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| <div id="preamble"><h1>Apache Module mod_proxy_balancer</h1> |
| <div class="toplang"> |
| <p><span>Available Languages: </span><a href="../en/mod/mod_proxy_balancer.html" title="English"> en </a> | |
| <a href="../ja/mod/mod_proxy_balancer.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a></p> |
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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> |
| <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>proxy_balancer_module</td></tr> |
| <tr><th><a href="module-dict.html#SourceFile">Source File:</a></th><td>mod_proxy_balancer.c</td></tr> |
| <tr><th><a href="module-dict.html#Compatibility">Compatibility:</a></th><td>Available in version 2.1 and later</td></tr></table> |
| <h3>Summary</h3> |
| |
| <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 |
| <code>HTTP</code>, <code>FTP</code> and <code>AJP13</code> protocols |
| </p> |
| |
| <p>Load balancing scheduler algorithm is provided by not this |
| module but other modules such as: |
| <code class="module"><a href="../mod/mod_lbmethod_byrequests.html">mod_lbmethod_byrequests</a></code>, |
| <code class="module"><a href="../mod/mod_lbmethod_bytraffic.html">mod_lbmethod_bytraffic</a></code> and |
| <code class="module"><a href="../mod/mod_lbmethod_bybusyness.html">mod_lbmethod_bybusyness</a></code>. |
| </p> |
| |
| <p>Thus, in order to get the ability of load balancing, |
| <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> |
| and at least one of load balancing scheduler algorithm modules have |
| to be present in the server.</p> |
| |
| <div class="warning"><h3>Warning</h3> |
| <p>Do not enable proxying until you have <a href="mod_proxy.html#access">secured your server</a>. Open proxy |
| servers are dangerous both to your network and to the Internet at |
| large.</p> |
| </div> |
| </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="#scheduler">Load balancer scheduler algorithm</a></li> |
| <li><img alt="" src="../images/down.gif" /> <a href="#example">Example of a balancer configuration</a></li> |
| <li><img alt="" src="../images/down.gif" /> <a href="#environment">Exported Environment Variables</a></li> |
| <li><img alt="" src="../images/down.gif" /> <a href="#enable">Enabling Balancer Manager Support</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> |
| </ul></div> |
| <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> |
| <div class="section"> |
| <h2><a name="scheduler" id="scheduler">Load balancer scheduler algorithm</a></h2> |
| |
| <p>At present, there are 3 load balancer scheduler algorithms available |
| for use: Request Counting, Weighted Traffic Counting and Pending Request |
| Counting. These are controlled via the <code>lbmethod</code> value of |
| the Balancer definition. See the <code class="directive"><a href="../mod/mod_proxy.html#proxypass">ProxyPass</a></code> |
| directive for more information.</p> |
| |
| </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> |
| <div class="section"> |
| <h2><a name="example" id="example">Example of a balancer configuration</a></h2> |
| |
| <p>Before we dive into the technical details, here's an example of |
| how you might use <code class="module"><a href="../mod/mod_proxy_balancer.html">mod_proxy_balancer</a></code> to provide |
| load balancing between two back-end servers: |
| </p> |
| |
| <div class="example"><p><code> |
| <Proxy balancer://mycluster><br /> |
| BalancerMember http://192.168.1.50:80<br /> |
| BalancerMember http://192.168.1.51:80<br /> |
| </Proxy><br /> |
| ProxyPass /test balancer://mycluster/ |
| </code></p></div> |
| </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> |
| <div class="section"> |
| <h2><a name="environment" id="environment">Exported Environment Variables</a></h2> |
| |
| <p>At present there are 6 environment variables exported:</p> |
| |
| <dl> |
| |
| <dt><var><a name="balancer_session_sticky" id="balancer_session_sticky">BALANCER_SESSION_STICKY</a></var></dt> |
| <dd> |
| <p>This is assigned the <var>stickysession</var> value used in the current |
| request. It is the cookie or parameter name used for sticky sessions</p> |
| </dd> |
| |
| |
| <dt><var><a name="balancer_session_route" id="balancer_session_route">BALANCER_SESSION_ROUTE</a></var></dt> |
| <dd> |
| <p>This is assigned the <var>route</var> parsed from the current |
| request.</p> |
| </dd> |
| |
| |
| <dt><var><a name="balancer_name" id="balancer_name">BALANCER_NAME</a></var></dt> |
| <dd> |
| <p>This is assigned the name of the balancer used for the current |
| request. The value is something like <code>balancer://foo</code>.</p> |
| </dd> |
| |
| |
| <dt><var><a name="balancer_worker_name" id="balancer_worker_name">BALANCER_WORKER_NAME</a></var></dt> |
| <dd> |
| <p>This is assigned the name of the worker used for the current request. |
| The value is something like <code>http://hostA:1234</code>.</p> |
| </dd> |
| |
| |
| <dt><var><a name="balancer_worker_route" id="balancer_worker_route">BALANCER_WORKER_ROUTE</a></var></dt> |
| <dd> |
| <p>This is assigned the <var>route</var> of the worker that will be |
| used for the current request.</p> |
| </dd> |
| |
| |
| <dt><var><a name="balancer_route_changed" id="balancer_route_changed">BALANCER_ROUTE_CHANGED</a></var></dt> |
| <dd> |
| <p>This is set to 1 if the session route does not match the |
| worker route (BALANCER_SESSION_ROUTE != BALANCER_WORKER_ROUTE) or the |
| session does not yet have an established route. This can be used to |
| determine when/if the client needs to be sent an updated route |
| when sticky sessions are used.</p> |
| </dd> |
| </dl> |
| |
| </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> |
| <div class="section"> |
| <h2><a name="enable" id="enable">Enabling Balancer Manager Support</a></h2> |
| |
| <p>This module <em>requires</em> the service of |
| <code class="module"><a href="../mod/mod_status.html">mod_status</a></code>. |
| Balancer manager enables dynamic update of balancer |
| members. You can use balancer manager to change the balance |
| factor or a particular member, or put it in the off line |
| mode. |
| </p> |
| |
| <p>Thus, in order to get the ability of load balancer management, |
| <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> |
| have to be present in the server.</p> |
| |
| <p>To enable load balancer management for browsers from the example.com |
| domain add this code to your <code>httpd.conf</code> |
| configuration file</p> |
| <div class="example"><p><code> |
| <Location /balancer-manager><br /> |
| SetHandler balancer-manager<br /> |
| <br /> |
| Order Deny,Allow<br /> |
| Deny from all<br /> |
| Allow from .example.com<br /> |
| </Location> |
| </code></p></div> |
| |
| <p>You can now access load balancer manager by using a Web browser |
| to access the page |
| <code>http://your.server.name/balancer-manager</code></p> |
| </div> |
| </div> |
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| <a href="../ja/mod/mod_proxy_balancer.html" hreflang="ja" rel="alternate" title="Japanese"> ja </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> |
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