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    <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">&nbsp;</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 class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="section">
<h2><a name="traffic" id="traffic">Weighted Traffic Counting Algorithm</a></h2>
    
    <p>Enabled via <code>lbmethod=bytraffic</code>, the idea behind this
    scheduler is very similar to the Request Counting method, with
    the following changes:</p>

    <p><dfn>lbfactor</dfn> is <em>how much traffic, in bytes, we want
    this worker to handle</em>. This is also a normalized value
    representing their "share" of the amount of work to be done,
    but instead of simply counting the number of requests, we take
    into account the amount of traffic this worker has seen.</p>

    <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></tr>
<tr><th>lbfactor</th>
        <td class="data">1</td>
        <td class="data">2</td>
        <td class="data">1</td></tr>
</table>

    <p>Then we mean that we want <var>b</var> to process twice the
    amount of bytes than <var>a</var> or <var>c</var> should. It does
    not necessarily mean that <var>b</var> would handle twice as
    many requests, but it would process twice the I/O. Thus, the
    size of the request and response are applied to the weighting
    and selection algorithm.</p>

</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 foo.com
    domain add this code to your <code>httpd.conf</code>
    configuration file</p>
<div class="example"><p><code>
    &lt;Location /balancer-manager&gt;<br />
    SetHandler balancer-manager<br />
<br />
    Order Deny,Allow<br />
    Deny from all<br />
    Allow from .foo.com<br />
    &lt;/Location&gt;
</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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