</code>" for tab.</p>
<p>The <code class="directive"><a href="./mod/mod_log_config.html#customlog">CustomLog</a></code>
- directive sets up a new log file using the defined
- <em>nickname</em>. The filename for the access log is relative to
-
the <code class="directive"><a href="./mod/core.html#serverroot">ServerRoot</a></code> unless it
- begins with a slash.</p>
-
+ directive sets up a new log file using the defined
+ <em>nickname</em>. The filename for the access log is relative to
+ the <code class="directive"><a href="./mod/core.html#serverroot">ServerRoot</a></code> unless it
+ begins with a slash.</p>
+
<p>The above configuration will write log entries in a format
known as the Common Log Format (CLF). This standard format can
be produced by many different web servers and read by many log
127.0.0.1 - frank [10/Oct/2000:13:55:36 -0700] "GET
/apache_pb.gif HTTP/1.0" 200 2326
</code></p></div>
-
+
<p>Each part of this log entry is described below.</p>
-
+
<dl>
<dt><code>127.0.0.1</code> (<code>%h</code>)</dt>
the hostname and log it in place of the IP address. However,
this configuration is not recommended since it can
significantly slow the server. Instead, it is best to use a
- log post-processor such as <a href="programs/logresolve.html">logresolve</a> to determine
+ log post-processor such as <code class="program"><a href="./programs/logresolve.html">logresolve</a></code> to determine
the hostnames. The IP address reported here is not
necessarily the address of the machine at which the user is
sitting. If a proxy server exists between the user and the
machine. This information is highly unreliable and should
almost never be used except on tightly controlled internal
networks. Apache httpd will not even attempt to determine
- this information unless <code class="directive"><a href="./mod/core.html#identitycheck">IdentityCheck</a></code> is set
+ this information unless <code class="directive"><a href="./mod/mod_ident.html#identitycheck">IdentityCheck</a></code> is set
to <code>On</code>.</dd>
<dt><code>frank</code> (<code>%u</code>)</dt>
code for the request (see below) is 401, then this value
should not be trusted because the user is not yet
authenticated. If the document is not password protected,
- this entry will be "<code>-</code>" just like the previous
+ this part will be "<code>-</code>" just like the previous
one.</dd>
<dt><code>[10/Oct/2000:13:55:36 -0700]</code>
(<code>%t</code>)</dt>
<dd>
- The time that the server finished processing the request.
- The format is:
+ The time that the request was received.
+ The format is:
<p class="indent">
<code>[day/month/year:hour:minute:second zone]<br />
second = 2*digit<br />
zone = (`+' | `-') 4*digit</code>
</p>
- It is possible to have the time displayed in another format
+ <p>It is possible to have the time displayed in another format
by specifying <code>%{format}t</code> in the log format
- string, where <code>format</code> is as in
- <code>strftime(3)</code> from the C standard library.
+ string, where <code>format</code> is either as in
+ <code>strftime(3)</code> from the C standard library,
+ or one of the supported special tokens. For details see
+ the <code class="module"><a href="./mod/mod_log_config.html">mod_log_config</a></code> <a href="mod/mod_log_config.html#formats">format strings</a>.</p>
</dd>
<dt><code>"GET /apache_pb.gif HTTP/1.0"</code>
<dt><code>2326</code> (<code>%b</code>)</dt>
- <dd>The last entry indicates the size of the object returned
+ <dd>The last part indicates the size of the object returned
to the client, not including the response headers. If no
content was returned to the client, this value will be
"<code>-</code>". To log "<code>0</code>" for no content, use
<code>%B</code> instead.</dd>
</dl>
-
+
<h3><a name="combined" id="combined">Combined Log Format</a></h3>
-
+
<p>Another commonly used format string is called the Combined
Log Format. It can be used as follows.</p>
- <div class="example"><p><code>
- LogFormat "%h %l %u %t \"%r\" %>s %b \"%{Referer}i\"
- \"%{User-agent}i\"" combined<br />
- CustomLog log/acces_log combined
- </code></p></div>
+ <pre class="prettyprint lang-config">LogFormat "%h %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-agent}i\"" combined
+CustomLog log/access_log combined</pre>
+
<p>This format is exactly the same as the Common Log Format,
with the addition of two more fields. Each of the additional
<code>%{<em>header</em>}i</code>, where <em>header</em> can be
any HTTP request header. The access log under this format will
look like:</p>
-
+
<div class="example"><p><code>
127.0.0.1 - frank [10/Oct/2000:13:55:36 -0700] "GET
/apache_pb.gif HTTP/1.0" 200 2326
</code></p></div>
<p>The additional fields are:</p>
-
+
<dl>
<dt><code>"http://www.example.com/start.html"</code>
(<code>\"%{Referer}i\"</code>)</dt>
itself.</dd>
</dl>
-
+
<h3><a name="multiple" id="multiple">Multiple Access Logs</a></h3>
-
+
<p>Multiple access logs can be created simply by specifying
- multiple <code class="directive"><a href="./mod/mod_log_config.html#customlog">CustomLog</a></code>
+ multiple <code class="directive"><a href="./mod/mod_log_config.html#customlog">CustomLog</a></code>
directives in the configuration
file. For example, the following directives will create three
access logs. The first contains the basic CLF information,
information. The last two <code class="directive"><a href="./mod/mod_log_config.html#customlog">CustomLog</a></code> lines show how
to mimic the effects of the <code>ReferLog</code> and <code>AgentLog</code> directives.</p>
- <div class="example"><p><code>
- LogFormat "%h %l %u %t \"%r\" %>s %b" common<br />
- CustomLog logs/access_log common<br />
- CustomLog logs/referer_log "%{Referer}i -> %U"<br />
- CustomLog logs/agent_log "%{User-agent}i"
- </code></p></div>
+ <pre class="prettyprint lang-config">LogFormat "%h %l %u %t \"%r\" %>s %b" common
+CustomLog logs/access_log common
+CustomLog logs/referer_log "%{Referer}i -> %U"
+CustomLog logs/agent_log "%{User-agent}i"</pre>
+
<p>This example also shows that it is not necessary to define a
nickname with the <code class="directive"><a href="./mod/mod_log_config.html#logformat">LogFormat</a></code> directive. Instead,
the log format can be specified directly in the <code class="directive"><a href="./mod/mod_log_config.html#customlog">CustomLog</a></code> directive.</p>
-
+
<h3><a name="conditional" id="conditional">Conditional Logs</a></h3>
-
+
<p>There are times when it is convenient to exclude certain
entries from the access logs based on characteristics of the
client request. This is easily accomplished with the help of <a href="env.html">environment variables</a>. First, an
environment variable must be set to indicate that the request
- meets certain conditions. This is usually accomplished with
+ meets certain conditions. This is usually accomplished with
<code class="directive"><a href="./mod/mod_setenvif.html#setenvif">SetEnvIf</a></code>. Then the
<code>env=</code> clause of the <code class="directive"><a href="./mod/mod_log_config.html#customlog">CustomLog</a></code> directive is used to
- include or exclude requests where the environment variable is
- set. Some examples:</p>
+ include or exclude requests where the environment variable is
+ set. Some examples:</p>
+
+ <pre class="prettyprint lang-config"># Mark requests from the loop-back interface
+SetEnvIf Remote_Addr "127\.0\.0\.1" dontlog
+# Mark requests for the robots.txt file
+SetEnvIf Request_URI "^/robots\.txt$" dontlog
+# Log what remains
+CustomLog logs/access_log common env=!dontlog</pre>
- <div class="example"><p><code>
- # Mark requests from the loop-back interface<br />
- SetEnvIf Remote_Addr "127\.0\.0\.1" dontlog<br />
- # Mark requests for the robots.txt file<br />
- SetEnvIf Request_URI "^/robots\.txt$" dontlog<br />
- # Log what remains<br />
- CustomLog logs/access_log common env=!dontlog
- </code></p></div>
<p>As another example, consider logging requests from
english-speakers to one log file, and non-english speakers to a
different log file.</p>
- <div class="example"><p><code>
- SetEnvIf Accept-Language "en" english<br />
+ <pre class="prettyprint lang-config"> SetEnvIf Accept-Language "en" english<br />
CustomLog logs/english_log common env=english<br />
- CustomLog logs/non_english_log common env=!english
- </code></p></div>
+ CustomLog logs/non_english_log common env=!english</pre>
+
+
+ <p>In a caching scenario one would want to know about
+ the efficiency of the cache. A very simple method to
+ find this out would be:</p>
+
+ <pre class="prettyprint lang-config">SetEnv CACHE_MISS 1
+LogFormat "%h %l %u %t "%r " %>s %b %{CACHE_MISS}e" common-cache
+CustomLog logs/access_log common-cache</pre>
+
+
+ <p><code class="module"><a href="./mod/mod_cache.html">mod_cache</a></code> will run before
+ <code class="module"><a href="./mod/mod_env.html">mod_env</a></code> and, when successful, will deliver the
+ content without it. In that case a cache hit will log
+ <code>-</code>, while a cache miss will log <code>1</code>.</p>
+
+ <p>In addition to the <code>env=</code> syntax, <code class="directive"><a href="./mod/mod_log_config.html#logformat">LogFormat</a></code> supports logging values
+ conditional upon the HTTP response code:</p>
+
+ <pre class="prettyprint lang-config">LogFormat "%400,501{User-agent}i" browserlog
+LogFormat "%!200,304,302{Referer}i" refererlog</pre>
+
+
+ <p>In the first example, the <code>User-agent</code> will be
+ logged if the HTTP status code is 400 or 501. In other cases, a
+ literal "-" will be logged instead. Likewise, in the second
+ example, the <code>Referer</code> will be logged if the HTTP
+ status code is <strong>not</strong> 200, 204, or 302. (Note the
+ "!" before the status codes.</p>
<p>Although we have just shown that conditional logging is very
- powerful and flexibly, it is not the only way to control the
+ powerful and flexible, it is not the only way to control the
contents of the logs. Log files are more useful when they
contain a complete record of server activity. It is often
easier to simply post-process the log files to remove requests
that you do not want to consider.</p>
- </div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div><div class="section"><h2><a name="rotation" id="rotation">Log Rotation</a></h2>
-
+ </div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
+<div class="section">
+<h2><a name="rotation" id="rotation">Log Rotation</a></h2>
+
<p>On even a moderately busy server, the quantity of
information stored in the log files is very large. The access
log file typically grows 1 MB or more per 10,000 requests. It
will consequently be necessary to periodically rotate the log
files by moving or deleting the existing logs. This cannot be
- done while the server is running, because Apache will continue
+ done while the server is running, because Apache httpd will continue
writing to the old log file as long as it holds the file open.
Instead, the server must be <a href="stopping.html">restarted</a> after the log files are
moved or deleted so that it will open new log files.</p>
<p>Another way to perform log rotation is using <a href="#piped">piped logs</a> as discussed in the next
section.</p>
- </div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div><div class="section"><h2><a name="piped" id="piped">Piped Logs</a></h2>
-
+ </div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
+<div class="section">
+<h2><a name="piped" id="piped">Piped Logs</a></h2>
+
<p>Apache httpd is capable of writing error and access log
files through a pipe to another process, rather than directly
to a file. This capability dramatically increases the
In order to write logs to a pipe, simply replace the filename
with the pipe character "<code>|</code>", followed by the name
of the executable which should accept log entries on its
- standard input. Apache will start the piped-log process when
+ standard input. The server will start the piped-log process when
the server starts, and will restart it if it crashes while the
server is running. (This last feature is why we can refer to
this technique as "reliable piped logging".)</p>
<p>One important use of piped logs is to allow log rotation
without having to restart the server. The Apache HTTP Server
- includes a simple program called <a href="programs/rotatelogs.html">rotatelogs</a> for this
- purpose. For example, to rotate the logs every 24 hours, you
+ includes a simple program called <code class="program"><a href="./programs/rotatelogs.html">rotatelogs</a></code>
+ for this purpose. For example, to rotate the logs every 24 hours, you
can use:</p>
- <div class="example"><p><code>
- CustomLog "|/usr/local/apache/bin/rotatelogs
- /var/log/access_log 86400" common
- </code></p></div>
-
+ <pre class="prettyprint lang-config">CustomLog "|/usr/local/apache/bin/rotatelogs /var/log/access_log 86400" common</pre>
+
+
<p>Notice that quotes are used to enclose the entire command
that will be called for the pipe. Although these examples are
for the access log, the same technique can be used for the
error log.</p>
- <p>A similar, but much more flexible log rotation program
+ <p>A similar but much more flexible log rotation program
called <a href="http://www.cronolog.org/">cronolog</a>
is available at an external site.</p>
<p>As with conditional logging, piped logs are a very powerful
tool, but they should not be used where a simpler solution like
off-line post-processing is available.</p>
- </div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div><div class="section"><h2><a name="virtualhost" id="virtualhost">Virtual Hosts</a></h2>
-
+
+ <p>By default the piped log process is spawned without invoking
+ a shell. Use "<code>|$</code>" instead of "<code>|</code>"
+ to spawn using a shell (usually with <code>/bin/sh -c</code>):</p>
+
+ <pre class="prettyprint lang-config"># Invoke "rotatelogs" using a shell
+CustomLog "|$/usr/local/apache/bin/rotatelogs /var/log/access_log 86400" common</pre>
+
+
+ <p>This was the default behaviour for Apache 2.2.
+ Depending on the shell specifics this might lead to
+ an additional shell process for the lifetime of the logging
+ pipe program and signal handling problems during restart.
+ For compatibility reasons with Apache 2.2 the notation
+ "<code>||</code>" is also supported and equivalent to using
+ "<code>|</code>".</p>
+ </div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
+<div class="section">
+<h2><a name="virtualhost" id="virtualhost">Virtual Hosts</a></h2>
+
<p>When running a server with many <a href="vhosts/">virtual
hosts</a>, there are several options for dealing with log
files. First, it is possible to use logs exactly as in a
for easy collection of statistics on individual virtual
hosts.</p>
- <p>If <code class="directive"><a href="./mod/mod_log_config.html#customlog">CustomLog</a></code>
+ <p>If <code class="directive"><a href="./mod/mod_log_config.html#customlog">CustomLog</a></code>
or <code class="directive"><a href="./mod/core.html#errorlog">ErrorLog</a></code>
directives are placed inside a
<code class="directive"><a href="./mod/core.html#virtualhost"><VirtualHost></a></code>
later split the log into individual files. For example,
consider the following directives.</p>
- <div class="example"><p><code>
- LogFormat "%v %l %u %t \"%r\" %>s %b"
- comonvhost<br />
- CustomLog logs/access_log comonvhost
- </code></p></div>
+ <pre class="prettyprint lang-config">LogFormat "%v %l %u %t \"%r\" %>s %b" comonvhost
+CustomLog logs/access_log comonvhost</pre>
+
<p>The <code>%v</code> is used to log the name of the virtual
- host that is serving the request. Then a program like <a href="programs/other.html">split-logfile</a> can be used to
+ host that is serving the request. Then a program like <a href="programs/split-logfile.html">split-logfile</a> can be used to
post-process the access log in order to split it into one file
per virtual host.</p>
- </div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div><div class="section"><h2><a name="other" id="other">Other Log Files</a></h2>
+ </div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
+<div class="section">
+<h2><a name="other" id="other">Other Log Files</a></h2>
+
+ <table class="related"><tr><th>Related Modules</th><th>Related Directives</th></tr><tr><td><ul><li><code class="module"><a href="./mod/mod_logio.html">mod_logio</a></code></li><li><code class="module"><a href="./mod/mod_log_config.html">mod_log_config</a></code></li><li><code class="module"><a href="./mod/mod_log_forensic.html">mod_log_forensic</a></code></li><li><code class="module"><a href="./mod/mod_cgi.html">mod_cgi</a></code></li></ul></td><td><ul><li><code class="directive"><a href="./mod/mod_log_config.html#logformat">LogFormat</a></code></li><li><code class="directive"><a href="./mod/mod_log_config.html#bufferedlogs">BufferedLogs</a></code></li><li><code class="directive"><a href="./mod/mod_log_forensic.html#forensiclog">ForensicLog</a></code></li><li><code class="directive"><a href="./mod/mpm_common.html#pidfile">PidFile</a></code></li><li><code class="directive"><a href="./mod/mod_cgi.html#scriptlog">ScriptLog</a></code></li><li><code class="directive"><a href="./mod/mod_cgi.html#scriptlogbuffer">ScriptLogBuffer</a></code></li><li><code class="directive"><a href="./mod/mod_cgi.html#scriptloglength">ScriptLogLength</a></code></li></ul></td></tr></table>
+
+ <h3>Logging actual bytes sent and received</h3>
+
+
+ <p><code class="module"><a href="./mod/mod_logio.html">mod_logio</a></code> adds in two additional
+ <code class="directive"><a href="./mod/mod_log_config.html#logformat">LogFormat</a></code> fields
+ (%I and %O) that log the actual number of bytes received and sent
+ on the network.</p>
- <table class="related"><tr><th>Related Modules</th><th>Related Directives</th></tr><tr><td><ul><li><code class="module"><a href="./mod/mod_cgi.html">mod_cgi</a></code></li><li><code class="module"><a href="./mod/mod_rewrite.html">mod_rewrite</a></code></li></ul></td><td><ul><li><code class="directive"><a href="./mod/mpm_common.html#pidfile">PidFile</a></code></li><li><code class="directive"><a href="./mod/mod_rewrite.html#rewritelog">RewriteLog</a></code></li><li><code class="directive"><a href="./mod/mod_rewrite.html#rewriteloglevel">RewriteLogLevel</a></code></li><li><code class="directive"><a href="./mod/mod_cgi.html#scriptlog">ScriptLog</a></code></li><li><code class="directive"><a href="./mod/mod_cgi.html#scriptlogbuffer">ScriptLogBuffer</a></code></li><li><code class="directive"><a href="./mod/mod_cgi.html#scriptloglength">ScriptLogLength</a></code></li></ul></td></tr></table>
+
+ <h3>Forensic Logging</h3>
+
+
+ <p><code class="module"><a href="./mod/mod_log_forensic.html">mod_log_forensic</a></code> provides for forensic logging of
+ client requests. Logging is done before and after processing a
+ request, so the forensic log contains two log lines for each
+ request. The forensic logger is very strict with no customizations.
+ It can be an invaluable debugging and security tool.</p>
+
<h3><a name="pidfile" id="pidfile">PID File</a></h3>
-
+
<p>On startup, Apache httpd saves the process id of the parent
httpd process to the file <code>logs/httpd.pid</code>. This
filename can be changed with the <code class="directive"><a href="./mod/mpm_common.html#pidfile">PidFile</a></code> directive. The
terminating the daemon by sending signals to the parent
process; on Windows, use the -k command line option instead.
For more information see the <a href="stopping.html">Stopping
- and Restarting</a> page.</p>
-
+ and Restarting</a> page.</p>
+
<h3><a name="scriptlog" id="scriptlog">Script Log</a></h3>
-
+
<p>In order to aid in debugging, the
<code class="directive"><a href="./mod/mod_cgi.html#scriptlog">ScriptLog</a></code> directive
allows you to record the input to and output from CGI scripts.
This should only be used in testing - not for live servers.
More information is available in the <a href="mod/mod_cgi.html">mod_cgi</a> documentation.</p>
-
- <h3><a name="rewritelog" id="rewritelog">Rewrite Log</a></h3>
-
-
- <p>When using the powerful and complex features of <a href="mod/mod_rewrite.html">mod_rewrite</a>, it is almost
- always necessary to use the <code class="directive"><a href="./mod/mod_rewrite.html#rewritelog">RewriteLog</a></code> to help
- in debugging. This log file produces a detailed analysis of how
- the rewriting engine transforms requests. The level of detail
- is controlled by the <code class="directive"><a href="./mod/mod_rewrite.html#rewriteloglevel">RewriteLogLevel</a></code> directive.</p>
-
- </div></div><div id="footer"><p class="apache">Maintained by the <a href="http://httpd.apache.org/docs-project/">Apache HTTP Server Documentation Project</a></p><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></div></body></html>
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+
+ </div></div>
+<div class="bottomlang">
+<p><span>Available Languages: </span><a href="./en/logs.html" title="English"> en </a> |
+<a href="./fr/logs.html" hreflang="fr" rel="alternate" title="Français"> fr </a> |
+<a href="./ja/logs.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a> |
+<a href="./ko/logs.html" hreflang="ko" rel="alternate" title="Korean"> ko </a> |
+<a href="./tr/logs.html" hreflang="tr" rel="alternate" title="Türkçe"> tr </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&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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