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18<p class="apache">Apache HTTP Server Version 2.4</p>
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22<a href="http://www.apache.org/">Apache</a> &gt; <a href="http://httpd.apache.org/">HTTP Server</a> &gt; <a href="http://httpd.apache.org/docs/">Documentation</a> &gt; <a href="../">Version 2.4</a> &gt; <a href="./">Virtual Hosts</a></div><div id="page-content"><div id="preamble"><h1>File Descriptor Limits</h1>
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31
32    <p>When using a large number of Virtual Hosts, Apache may run
33    out of available file descriptors (sometimes called <cite>file
34    handles</cite>) if each Virtual Host specifies different log
35    files. The total number of file descriptors used by Apache is
36    one for each distinct error log file, one for every other log
37    file directive, plus 10-20 for internal use. Unix operating
38    systems limit the number of file descriptors that may be used
39    by a process; the limit is typically 64, and may usually be
40    increased up to a large hard-limit.</p>
41
42    <p>Although Apache attempts to increase the limit as required,
43    this may not work if:</p>
44
45    <ol>
46      <li>Your system does not provide the <code>setrlimit()</code>
47      system call.</li>
48
49      <li>The <code>setrlimit(RLIMIT_NOFILE)</code> call does not
50      function on your system (such as Solaris 2.3)</li>
51
52      <li>The number of file descriptors required exceeds the hard
53      limit.</li>
54
55      <li>Your system imposes other limits on file descriptors,
56      such as a limit on stdio streams only using file descriptors
57      below 256. (Solaris 2)</li>
58    </ol>
59
60    <p>In the event of problems you can:</p>
61
62    <ul>
63      <li>Reduce the number of log files; don't specify log files
64      in the <code class="directive"><a href="/mod/core.html#virtualhost">&lt;VirtualHost&gt;</a></code>
65      sections, but only log to the main log files. (See <a href="#splitlogs">Splitting up your log files</a>, below, for more
66      information on doing this.)</li>
67
68      <li>
69        If you system falls into 1 or 2 (above), then increase the
70        file descriptor limit before starting Apache, using a
71        script like
72
73        <div class="example"><p><code>
74          <code>#!/bin/sh<br />
75           ulimit -S -n 100<br />
76           exec httpd</code>
77        </code></p></div>
78      </li>
79    </ul>
80
81</div>
82<div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div>
83<div class="section">
84<h2><a name="splitlogs" id="splitlogs">Splitting up your log files</a></h2>
85
86<p>If you want to log multiple virtual hosts to the same log file, you
87may want to split up the log files afterwards in order to run
88statistical analysis of the various virtual hosts. This can be
89accomplished in the following manner.</p>
90
91<p>First, you will need to add the virtual host information to the log
92entries. This can be done using the <code class="directive"><a href="/mod/mod_log_config.html#logformat">
93LogFormat</a></code>
94directive, and the <code>%v</code> variable. Add this to the beginning
95of your log format string:</p>
96
97<pre class="prettyprint lang-config">LogFormat "%v %h %l %u %t \"%r\" %&gt;s %b" vhost
98CustomLog logs/multiple_vhost_log vhost</pre>
99
100
101<p>This will create a log file in the common log format, but with the
102canonical virtual host (whatever appears in the
103<code class="directive"><a href="/mod/core.html#servername">ServerName</a></code> directive) prepended to
104each line. (See <code class="module"><a href="/mod/mod_log_config.html">mod_log_config</a></code> for
105more about customizing your log files.)</p>
106
107<p>When you wish to split your log file into its component parts (one
108file per virtual host) you can use the program <code><a href="/programs/other.html">split-logfile</a></code> to accomplish
109this. You'll find this program in the <code>support</code> directory
110of the Apache distribution.</p>
111
112<p>Run this program with the command:</p>
113
114<div class="example"><p><code>
115split-logfile &lt; /logs/multiple_vhost_log
116</code></p></div>
117
118<p>This program, when run with the name of your vhost log file, will
119generate one file for each virtual host that appears in your log file.
120Each file will be called <code>hostname.log</code>.</p>
121
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