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109a53dbf4c9233f869f63ba7a7f3fece49973c3Christian Maeder<div id="page-content">
109a53dbf4c9233f869f63ba7a7f3fece49973c3Christian Maeder<div id="preamble"><h1>Apache Module mod_lbmethod_bybusyness</h1>
4811c997e10bcfbd8e0fdfb130c3368abd33bbcaEugen Kuksa<div class="toplang">
bbba10ee00dcf6bcbc9f22473b1acd0983b10512notanartist<p><span>Available Languages: </span><a href="/en/mod/mod_lbmethod_bybusyness.html" title="English">&nbsp;en&nbsp;</a></p>
df87ff823273ae2969e9d29e833845b4c0a9ee77notanartist</div>
109a53dbf4c9233f869f63ba7a7f3fece49973c3Christian Maeder<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>
109a53dbf4c9233f869f63ba7a7f3fece49973c3Christian Maeder<tr><th><a href="module-dict.html#Status">Status:</a></th><td>Extension</td></tr>
ea5ccb1c6e89486a54e1f4bd95840147e96093edChristian Maeder<tr><th><a href="module-dict.html#ModuleIdentifier">Module�Identifier:</a></th><td>lbmethod_bybusyness_module</td></tr>
109a53dbf4c9233f869f63ba7a7f3fece49973c3Christian Maeder<tr><th><a href="module-dict.html#SourceFile">Source�File:</a></th><td>mod_lbmethod_bybusyness.c</td></tr>
109a53dbf4c9233f869f63ba7a7f3fece49973c3Christian Maeder<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>
85e1d54a475bfc30b3eac5ae6c5e42a2d7e93f10Christian Maeder<h3>Summary</h3>
85e1d54a475bfc30b3eac5ae6c5e42a2d7e93f10Christian Maeder
109a53dbf4c9233f869f63ba7a7f3fece49973c3Christian Maeder<p>This module does not provide any configuration directives of its own.
fe495a0978e5aa70776103c37fb0eb2bd6abea69Eugen KuksaIt requires the services of <code class="module"><a href="/mod/mod_proxy_balancer.html">mod_proxy_balancer</a></code>, and
91e24fc45834b35f2a3830d72565640251149bf3Christian Maederprovides the <code>bybusyness</code> load balancing method.</p>
109a53dbf4c9233f869f63ba7a7f3fece49973c3Christian Maeder</div>
109a53dbf4c9233f869f63ba7a7f3fece49973c3Christian Maeder<div id="quickview"><h3>Topics</h3>
109a53dbf4c9233f869f63ba7a7f3fece49973c3Christian Maeder<ul id="topics">
109a53dbf4c9233f869f63ba7a7f3fece49973c3Christian Maeder<li><img alt="" src="/images/down.gif" /> <a href="#busyness">Pending Request Counting Algorithm</a></li>
109a53dbf4c9233f869f63ba7a7f3fece49973c3Christian Maeder</ul><h3 class="directives">Directives</h3>
109a53dbf4c9233f869f63ba7a7f3fece49973c3Christian Maeder<p>This module provides no
109a53dbf4c9233f869f63ba7a7f3fece49973c3Christian Maeder directives.</p>
0130083f314580170af1195037be3325f125fbceChristian Maeder<h3>See also</h3>
109a53dbf4c9233f869f63ba7a7f3fece49973c3Christian Maeder<ul class="seealso">
0130083f314580170af1195037be3325f125fbceChristian Maeder<li><code class="module"><a href="/mod/mod_proxy.html">mod_proxy</a></code></li>
109a53dbf4c9233f869f63ba7a7f3fece49973c3Christian Maeder<li><code class="module"><a href="/mod/mod_proxy_balancer.html">mod_proxy_balancer</a></code></li>
109a53dbf4c9233f869f63ba7a7f3fece49973c3Christian Maeder</ul><ul class="seealso"><li><a href="#comments_section">Comments</a></li></ul></div>
109a53dbf4c9233f869f63ba7a7f3fece49973c3Christian Maeder<div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div>
109a53dbf4c9233f869f63ba7a7f3fece49973c3Christian Maeder<div class="section">
109a53dbf4c9233f869f63ba7a7f3fece49973c3Christian Maeder<h2><a name="busyness" id="busyness">Pending Request Counting Algorithm</a></h2>
109a53dbf4c9233f869f63ba7a7f3fece49973c3Christian Maeder
bbba6dd86153aacb0f662b182b128df0eb09fd54Christian Maeder
109a53dbf4c9233f869f63ba7a7f3fece49973c3Christian Maeder
a461314c811f4187dff85c8be079a41b2f13f176Christian Maeder <p>Enabled via <code>lbmethod=bybusyness</code>, this scheduler keeps
4eb859461f8fd904f40f57261cf23e5c73cf8ecaChristian Maeder track of how many requests each worker is currently assigned at present. A new
a31430de8b0632d29f42634d6395e982bf31b14dChristian Maeder request is automatically assigned to the worker with the lowest
109a53dbf4c9233f869f63ba7a7f3fece49973c3Christian Maeder number of active requests. This is useful in the case of workers
b53688bfed888214b485cf76439d57262d80e0a7Christian Maeder that queue incoming requests independently of Apache, to ensure that
b53688bfed888214b485cf76439d57262d80e0a7Christian Maeder queue length stays even and a request is always given to the worker
be43c3fa0292555bd126784ae27ff5c1d23438cbChristian Maeder most likely to service it the fastest and reduce latency.</p>
a389e88e0acb83d8489bdc5e55bc5522b152bbecEugen Kuksa
a389e88e0acb83d8489bdc5e55bc5522b152bbecEugen Kuksa <p>In the case of multiple least-busy workers, the statistics (and
a389e88e0acb83d8489bdc5e55bc5522b152bbecEugen Kuksa weightings) used by the Request Counting method are used to break the
b53688bfed888214b485cf76439d57262d80e0a7Christian Maeder tie. Over time, the distribution of work will come to resemble that
16b71dad8d398af412d66a4f4763f1ada5b03d23Christian Maeder characteristic of <code>byrequests</code> (as implemented
f39b8dd9651dfcc38b06191cda23cacbfc298323Christian Maeder by <code class="module"><a href="/mod/mod_lbmethod_byrequests.html">mod_lbmethod_byrequests</a></code>).</p>
b53688bfed888214b485cf76439d57262d80e0a7Christian Maeder
7f7460e7095628f3437b116ee78d3043d11f8febChristian Maeder</div>
3a9d784341454573b50b32fa1b494e7418df3086Christian Maeder</div>
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b53688bfed888214b485cf76439d57262d80e0a7Christian Maeder<p><span>Available Languages: </span><a href="/en/mod/mod_lbmethod_bybusyness.html" title="English">&nbsp;en&nbsp;</a></p>
b53688bfed888214b485cf76439d57262d80e0a7Christian Maeder</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&amp;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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