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| author | Takashi Sato <takashi@apache.org> | 2008-12-06 17:09:42 +0000 |
|---|---|---|
| committer | Takashi Sato <takashi@apache.org> | 2008-12-06 17:09:42 +0000 |
| commit | 746e3a6e1fef203a225ea0c912ae6acf457ad134 (patch) | |
| tree | 30b981eb33aefeb432e6e91018940fd8f2ab4032 /docs/manual/mod/mod_lbmethod_byrequests.html.en | |
| parent | c73a91e509adf2b58ef9b13763dc6ac8338a4e53 (diff) | |
| download | httpd-746e3a6e1fef203a225ea0c912ae6acf457ad134.tar.gz | |
update transformations
git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@724013 13f79535-47bb-0310-9956-ffa450edef68
Diffstat (limited to 'docs/manual/mod/mod_lbmethod_byrequests.html.en')
| -rw-r--r-- | docs/manual/mod/mod_lbmethod_byrequests.html.en | 224 |
1 files changed, 224 insertions, 0 deletions
diff --git a/docs/manual/mod/mod_lbmethod_byrequests.html.en b/docs/manual/mod/mod_lbmethod_byrequests.html.en new file mode 100644 index 0000000000..7bc07addd2 --- /dev/null +++ b/docs/manual/mod/mod_lbmethod_byrequests.html.en @@ -0,0 +1,224 @@ +<?xml version="1.0" encoding="ISO-8859-1"?> +<!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><!-- + XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX + This file is generated from xml source: DO NOT EDIT + XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX + --> +<title>mod_lbmethod_byrequests - Apache HTTP Server</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 href="../images/favicon.ico" rel="shortcut icon" /></head> +<body> +<div id="page-header"> +<p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/directives.html">Directives</a> | <a href="../faq/">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p> +<p class="apache">Apache HTTP Server Version 2.3</p> +<img alt="" src="../images/feather.gif" /></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 2.3</a> > <a href="./">Modules</a></div> +<div id="page-content"> +<div id="preamble"><h1>Apache Module mod_lbmethod_byrequests</h1> +<div class="toplang"> +<p><span>Available Languages: </span><a href="../en/mod/mod_lbmethod_byrequests.html" title="English"> en </a></p> +</div> +<table class="module"><tr><th><a href="module-dict.html#Description">Description:</a></th><td>Request Counting load balancer scheduler algorithm for <code class="module"><a href="../mod/mod_proxy_balancer.html">mod_proxy_balancer</a></code></td></tr> +<tr><th><a href="module-dict.html#Status">Status:</a></th><td>Extension</td></tr> +<tr><th><a href="module-dict.html#ModuleIdentifier">Module Identifier:</a></th><td>lbmethod_byrequests_module</td></tr> +<tr><th><a href="module-dict.html#SourceFile">Source File:</a></th><td>mod_lbmethod_byrequests.c</td></tr> +<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> +<h3>Summary</h3> + +</div> +<div id="quickview"><h3 class="directives">Directives</h3> +<p>This module provides no + directives.</p> +<h3>Topics</h3> +<ul id="topics"> +<li><img alt="" src="../images/down.gif" /> <a href="#requests">Request Counting Algorithm</a></li> +</ul><h3>See also</h3> +<ul class="seealso"> +<li><code class="module"><a href="../mod/mod_proxy.html">mod_proxy</a></code></li> +<li><code class="module"><a href="../mod/mod_proxy_balancer.html">mod_proxy_balancer</a></code></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="requests" id="requests">Request Counting Algorithm</a></h2> + + <p>Enabled via <code>lbmethod=byrequests</code>, the idea behind this + scheduler is that we distribute the requests among the + various workers to ensure that each gets their configured share + of the number of requests. It works as follows:</p> + + <p><dfn>lbfactor</dfn> is <em>how much we expect this worker + to work</em>, or <em>the workers's work quota</em>. This is + a normalized value representing their "share" of the amount of + work to be done.</p> + + <p><dfn>lbstatus</dfn> is <em>how urgent this worker has to work + to fulfill its quota of work</em>.</p> + + <p>The <dfn>worker</dfn> is a member of the load balancer, + usually a remote host serving one of the supported protocols.</p> + + <p>We distribute each worker's work quota to the worker, and then look + which of them needs to work most urgently (biggest lbstatus). This + worker is then selected for work, and its lbstatus reduced by the + total work quota we distributed to all workers. Thus the sum of all + lbstatus does not change(*) and we distribute the requests + as desired.</p> + + <p>If some workers are disabled, the others will + still be scheduled correctly.</p> + + <div class="example"><pre><code>for each worker in workers + worker lbstatus += worker lbfactor + total factor += worker lbfactor + if worker lbstatus > candidate lbstatus + candidate = worker + +candidate lbstatus -= total factor</code></pre></div> + + <p>If a balancer is configured as follows:</p> + + <table><tr><th>worker</th> + <th class="data">a</th> + <th class="data">b</th> + <th class="data">c</th> + <th class="data">d</th></tr> +<tr><th>lbfactor</th> + <td class="data">25</td> + <td class="data">25</td> + <td class="data">25</td> + <td class="data">25</td></tr> +<tr><th>lbstatus</th> + <td class="data">0</td> + <td class="data">0</td> + <td class="data">0</td> + <td class="data">0</td></tr> +</table> + + <p>And <var>b</var> gets disabled, the following schedule is produced:</p> + + <table><tr><th>worker</th> + <th class="data">a</th> + <th class="data">b</th> + <th class="data">c</th> + <th class="data">d</th></tr> +<tr><th>lbstatus</th> + <td class="data"><em>-50</em></td> + <td class="data">0</td> + <td class="data">25</td> + <td class="data">25</td></tr> +<tr><th>lbstatus</th> + <td class="data">-25</td> + <td class="data">0</td> + <td class="data"><em>-25</em></td> + <td class="data">50</td></tr> +<tr><th>lbstatus</th> + <td class="data">0</td> + <td class="data">0</td> + <td class="data">0</td> + <td class="data"><em>0</em></td></tr> +<tr><td class="data" colspan="5">(repeat)</td></tr> +</table> + + <p>That is it schedules: <var>a</var> <var>c</var> <var>d</var> + <var>a</var> <var>c</var> <var>d</var> <var>a</var> <var>c</var> + <var>d</var> ... Please note that:</p> + + <table><tr><th>worker</th> + <th class="data">a</th> + <th class="data">b</th> + <th class="data">c</th> + <th class="data">d</th></tr> +<tr><th>lbfactor</th> + <td class="data">25</td> + <td class="data">25</td> + <td class="data">25</td> + <td class="data">25</td></tr> +</table> + + <p>Has the exact same behavior as:</p> + + <table><tr><th>worker</th> + <th class="data">a</th> + <th class="data">b</th> + <th class="data">c</th> + <th class="data">d</th></tr> +<tr><th>lbfactor</th> + <td class="data">1</td> + <td class="data">1</td> + <td class="data">1</td> + <td class="data">1</td></tr> +</table> + + <p>This is because all values of <dfn>lbfactor</dfn> are normalized + with respect to the others. For:</p> + + <table><tr><th>worker</th> + <th class="data">a</th> + <th class="data">b</th> + <th class="data">c</th></tr> +<tr><th>lbfactor</th> + <td class="data">1</td> + <td class="data">4</td> + <td class="data">1</td></tr> +</table> + + <p>worker <var>b</var> will, on average, get 4 times the requests + that <var>a</var> and <var>c</var> will.</p> + + <p>The following asymmetric configuration works as one would expect:</p> + + <table><tr><th>worker</th> + <th class="data">a</th> + <th class="data">b</th></tr> +<tr><th>lbfactor</th> + <td class="data">70</td> + <td class="data">30</td></tr> +<tr><td class="data" colspan="2"> </td></tr> +<tr><th>lbstatus</th> + <td class="data"><em>-30</em></td> + <td class="data">30</td></tr> +<tr><th>lbstatus</th> + <td class="data">40</td> + <td class="data"><em>-40</em></td></tr> +<tr><th>lbstatus</th> + <td class="data"><em>10</em></td> + <td class="data">-10</td></tr> +<tr><th>lbstatus</th> + <td class="data"><em>-20</em></td> + <td class="data">20</td></tr> +<tr><th>lbstatus</th> + <td class="data"><em>-50</em></td> + <td class="data">50</td></tr> +<tr><th>lbstatus</th> + <td class="data">20</td> + <td class="data"><em>-20</em></td></tr> +<tr><th>lbstatus</th> + <td class="data"><em>-10</em></td> + <td class="data">10</td></tr> +<tr><th>lbstatus</th> + <td class="data"><em>-40</em></td> + <td class="data">40</td></tr> +<tr><th>lbstatus</th> + <td class="data">30</td> + <td class="data"><em>-30</em></td></tr> +<tr><th>lbstatus</th> + <td class="data"><em>0</em></td> + <td class="data">0</td></tr> +<tr><td class="data" colspan="3">(repeat)</td></tr> +</table> + + <p>That is after 10 schedules, the schedule repeats and 7 <var>a</var> + are selected with 3 <var>b</var> interspersed.</p> +</div> +</div> +<div class="bottomlang"> +<p><span>Available Languages: </span><a href="../en/mod/mod_lbmethod_byrequests.html" title="English"> en </a></p> +</div><div id="footer"> +<p class="apache">Copyright 2008 The Apache Software Foundation.<br />Licensed under the <a href="http://www.apache.org/licenses/LICENSE-2.0">Apache License, Version 2.0</a>.</p> +<p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/directives.html">Directives</a> | <a href="../faq/">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p></div> +</body></html>
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