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| author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-08 19:09:22 +0000 |
|---|---|---|
| committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-08 19:09:22 +0000 |
| commit | 2faa747e2303ee774a4b4aace961188e950e185a (patch) | |
| tree | 604e79c7481956ce48f458e3546eaf1090b3ffff /docs/manual/logs.html.en | |
| parent | Initial commit. (diff) | |
| download | apache2-2faa747e2303ee774a4b4aace961188e950e185a.tar.xz apache2-2faa747e2303ee774a4b4aace961188e950e185a.zip | |
Adding upstream version 2.4.58.upstream/2.4.58
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'docs/manual/logs.html.en')
| -rw-r--r-- | docs/manual/logs.html.en | 710 |
1 files changed, 710 insertions, 0 deletions
diff --git a/docs/manual/logs.html.en b/docs/manual/logs.html.en new file mode 100644 index 0000000..7be8a96 --- /dev/null +++ b/docs/manual/logs.html.en @@ -0,0 +1,710 @@ +<?xml version="1.0" encoding="UTF-8"?> +<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> +<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en"><head> +<meta content="text/html; charset=UTF-8" http-equiv="Content-Type" /> +<!-- + XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX + This file is generated from xml source: DO NOT EDIT + XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX + --> +<title>Log Files - Apache HTTP Server Version 2.4</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 rel="stylesheet" type="text/css" href="./style/css/prettify.css" /> +<script src="./style/scripts/prettify.min.js" type="text/javascript"> +</script> + +<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="http://wiki.apache.org/httpd/FAQ">FAQ</a> | <a href="./glossary.html">Glossary</a> | <a href="./sitemap.html">Sitemap</a></p> +<p class="apache">Apache HTTP Server Version 2.4</p> +<img alt="" src="./images/feather.png" /></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 2.4</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 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"><a href="https://www.apache.org/foundation/contributing.html" class="badge"><img src="https://www.apache.org/images/SupportApache-small.png" alt="Support Apache!" /></a><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><h3>See also</h3><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 + are stored in without being aware of the consequences; see the + <a href="misc/security_tips.html">security tips</a> document + for details.</p> + + <p>In addition, log files may contain information supplied + directly by the client, without escaping. Therefore, it is + 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><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 + will send diagnostic information and record any errors that it + encounters in processing requests. It is the first place to + look when a problem occurs with starting the server or with the + operation of the server, since it will often contain details of + 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 + 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 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> + [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 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 + log will also contain debugging output from CGI scripts. Any + information written to <code>stderr</code> by a CGI script will + be copied directly to the error log.</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 + 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="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 + the contents of the logs. This section describes how to configure the server + to record information in the access log.</p> + + <p>Storing the information in the access log is only + the start of log management. The next step is to analyze this + information to produce useful statistics. Log analysis in + general is beyond the scope of this document, and not really + part of the job of the web server itself. + </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> + + <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> + + <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 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> + + <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 + analysis programs. The log file entries produced in CLF will + look something like this:</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>Each part of this log entry is described below.</p> + + <dl> + <dt><code>127.0.0.1</code> (<code>%h</code>)</dt> + + <dd>This is the IP address of the client (remote host) which + made the request to the server. If <code class="directive"><a href="./mod/core.html#hostnamelookups">HostnameLookups</a></code> is + set to <code>On</code>, then the server will try to determine + 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 <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 + server, this address will be the address of the proxy, rather + than the originating machine.</dd> + + <dt><code>-</code> (<code>%l</code>)</dt> + + <dd>The "hyphen" in the output indicates that the requested + piece of information is not available. In this case, the + information that is not available is the RFC 1413 identity of + the client determined by <code>identd</code> on the clients + 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/mod_ident.html#identitycheck">IdentityCheck</a></code> is set + to <code>On</code>.</dd> + + <dt><code>frank</code> (<code>%u</code>)</dt> + + <dd>This is the userid of the person requesting the document + as determined by HTTP authentication. The same value is + typically provided to CGI scripts in the + <code>REMOTE_USER</code> environment variable. If the status + 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 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 request was received. + The format is: + + <p class="indent"> + <code>[day/month/year:hour:minute:second zone]<br /> + day = 2*digit<br /> + month = 3*letter<br /> + year = 4*digit<br /> + hour = 2*digit<br /> + minute = 2*digit<br /> + second = 2*digit<br /> + zone = (`+' | `-') 4*digit</code> + </p> + <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 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> + (<code>\"%r\"</code>)</dt> + + <dd>The request line from the client is given in double + quotes. The request line contains a great deal of useful + information. First, the method used by the client is + <code>GET</code>. Second, the client requested the resource + <code>/apache_pb.gif</code>, and third, the client used the + protocol <code>HTTP/1.0</code>. It is also possible to log + one or more parts of the request line independently. For + example, the format string "<code>%m %U%q %H</code>" will log + the method, path, query-string, and protocol, resulting in + exactly the same output as "<code>%r</code>".</dd> + + <dt><code>200</code> (<code>%>s</code>)</dt> + + <dd>This is the status code that the server sends back to the + client. This information is very valuable, because it reveals + whether the request resulted in a successful response (codes + beginning in 2), a redirection (codes beginning in 3), an + error caused by the client (codes beginning in 4), or an + error in the server (codes beginning in 5). The full list of + possible status codes can be found in the <a href="http://www.w3.org/Protocols/rfc2616/rfc2616.txt">HTTP + specification</a> (RFC2616 section 10).</dd> + + <dt><code>2326</code> (<code>%b</code>)</dt> + + <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> + + <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 + fields uses the percent-directive + <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 + "http://www.example.com/start.html" "Mozilla/4.08 [en] + (Win98; I ;Nav)" + </code></p></div> + + <p>The additional fields are:</p> + + <dl> + <dt><code>"http://www.example.com/start.html"</code> + (<code>\"%{Referer}i\"</code>)</dt> + + <dd>The "Referer" (sic) HTTP request header. This gives the + site that the client reports having been referred from. (This + should be the page that links to or includes + <code>/apache_pb.gif</code>).</dd> + + <dt><code>"Mozilla/4.08 [en] (Win98; I ;Nav)"</code> + (<code>\"%{User-agent}i\"</code>)</dt> + + <dd>The User-Agent HTTP request header. This is the + identifying information that the client browser reports about + 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> + directives in the configuration + file. For example, the following directives will create three + access logs. The first contains the basic CLF information, + while the second and third contain referer and browser + 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> + + <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 + <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> + + <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> + + + <p>As another example, consider logging requests from + english-speakers to one log file, and non-english speakers to a + different log file.</p> + + <pre class="prettyprint lang-config">SetEnvIf Accept-Language "en" english +CustomLog logs/english_log common env=english +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, 304, or 302. (Note the + "!" before the status codes.</p> + + <p>Although we have just shown that conditional logging is very + 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> + + + <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 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>By using a <em>graceful</em> restart, the server can be + instructed to open new log files without losing any existing or + pending connections from clients. However, in order to + accomplish this, the server must continue to write to the old + log files while it finishes serving old requests. It is + therefore necessary to wait for some time after the restart + before doing any processing on the log files. A typical + scenario that simply rotates the logs and compresses the old + logs to save space is:</p> + + <div class="example"><p><code> + mv access_log access_log.old<br /> + mv error_log error_log.old<br /> + apachectl graceful<br /> + sleep 600<br /> + gzip access_log.old error_log.old + </code></p></div> + + <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> + + + <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 + flexibility of logging, without adding code to the main server. + 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. 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>Piped log processes are spawned by the parent Apache httpd + process, and inherit the userid of that process. This means + that piped log programs usually run as root. It is therefore + very important to keep the programs simple and secure.</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 <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> + + <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>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> + + <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 class="note"><h3>Windows note</h3> + <p>Note that on Windows, you may run into problems when running many piped + logger processes, especially when HTTPD is running as a service. This is + caused by running out of desktop heap space. The desktop heap space given + to each service is specified by the third argument to the + <code>SharedSection</code> parameter in the + HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\SessionManager\SubSystems\Windows + registry value. <strong>Change this value with care</strong>; the normal + caveats for changing the Windows registry apply, but you might also exhaust + the desktop heap pool if the number is adjusted too high.</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="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 + single-host server. Simply by placing the logging directives + outside the <code class="directive"><a href="./mod/core.html#virtualhost"><VirtualHost></a></code> sections in the + main server context, it is possible to log all requests in the + same access log and error log. This technique does not allow + 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> + 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> + section, all requests or errors for that virtual host will be + logged only to the specified file. Any virtual host which does + not have logging directives will still have its requests sent + to the main server logs. This technique is very useful for a + small number of virtual hosts, but if the number of hosts is + very large, it can be complicated to manage. In addition, it + can often create problems with <a href="vhosts/fd-limits.html">insufficient file + descriptors</a>.</p> + + <p>For the access log, there is a very good compromise. By + adding information on the virtual host to the log format + string, it is possible to log all hosts to the same log, and + later split the log into individual files. For example, + consider the following directives.</p> + + <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/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> + + + <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> + + + <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 + process-id is for use by the administrator in restarting and + 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> + + + <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> + + + </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. 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