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10 <title>mod_lbmethod_bybusyness - Apache HTTP Server Version 2.5</title>
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27 <div id="preamble"><h1>Apache Module mod_lbmethod_bybusyness</h1>
29 <p><span>Available Languages: </span><a href="../en/mod/mod_lbmethod_bybusyness.html" title="English"> en </a> |
30 <a href="../fr/mod/mod_lbmethod_bybusyness.html" hreflang="fr" rel="alternate" title="Français"> fr </a></p>
32 <table class="module"><tr><th><a href="module-dict.html#Description">Description:</a></th><td>Pending Request Counting load balancer scheduler algorithm for <code class="module"><a href="../mod/mod_proxy_balancer.html">mod_proxy_balancer</a></code></td></tr>
33 <tr><th><a href="module-dict.html#Status">Status:</a></th><td>Extension</td></tr>
34 <tr><th><a href="module-dict.html#ModuleIdentifier">Module Identifier:</a></th><td>lbmethod_bybusyness_module</td></tr>
35 <tr><th><a href="module-dict.html#SourceFile">Source File:</a></th><td>mod_lbmethod_bybusyness.c</td></tr>
36 <tr><th><a href="module-dict.html#Compatibility">Compatibility:</a></th><td>Split off from <code class="module"><a href="../mod/mod_proxy_balancer.html">mod_proxy_balancer</a></code> in 2.3</td></tr></table>
39 <p>This module does not provide any configuration directives of its own.
40 It requires the services of <code class="module"><a href="../mod/mod_proxy_balancer.html">mod_proxy_balancer</a></code>, and
41 provides the <code>bybusyness</code> load balancing method.</p>
43 <div id="quickview"><h3>Topics</h3>
45 <li><img alt="" src="../images/down.gif" /> <a href="#busyness">Pending Request Counting Algorithm</a></li>
46 </ul><h3 class="directives">Directives</h3>
47 <p>This module provides no
49 <h3>Bugfix checklist</h3><ul class="seealso"><li><a href="https://www.apache.org/dist/httpd/CHANGES_2.4">httpd changelog</a></li><li><a href="https://bz.apache.org/bugzilla/buglist.cgi?bug_status=__open__&list_id=144532&product=Apache%20httpd-2&query_format=specific&order=changeddate%20DESC%2Cpriority%2Cbug_severity&component=mod_lbmethod_bybusyness">Known issues</a></li><li><a href="https://bz.apache.org/bugzilla/enter_bug.cgi?product=Apache%20httpd-2&component=mod_lbmethod_bybusyness">Report a bug</a></li></ul><h3>See also</h3>
51 <li><code class="module"><a href="../mod/mod_proxy.html">mod_proxy</a></code></li>
52 <li><code class="module"><a href="../mod/mod_proxy_balancer.html">mod_proxy_balancer</a></code></li>
53 <li><a href="#comments_section">Comments</a></li></ul></div>
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56 <h2><a name="busyness" id="busyness">Pending Request Counting Algorithm</a><a title="Permanent link" href="#busyness" class="permalink">¶</a></h2>
60 <p>Enabled via <code>lbmethod=bybusyness</code>, this scheduler keeps
61 track of how many requests each worker is currently assigned at present. A new
62 request is automatically assigned to the worker with the lowest
63 number of active requests. This is useful in the case of workers
64 that queue incoming requests independently of Apache, to ensure that
65 queue length stays even and a request is always given to the worker
66 most likely to service it the fastest and reduce latency.</p>
68 <p>In the case of multiple least-busy workers, the statistics (and
69 weightings) used by the Request Counting method are used to break the
70 tie. Over time, the distribution of work will come to resemble that
71 characteristic of <code>byrequests</code> (as implemented
72 by <code class="module"><a href="../mod/mod_lbmethod_byrequests.html">mod_lbmethod_byrequests</a></code>).</p>
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