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234 lines
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<?xml version="1.0" encoding="ISO-8859-1"?>
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en"><head><!--
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XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
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This file is generated from xml source: DO NOT EDIT
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-->
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<title>mod_proxy_balancer - Apache HTTP Server</title>
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<link href="../style/css/manual.css" rel="stylesheet" media="all" type="text/css" title="Main stylesheet" />
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<link href="../style/css/manual-loose-100pc.css" rel="alternate stylesheet" media="all" type="text/css" title="No Sidebar - Default font size" />
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<link href="../style/css/manual-print.css" rel="stylesheet" media="print" type="text/css" />
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<link href="../images/favicon.ico" rel="shortcut icon" /></head>
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<body>
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<div id="page-header">
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<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>
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<p class="apache">Apache HTTP Server Version 2.3</p>
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<img alt="" src="../images/feather.gif" /></div>
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<div class="up"><a href="./"><img title="<-" alt="<-" src="../images/left.gif" /></a></div>
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<div id="path">
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<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>
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<div id="page-content">
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<div id="preamble"><h1>Apache Module mod_proxy_balancer</h1>
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<div class="toplang">
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<p><span>Available Languages: </span><a href="../en/mod/mod_proxy_balancer.html" title="English"> en </a> |
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<a href="../ja/mod/mod_proxy_balancer.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a></p>
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</div>
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<table class="module"><tr><th><a href="module-dict.html#Description">Description:</a></th><td><code class="module"><a href="../mod/mod_proxy.html">mod_proxy</a></code> extension for load balancing </td></tr>
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<tr><th><a href="module-dict.html#Status">Status:</a></th><td>Extension</td></tr>
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<tr><th><a href="module-dict.html#ModuleIdentifier">Module<EFBFBD>Identifier:</a></th><td>proxy_balancer_module</td></tr>
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<tr><th><a href="module-dict.html#SourceFile">Source<EFBFBD>File:</a></th><td>mod_proxy_balancer.c</td></tr>
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<tr><th><a href="module-dict.html#Compatibility">Compatibility:</a></th><td>Available in version 2.1 and later</td></tr></table>
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<h3>Summary</h3>
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<p>This module <em>requires</em> the service of <code class="module"><a href="../mod/mod_proxy.html">mod_proxy</a></code>. It provides load balancing support for
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<code>HTTP</code>, <code>FTP</code> and <code>AJP13</code> protocols
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</p>
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<p>Load balancing scheduler algorithm is provided by not this
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module but other modules such as:
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<code class="module"><a href="../mod/mod_lbmethod_byrequests.html">mod_lbmethod_byrequests</a></code>,
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<code class="module"><a href="../mod/mod_lbmethod_bytraffic.html">mod_lbmethod_bytraffic</a></code> and
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<code class="module"><a href="../mod/mod_lbmethod_bybusyness.html">mod_lbmethod_bybusyness</a></code>.
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</p>
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<p>Thus, in order to get the ability of load balancing,
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<code class="module"><a href="../mod/mod_proxy.html">mod_proxy</a></code>, <code class="module"><a href="../mod/mod_proxy_balancer.html">mod_proxy_balancer</a></code>
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and at least one of load balancing scheduler algorithm modules have
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to be present in the server.</p>
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<div class="warning"><h3>Warning</h3>
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<p>Do not enable proxying until you have <a href="mod_proxy.html#access">secured your server</a>. Open proxy
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servers are dangerous both to your network and to the Internet at
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large.</p>
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</div>
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</div>
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<div id="quickview"><h3 class="directives">Directives</h3>
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<ul id="toc">
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<li><img alt="" src="../images/down.gif" /> <a href="#balancernonce">BalancerNonce</a></li>
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</ul>
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<h3>Topics</h3>
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<ul id="topics">
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<li><img alt="" src="../images/down.gif" /> <a href="#scheduler">Load balancer scheduler algorithm</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#example">Examples of a balancer configuration</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#environment">Exported Environment Variables</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#enable">Enabling Balancer Manager Support</a></li>
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</ul><h3>See also</h3>
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<ul class="seealso">
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<li><code class="module"><a href="../mod/mod_proxy.html">mod_proxy</a></code></li>
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</ul></div>
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<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
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<div class="section">
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<h2><a name="scheduler" id="scheduler">Load balancer scheduler algorithm</a></h2>
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<p>At present, there are 3 load balancer scheduler algorithms available
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for use: Request Counting, Weighted Traffic Counting and Pending Request
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Counting. These are controlled via the <code>lbmethod</code> value of
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the Balancer definition. See the <code class="directive"><a href="../mod/mod_proxy.html#proxypass">ProxyPass</a></code>
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directive for more information.</p>
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</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
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<div class="section">
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<h2><a name="example" id="example">Examples of a balancer configuration</a></h2>
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<p>Before we dive into the technical details, here's an example of
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how you might use <code class="module"><a href="../mod/mod_proxy_balancer.html">mod_proxy_balancer</a></code> to provide
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load balancing between two back-end servers:
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</p>
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<div class="example"><p><code>
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<Proxy balancer://mycluster><br />
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BalancerMember http://192.168.1.50:80<br />
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BalancerMember http://192.168.1.51:80<br />
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</Proxy><br />
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ProxyPass /test balancer://mycluster
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</code></p></div>
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<p>Another example of how to provide load balancing with stickyness
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using <code class="module"><a href="../mod/mod_headers.html">mod_headers</a></code>, even if the backend server does
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not set a suitable session cookie:
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</p>
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<div class="example"><p><code>
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Header add Set-Cookie: "ROUTEID=.%{BALANCER_WORKER_ROUTE}e; path=/"
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env=BALANCER_ROUTE_CHANGED<br />
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<Proxy balancer://mycluster><br />
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BalancerMember http://192.168.1.50:80 route=1<br />
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BalancerMember http://192.168.1.51:80 route=2<br />
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ProxySet stickysession=ROUTEID<br />
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</Proxy><br />
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ProxyPass /test balancer://mycluster
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</code></p></div>
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</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
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<div class="section">
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<h2><a name="environment" id="environment">Exported Environment Variables</a></h2>
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<p>At present there are 6 environment variables exported:</p>
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<dl>
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<dt><var><a name="balancer_session_sticky" id="balancer_session_sticky">BALANCER_SESSION_STICKY</a></var></dt>
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<dd>
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<p>This is assigned the <var>stickysession</var> value used in the current
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request. It is the cookie or parameter name used for sticky sessions</p>
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</dd>
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<dt><var><a name="balancer_session_route" id="balancer_session_route">BALANCER_SESSION_ROUTE</a></var></dt>
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<dd>
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<p>This is assigned the <var>route</var> parsed from the current
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request.</p>
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</dd>
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<dt><var><a name="balancer_name" id="balancer_name">BALANCER_NAME</a></var></dt>
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<dd>
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<p>This is assigned the name of the balancer used for the current
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request. The value is something like <code>balancer://foo</code>.</p>
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</dd>
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<dt><var><a name="balancer_worker_name" id="balancer_worker_name">BALANCER_WORKER_NAME</a></var></dt>
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<dd>
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<p>This is assigned the name of the worker used for the current request.
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The value is something like <code>http://hostA:1234</code>.</p>
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</dd>
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<dt><var><a name="balancer_worker_route" id="balancer_worker_route">BALANCER_WORKER_ROUTE</a></var></dt>
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<dd>
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<p>This is assigned the <var>route</var> of the worker that will be
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used for the current request.</p>
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</dd>
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<dt><var><a name="balancer_route_changed" id="balancer_route_changed">BALANCER_ROUTE_CHANGED</a></var></dt>
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<dd>
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<p>This is set to 1 if the session route does not match the
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worker route (BALANCER_SESSION_ROUTE != BALANCER_WORKER_ROUTE) or the
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session does not yet have an established route. This can be used to
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determine when/if the client needs to be sent an updated route
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when sticky sessions are used.</p>
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</dd>
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</dl>
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</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
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<div class="section">
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<h2><a name="enable" id="enable">Enabling Balancer Manager Support</a></h2>
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<p>This module <em>requires</em> the service of
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<code class="module"><a href="../mod/mod_status.html">mod_status</a></code>.
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Balancer manager enables dynamic update of balancer
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members. You can use balancer manager to change the balance
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factor or a particular member, or put it in the off line
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mode.
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</p>
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<p>Thus, in order to get the ability of load balancer management,
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<code class="module"><a href="../mod/mod_status.html">mod_status</a></code> and <code class="module"><a href="../mod/mod_proxy_balancer.html">mod_proxy_balancer</a></code>
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have to be present in the server.</p>
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<p>To enable load balancer management for browsers from the example.com
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domain add this code to your <code>httpd.conf</code>
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configuration file</p>
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<div class="example"><p><code>
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<Location /balancer-manager><br />
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SetHandler balancer-manager<br />
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<br />
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Order Deny,Allow<br />
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Deny from all<br />
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Allow from .example.com<br />
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</Location>
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</code></p></div>
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<p>You can now access load balancer manager by using a Web browser
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to access the page
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<code>http://your.server.name/balancer-manager</code></p>
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</div>
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<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
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<div class="directive-section"><h2><a name="BalancerNonce" id="BalancerNonce">BalancerNonce</a> <a name="balancernonce" id="balancernonce">Directive</a></h2>
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<table class="directive">
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<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Set the nonce used in the balancer-manager application</td></tr>
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<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>BalancerNonce Default|None|Set "value"</code></td></tr>
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<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ProxyStatus Default</code></td></tr>
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<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
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<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
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<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_proxy_balancer</td></tr>
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<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in version 2.4 and later</td></tr>
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</table>
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<p>This directive specifies the protective nonce used in the
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<code>balancer-manager</code> application page.</p>
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<p>The default is to use an automatically determined UUID-based
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nonce, to provide for further protection for the page. If set
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to <code>Set</code>, then the next argument sets the nonce to that
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value. A setting of <code>None</code> disables all nonce checking.</p>
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<div class="example"><p><code>
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BalancerNonce Set "RealGudSharedSecret"
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</code></p></div>
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<div class="note"><h3>Note</h3>
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<p>In addition to the nonce, the <code>balancer-manager</code> page
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should be protected via an ACL.</p>
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</div>
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</div>
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</div>
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<div class="bottomlang">
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<p><span>Available Languages: </span><a href="../en/mod/mod_proxy_balancer.html" title="English"> en </a> |
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<a href="../ja/mod/mod_proxy_balancer.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a></p>
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</div><div id="footer">
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<p class="apache">Copyright 2010 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>
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<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>
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