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18 <p class="apache">Apache HTTP Server Version 2.5</p>
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31 <p>In order to effectively manage a web server, it is necessary
32 to get feedback about the activity and performance of the
33 server as well as any problems that may be occurring. The Apache HTTP Server
34 provides very comprehensive and flexible logging
35 capabilities. This document describes how to configure its
36 logging capabilities, and how to understand what the logs
39 <div id="quickview"><ul id="toc"><li><img alt="" src="./images/down.gif" /> <a href="#overview">Overview</a></li>
40 <li><img alt="" src="./images/down.gif" /> <a href="#security">Security Warning</a></li>
41 <li><img alt="" src="./images/down.gif" /> <a href="#errorlog">Error Log</a></li>
42 <li><img alt="" src="./images/down.gif" /> <a href="#permodule">Per-module logging</a></li>
43 <li><img alt="" src="./images/down.gif" /> <a href="#accesslog">Access Log</a></li>
44 <li><img alt="" src="./images/down.gif" /> <a href="#rotation">Log Rotation</a></li>
45 <li><img alt="" src="./images/down.gif" /> <a href="#piped">Piped Logs</a></li>
46 <li><img alt="" src="./images/down.gif" /> <a href="#virtualhost">Virtual Hosts</a></li>
47 <li><img alt="" src="./images/down.gif" /> <a href="#other">Other Log Files</a></li>
48 </ul><ul class="seealso"><li><a href="#comments_section">Comments</a></li></ul></div>
49 <div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
51 <h2><a name="overview" id="overview">Overview</a></h2>
54 <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>
57 The Apache HTTP Server provides a variety of different mechanisms for
58 logging everything that happens on your server, from the initial
59 request, through the URL mapping process, to the final resolution of
60 the connection, including any errors that may have occurred in the
61 process. In addition to this, third-party modules may provide logging
62 capabilities, or inject entries into the existing log files, and
63 applications such as CGI programs, or PHP scripts, or other handlers,
64 may send messages to the server error log.
68 In this document we discuss the logging modules that are a standard
69 part of the http server.
72 </div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
74 <h2><a name="security" id="security">Security Warning</a></h2>
77 <p>Anyone who can write to the directory where Apache httpd is
78 writing a log file can almost certainly gain access to the uid
79 that the server is started as, which is normally root. Do
80 <em>NOT</em> give people write access to the directory the logs
81 are stored in without being aware of the consequences; see the
82 <a href="misc/security_tips.html">security tips</a> document
85 <p>In addition, log files may contain information supplied
86 directly by the client, without escaping. Therefore, it is
87 possible for malicious clients to insert control-characters in
88 the log files, so care must be taken in dealing with raw
90 </div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
92 <h2><a name="errorlog" id="errorlog">Error Log</a></h2>
95 <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>
97 <p>The server error log, whose name and location is set by the
98 <code class="directive"><a href="./mod/core.html#errorlog">ErrorLog</a></code> directive, is the
99 most important log file. This is the place where Apache httpd
100 will send diagnostic information and record any errors that it
101 encounters in processing requests. It is the first place to
102 look when a problem occurs with starting the server or with the
103 operation of the server, since it will often contain details of
104 what went wrong and how to fix it.</p>
106 <p>The error log is usually written to a file (typically
107 <code>error_log</code> on Unix systems and
108 <code>error.log</code> on Windows and OS/2). On Unix systems it
109 is also possible to have the server send errors to
110 <code>syslog</code> or <a href="#piped">pipe them to a
113 <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
114 can customize what values are logged. A default is format defined
115 if you don't specify one. A typical log message follows:</p>
117 <div class="example"><p><code>
118 [Fri Sep 09 10:42:29.902022 2011] [core:error] [pid 35708:tid 4328636416]
119 [client 72.15.99.187] File does not exist: /usr/local/apache2/htdocs/favicon.ico
122 <p>The first item in the log entry is the date and time of the
123 message. The next is the module producing the message (core, in this
124 case) and the severity level of that message. This is followed by
125 the process ID and, if appropriate, the thread ID, of the process
126 that experienced the condition. Next, we have the client address
127 that made the request. And finally is the detailed error message,
128 which in this case indicates a request for a file that did not
131 <p>A very wide variety of different messages can appear in the
132 error log. Most look similar to the example above. The error
133 log will also contain debugging output from CGI scripts. Any
134 information written to <code>stderr</code> by a CGI script will
135 be copied directly to the error log.</p>
137 <p>Putting a <code>%L</code> token in both the error log and the access
138 log will produce a log entry ID with which you can correlate the entry
139 in the error log with the entry in the access log. If
140 <code class="module"><a href="./mod/mod_unique_id.html">mod_unique_id</a></code> is loaded, its unique request ID will be
141 used as the log entry ID, too.</p>
143 <p>During testing, it is often useful to continuously monitor
144 the error log for any problems. On Unix systems, you can
145 accomplish this using:</p>
147 <div class="example"><p><code>
150 </div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
151 <div class="section">
152 <h2><a name="permodule" id="permodule">Per-module logging</a></h2>
155 <p>The <code class="directive"><a href="./mod/core.html#loglevel">LogLevel</a></code> directive
156 allows you to specify a log severity level on a per-module basis. In
157 this way, if you are troubleshooting a problem with just one
158 particular module, you can turn up its logging volume without also
159 getting the details of other modules that you're not interested in.
160 This is particularly useful for modules such as
161 <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
162 want to know details about what it's trying to do.</p>
164 <p>Do this by specifying the name of the module in your
165 <code class="directive">LogLevel</code> directive:</p>
167 <pre class="prettyprint lang-config">
168 LogLevel info rewrite:trace5
172 <p>This sets the main <code class="directive">LogLevel</code> to info, but
173 turns it up to <code>trace5</code> for
174 <code class="module"><a href="./mod/mod_rewrite.html">mod_rewrite</a></code>.</p>
176 <div class="note">This replaces the per-module logging directives, such as
177 <code>RewriteLog</code>, that were present in earlier versions of
179 </div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
180 <div class="section">
181 <h2><a name="accesslog" id="accesslog">Access Log</a></h2>
184 <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>
186 <p>The server access log records all requests processed by the
187 server. The location and content of the access log are
188 controlled by the <code class="directive"><a href="./mod/mod_log_config.html#customlog">CustomLog</a></code>
189 directive. The <code class="directive"><a href="./mod/mod_log_config.html#logformat">LogFormat</a></code>
190 directive can be used to simplify the selection of
191 the contents of the logs. This section describes how to configure the server
192 to record information in the access log.</p>
194 <p>Of course, storing the information in the access log is only
195 the start of log management. The next step is to analyze this
196 information to produce useful statistics. Log analysis in
197 general is beyond the scope of this document, and not really
198 part of the job of the web server itself. For more information
199 about this topic, and for applications which perform log
200 analysis, check the <a href="http://dmoz.org/Computers/Software/Internet/Site_Management/Log_analysis/">
201 Open Directory</a> or <a href="http://dir.yahoo.com/Computers_and_Internet/Software/Internet/World_Wide_Web/Servers/Log_Analysis_Tools/">
204 <p>Various versions of Apache httpd have used other modules and
205 directives to control access logging, including
206 mod_log_referer, mod_log_agent, and the
207 <code>TransferLog</code> directive. The <code class="directive"><a href="./mod/mod_log_config.html#customlog">CustomLog</a></code> directive now subsumes
208 the functionality of all the older directives.</p>
210 <p>The format of the access log is highly configurable. The format
211 is specified using a format string that looks much like a C-style
212 printf(1) format string. Some examples are presented in the next
213 sections. For a complete list of the possible contents of the
214 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>
216 <h3><a name="common" id="common">Common Log Format</a></h3>
219 <p>A typical configuration for the access log might look as
222 <pre class="prettyprint lang-config">
223 LogFormat "%h %l %u %t \"%r\" %>s %b" common
224 CustomLog logs/access_log common
228 <p>This defines the <em>nickname</em> <code>common</code> and
229 associates it with a particular log format string. The format
230 string consists of percent directives, each of which tell the
231 server to log a particular piece of information. Literal
232 characters may also be placed in the format string and will be
233 copied directly into the log output. The quote character
234 (<code>"</code>) must be escaped by placing a backslash before
235 it to prevent it from being interpreted as the end of the
236 format string. The format string may also contain the special
237 control characters "<code>\n</code>" for new-line and
238 "<code>\t</code>" for tab.</p>
240 <p>The <code class="directive"><a href="./mod/mod_log_config.html#customlog">CustomLog</a></code>
241 directive sets up a new log file using the defined
242 <em>nickname</em>. The filename for the access log is relative to
243 the <code class="directive"><a href="./mod/core.html#serverroot">ServerRoot</a></code> unless it
244 begins with a slash.</p>
246 <p>The above configuration will write log entries in a format
247 known as the Common Log Format (CLF). This standard format can
248 be produced by many different web servers and read by many log
249 analysis programs. The log file entries produced in CLF will
250 look something like this:</p>
252 <div class="example"><p><code>
253 127.0.0.1 - frank [10/Oct/2000:13:55:36 -0700] "GET
254 /apache_pb.gif HTTP/1.0" 200 2326
257 <p>Each part of this log entry is described below.</p>
260 <dt><code>127.0.0.1</code> (<code>%h</code>)</dt>
262 <dd>This is the IP address of the client (remote host) which
263 made the request to the server. If <code class="directive"><a href="./mod/core.html#hostnamelookups">HostnameLookups</a></code> is
264 set to <code>On</code>, then the server will try to determine
265 the hostname and log it in place of the IP address. However,
266 this configuration is not recommended since it can
267 significantly slow the server. Instead, it is best to use a
268 log post-processor such as <code class="program"><a href="./programs/logresolve.html">logresolve</a></code> to determine
269 the hostnames. The IP address reported here is not
270 necessarily the address of the machine at which the user is
271 sitting. If a proxy server exists between the user and the
272 server, this address will be the address of the proxy, rather
273 than the originating machine.</dd>
275 <dt><code>-</code> (<code>%l</code>)</dt>
277 <dd>The "hyphen" in the output indicates that the requested
278 piece of information is not available. In this case, the
279 information that is not available is the RFC 1413 identity of
280 the client determined by <code>identd</code> on the clients
281 machine. This information is highly unreliable and should
282 almost never be used except on tightly controlled internal
283 networks. Apache httpd will not even attempt to determine
284 this information unless <code class="directive"><a href="./mod/mod_ident.html#identitycheck">IdentityCheck</a></code> is set
285 to <code>On</code>.</dd>
287 <dt><code>frank</code> (<code>%u</code>)</dt>
289 <dd>This is the userid of the person requesting the document
290 as determined by HTTP authentication. The same value is
291 typically provided to CGI scripts in the
292 <code>REMOTE_USER</code> environment variable. If the status
293 code for the request (see below) is 401, then this value
294 should not be trusted because the user is not yet
295 authenticated. If the document is not password protected,
296 this part will be "<code>-</code>" just like the previous
299 <dt><code>[10/Oct/2000:13:55:36 -0700]</code>
300 (<code>%t</code>)</dt>
303 The time that the request was received.
307 <code>[day/month/year:hour:minute:second zone]<br />
309 month = 3*letter<br />
312 minute = 2*digit<br />
313 second = 2*digit<br />
314 zone = (`+' | `-') 4*digit</code>
316 <p>It is possible to have the time displayed in another format
317 by specifying <code>%{format}t</code> in the log format
318 string, where <code>format</code> is either as in
319 <code>strftime(3)</code> from the C standard library,
320 or one of the supported special tokens. For details see
321 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>
324 <dt><code>"GET /apache_pb.gif HTTP/1.0"</code>
325 (<code>\"%r\"</code>)</dt>
327 <dd>The request line from the client is given in double
328 quotes. The request line contains a great deal of useful
329 information. First, the method used by the client is
330 <code>GET</code>. Second, the client requested the resource
331 <code>/apache_pb.gif</code>, and third, the client used the
332 protocol <code>HTTP/1.0</code>. It is also possible to log
333 one or more parts of the request line independently. For
334 example, the format string "<code>%m %U%q %H</code>" will log
335 the method, path, query-string, and protocol, resulting in
336 exactly the same output as "<code>%r</code>".</dd>
338 <dt><code>200</code> (<code>%>s</code>)</dt>
340 <dd>This is the status code that the server sends back to the
341 client. This information is very valuable, because it reveals
342 whether the request resulted in a successful response (codes
343 beginning in 2), a redirection (codes beginning in 3), an
344 error caused by the client (codes beginning in 4), or an
345 error in the server (codes beginning in 5). The full list of
346 possible status codes can be found in the <a href="http://www.w3.org/Protocols/rfc2616/rfc2616.txt">HTTP
347 specification</a> (RFC2616 section 10).</dd>
349 <dt><code>2326</code> (<code>%b</code>)</dt>
351 <dd>The last part indicates the size of the object returned
352 to the client, not including the response headers. If no
353 content was returned to the client, this value will be
354 "<code>-</code>". To log "<code>0</code>" for no content, use
355 <code>%B</code> instead.</dd>
359 <h3><a name="combined" id="combined">Combined Log Format</a></h3>
362 <p>Another commonly used format string is called the Combined
363 Log Format. It can be used as follows.</p>
365 <pre class="prettyprint lang-config">
366 LogFormat "%h %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-agent}i\"" combined
367 CustomLog log/access_log combined
371 <p>This format is exactly the same as the Common Log Format,
372 with the addition of two more fields. Each of the additional
373 fields uses the percent-directive
374 <code>%{<em>header</em>}i</code>, where <em>header</em> can be
375 any HTTP request header. The access log under this format will
378 <div class="example"><p><code>
379 127.0.0.1 - frank [10/Oct/2000:13:55:36 -0700] "GET
380 /apache_pb.gif HTTP/1.0" 200 2326
381 "http://www.example.com/start.html" "Mozilla/4.08 [en]
385 <p>The additional fields are:</p>
388 <dt><code>"http://www.example.com/start.html"</code>
389 (<code>\"%{Referer}i\"</code>)</dt>
391 <dd>The "Referer" (sic) HTTP request header. This gives the
392 site that the client reports having been referred from. (This
393 should be the page that links to or includes
394 <code>/apache_pb.gif</code>).</dd>
396 <dt><code>"Mozilla/4.08 [en] (Win98; I ;Nav)"</code>
397 (<code>\"%{User-agent}i\"</code>)</dt>
399 <dd>The User-Agent HTTP request header. This is the
400 identifying information that the client browser reports about
405 <h3><a name="multiple" id="multiple">Multiple Access Logs</a></h3>
408 <p>Multiple access logs can be created simply by specifying
409 multiple <code class="directive"><a href="./mod/mod_log_config.html#customlog">CustomLog</a></code>
410 directives in the configuration
411 file. For example, the following directives will create three
412 access logs. The first contains the basic CLF information,
413 while the second and third contain referer and browser
414 information. The last two <code class="directive"><a href="./mod/mod_log_config.html#customlog">CustomLog</a></code> lines show how
415 to mimic the effects of the <code>ReferLog</code> and <code>AgentLog</code> directives.</p>
417 <pre class="prettyprint lang-config">
418 LogFormat "%h %l %u %t \"%r\" %>s %b" common
419 CustomLog logs/access_log common
420 CustomLog logs/referer_log "%{Referer}i -> %U"
421 CustomLog logs/agent_log "%{User-agent}i"
425 <p>This example also shows that it is not necessary to define a
426 nickname with the <code class="directive"><a href="./mod/mod_log_config.html#logformat">LogFormat</a></code> directive. Instead,
427 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>
430 <h3><a name="conditional" id="conditional">Conditional Logs</a></h3>
433 <p>There are times when it is convenient to exclude certain
434 entries from the access logs based on characteristics of the
435 client request. This is easily accomplished with the help of <a href="env.html">environment variables</a>. First, an
436 environment variable must be set to indicate that the request
437 meets certain conditions. This is usually accomplished with
438 <code class="directive"><a href="./mod/mod_setenvif.html#setenvif">SetEnvIf</a></code>. Then the
439 <code>env=</code> clause of the <code class="directive"><a href="./mod/mod_log_config.html#customlog">CustomLog</a></code> directive is used to
440 include or exclude requests where the environment variable is
441 set. Some examples:</p>
443 <pre class="prettyprint lang-config">
444 # Mark requests from the loop-back interface
445 SetEnvIf Remote_Addr "127\.0\.0\.1" dontlog
446 # Mark requests for the robots.txt file
447 SetEnvIf Request_URI "^/robots\.txt$" dontlog
449 CustomLog logs/access_log common env=!dontlog
453 <p>As another example, consider logging requests from
454 english-speakers to one log file, and non-english speakers to a
455 different log file.</p>
457 <pre class="prettyprint lang-config">
458 SetEnvIf Accept-Language "en" english<br />
459 CustomLog logs/english_log common env=english<br />
460 CustomLog logs/non_english_log common env=!english
464 <p>In a caching scenario one would want to know about
465 the efficiency of the cache. A very simple method to
466 find this out would be:</p>
468 <pre class="prettyprint lang-config">
470 LogFormat "%h %l %u %t "%r " %>s %b %{CACHE_MISS}e" common-cache
471 CustomLog logs/access_log common-cache
475 <p><code class="module"><a href="./mod/mod_cache.html">mod_cache</a></code> will run before
476 <code class="module"><a href="./mod/mod_env.html">mod_env</a></code> and when successfull will deliver the
477 content without it. In that case a cache hit will log
478 <code>-</code>, while a cache miss will log <code>1</code>.</p>
480 <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
481 conditional upon the HTTP response code:</p>
483 <pre class="prettyprint lang-config">
484 LogFormat "%400,501{User-agent}i" browserlog
485 LogFormat "%!200,304,302{Referer}i" refererlog
489 <p>In the first example, the <code>User-agent</code> will be
490 logged if the HTTP status code is 400 or 501. In other cases, a
491 literal "-" will be logged instead. Likewise, in the second
492 example, the <code>Referer</code> will be logged if the HTTP
493 status code is <strong>not</strong> 200, 204, or 302. (Note the
494 "!" before the status codes.</p>
496 <p>Although we have just shown that conditional logging is very
497 powerful and flexible, it is not the only way to control the
498 contents of the logs. Log files are more useful when they
499 contain a complete record of server activity. It is often
500 easier to simply post-process the log files to remove requests
501 that you do not want to consider.</p>
503 </div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
504 <div class="section">
505 <h2><a name="rotation" id="rotation">Log Rotation</a></h2>
508 <p>On even a moderately busy server, the quantity of
509 information stored in the log files is very large. The access
510 log file typically grows 1 MB or more per 10,000 requests. It
511 will consequently be necessary to periodically rotate the log
512 files by moving or deleting the existing logs. This cannot be
513 done while the server is running, because Apache httpd will continue
514 writing to the old log file as long as it holds the file open.
515 Instead, the server must be <a href="stopping.html">restarted</a> after the log files are
516 moved or deleted so that it will open new log files.</p>
518 <p>By using a <em>graceful</em> restart, the server can be
519 instructed to open new log files without losing any existing or
520 pending connections from clients. However, in order to
521 accomplish this, the server must continue to write to the old
522 log files while it finishes serving old requests. It is
523 therefore necessary to wait for some time after the restart
524 before doing any processing on the log files. A typical
525 scenario that simply rotates the logs and compresses the old
526 logs to save space is:</p>
528 <div class="example"><p><code>
529 mv access_log access_log.old<br />
530 mv error_log error_log.old<br />
531 apachectl graceful<br />
533 gzip access_log.old error_log.old
536 <p>Another way to perform log rotation is using <a href="#piped">piped logs</a> as discussed in the next
538 </div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
539 <div class="section">
540 <h2><a name="piped" id="piped">Piped Logs</a></h2>
543 <p>Apache httpd is capable of writing error and access log
544 files through a pipe to another process, rather than directly
545 to a file. This capability dramatically increases the
546 flexibility of logging, without adding code to the main server.
547 In order to write logs to a pipe, simply replace the filename
548 with the pipe character "<code>|</code>", followed by the name
549 of the executable which should accept log entries on its
550 standard input. The server will start the piped-log process when
551 the server starts, and will restart it if it crashes while the
552 server is running. (This last feature is why we can refer to
553 this technique as "reliable piped logging".)</p>
555 <p>Piped log processes are spawned by the parent Apache httpd
556 process, and inherit the userid of that process. This means
557 that piped log programs usually run as root. It is therefore
558 very important to keep the programs simple and secure.</p>
560 <p>One important use of piped logs is to allow log rotation
561 without having to restart the server. The Apache HTTP Server
562 includes a simple program called <code class="program"><a href="./programs/rotatelogs.html">rotatelogs</a></code>
563 for this purpose. For example, to rotate the logs every 24 hours, you
566 <pre class="prettyprint lang-config">
567 CustomLog "|/usr/local/apache/bin/rotatelogs /var/log/access_log 86400" common
571 <p>Notice that quotes are used to enclose the entire command
572 that will be called for the pipe. Although these examples are
573 for the access log, the same technique can be used for the
576 <p>A similar but much more flexible log rotation program
577 called <a href="http://www.cronolog.org/">cronolog</a>
578 is available at an external site.</p>
580 <p>As with conditional logging, piped logs are a very powerful
581 tool, but they should not be used where a simpler solution like
582 off-line post-processing is available.</p>
584 <p>By default the piped log process is spawned without invoking
585 a shell. Use "<code>|$</code>" instead of "<code>|</code>"
586 to spawn using a shell (usually with <code>/bin/sh -c</code>):</p>
588 <pre class="prettyprint lang-config">
589 # Invoke "rotatelogs" using a shell
590 CustomLog "|$/usr/local/apache/bin/rotatelogs /var/log/access_log 86400" common
594 <p>This was the default behaviour for Apache 2.2.
595 Depending on the shell specifics this might lead to
596 an additional shell process for the lifetime of the logging
597 pipe program and signal handling problems during restart.
598 For compatibility reasons with Apache 2.2 the notation
599 "<code>||</code>" is also supported and equivalent to using
600 "<code>|</code>".</p>
601 </div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
602 <div class="section">
603 <h2><a name="virtualhost" id="virtualhost">Virtual Hosts</a></h2>
606 <p>When running a server with many <a href="vhosts/">virtual
607 hosts</a>, there are several options for dealing with log
608 files. First, it is possible to use logs exactly as in a
609 single-host server. Simply by placing the logging directives
610 outside the <code class="directive"><a href="./mod/core.html#virtualhost"><VirtualHost></a></code> sections in the
611 main server context, it is possible to log all requests in the
612 same access log and error log. This technique does not allow
613 for easy collection of statistics on individual virtual
616 <p>If <code class="directive"><a href="./mod/mod_log_config.html#customlog">CustomLog</a></code>
617 or <code class="directive"><a href="./mod/core.html#errorlog">ErrorLog</a></code>
618 directives are placed inside a
619 <code class="directive"><a href="./mod/core.html#virtualhost"><VirtualHost></a></code>
620 section, all requests or errors for that virtual host will be
621 logged only to the specified file. Any virtual host which does
622 not have logging directives will still have its requests sent
623 to the main server logs. This technique is very useful for a
624 small number of virtual hosts, but if the number of hosts is
625 very large, it can be complicated to manage. In addition, it
626 can often create problems with <a href="vhosts/fd-limits.html">insufficient file
629 <p>For the access log, there is a very good compromise. By
630 adding information on the virtual host to the log format
631 string, it is possible to log all hosts to the same log, and
632 later split the log into individual files. For example,
633 consider the following directives.</p>
635 <pre class="prettyprint lang-config">
636 LogFormat "%v %l %u %t \"%r\" %>s %b" comonvhost
637 CustomLog logs/access_log comonvhost
641 <p>The <code>%v</code> is used to log the name of the virtual
642 host that is serving the request. Then a program like <a href="programs/other.html">split-logfile</a> can be used to
643 post-process the access log in order to split it into one file
644 per virtual host.</p>
645 </div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
646 <div class="section">
647 <h2><a name="other" id="other">Other Log Files</a></h2>
650 <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>
652 <h3>Logging actual bytes sent and received</h3>
655 <p><code class="module"><a href="./mod/mod_logio.html">mod_logio</a></code> adds in two additional
656 <code class="directive"><a href="./mod/mod_log_config.html#logformat">LogFormat</a></code> fields
657 (%I and %O) that log the actual number of bytes received and sent
661 <h3>Forensic Logging</h3>
664 <p><code class="module"><a href="./mod/mod_log_forensic.html">mod_log_forensic</a></code> provides for forensic logging of
665 client requests. Logging is done before and after processing a
666 request, so the forensic log contains two log lines for each
667 request. The forensic logger is very strict with no customizations.
668 It can be an invaluable debugging and security tool.</p>
671 <h3><a name="pidfile" id="pidfile">PID File</a></h3>
674 <p>On startup, Apache httpd saves the process id of the parent
675 httpd process to the file <code>logs/httpd.pid</code>. This
676 filename can be changed with the <code class="directive"><a href="./mod/mpm_common.html#pidfile">PidFile</a></code> directive. The
677 process-id is for use by the administrator in restarting and
678 terminating the daemon by sending signals to the parent
679 process; on Windows, use the -k command line option instead.
680 For more information see the <a href="stopping.html">Stopping
681 and Restarting</a> page.</p>
684 <h3><a name="scriptlog" id="scriptlog">Script Log</a></h3>
687 <p>In order to aid in debugging, the
688 <code class="directive"><a href="./mod/mod_cgi.html#scriptlog">ScriptLog</a></code> directive
689 allows you to record the input to and output from CGI scripts.
690 This should only be used in testing - not for live servers.
691 More information is available in the <a href="mod/mod_cgi.html">mod_cgi</a> documentation.</p>
695 <div class="bottomlang">
696 <p><span>Available Languages: </span><a href="./en/logs.html" title="English"> en </a> |
697 <a href="./fr/logs.html" hreflang="fr" rel="alternate" title="Français"> fr </a> |
698 <a href="./ja/logs.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a> |
699 <a href="./ko/logs.html" hreflang="ko" rel="alternate" title="Korean"> ko </a> |
700 <a href="./tr/logs.html" hreflang="tr" rel="alternate" title="Türkçe"> tr </a></p>
701 </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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