Commit a75cc194 authored by Mladen Turk's avatar Mladen Turk
Browse files

Add desription for schedlurer algo and 

balancer manager

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@106707 13f79535-47bb-0310-9956-ffa450edef68
parent 1ee2674c

docs/manual/mod/mod_proxy_balancer.html.en

+192 −1
Original line number Diff line number Diff line
@@ -49,11 +49,202 @@ load balancing </td></tr> 
<div id="quickview"><h3 class="directives">Directives</h3>

<p>This module provides no

            directives.</p>

<h3>See also</h3>

<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="#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>The idea behind this scheduler is the following:</p>

    <p><strong>lbfactor</strong> is <em>how much we expect this worker

    to work</em>, or <em>the workers's work quota</em>.</p>

    <p><strong>lbstatus</strong> is <em>how urgent this worker has to work

    to fulfill its quota of work</em>.</p>

    <p>The <strong>worker</strong> 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.(*)</p>

    <p>If some workers are disabled, the others will

    still be scheduled correctly.</p>

    <p>If a balancer is configured as follows:</p>

    

        

<code>

  <table>

    <tr>

        <td width="80">worker</td>

        <td width="30" style="text-align: right;">a</td>

        <td width="30" style="text-align: right;">b</td>

        <td width="30" style="text-align: right;">c</td>

        <td width="30" style="text-align: right;">d</td>

    </tr>

    <tr>

        <td>lbfactor</td>

        <td style="text-align: right;">25</td>

        <td style="text-align: right;">25</td>

        <td style="text-align: right;">25</td>

        <td style="text-align: right;">25</td>

    </tr>

    <tr>

        <td>lbstatus</td>

        <td style="text-align: right;">0</td>

        <td style="text-align: right;">0</td>

        <td style="text-align: right;">0</td>

        <td style="text-align: right;">0</td>

    </tr>



  </table>

</code>    

    <p>And b gets disabled, the following schedule is produced:</p>

<code>

  <table>

    <tr>

        <td width="80">lbstatus</td>

        <td width="30" style="text-align: right;">-50</td>

        <td width="30" style="text-align: right;">0</td>

        <td width="30" style="text-align: right;">25</td>

        <td width="30" style="text-align: right;">25</td>

    </tr>

    <tr>

        <td>lbstatus</td>

        <td style="text-align: right;">-25</td>

        <td style="text-align: right;">0</td>

        <td style="text-align: right;">-25</td>

        <td style="text-align: right;">50</td>

    </tr>

    <tr>

        <td>lbstatus</td>

        <td style="text-align: right;">0</td>

        <td style="text-align: right;">0</td>

        <td style="text-align: right;">0</td>

        <td style="text-align: right;">0</td>

    </tr>

    <tr>

        <td colspan="5">(repeat)</td>

    </tr>

  </table>

</code>

    <p>That is it schedules: a c d a c d a c d ...</p>

    <p>The following asymmetric configuration works as one would expect:</p>

<code>

  <table>

    <tr>

        <td width="80">worker</td>

        <td width="30" style="text-align: right;">a</td>

        <td width="30" style="text-align: right;">b</td>

    </tr>

    <tr>

        <td>lbfactor</td>

        <td style="text-align: right;">70</td>

        <td style="text-align: right;">30</td>

    </tr>

    <tr>

        <td colspan="3">&nbsp;</td>

    </tr>

    <tr>

        <td>lbstatus</td>

        <td style="text-align: right;">-30</td>

        <td style="text-align: right;">30</td>

    </tr>

    <tr>

        <td>lbstatus</td>

        <td style="text-align: right;">40</td>

        <td style="text-align: right;">-40</td>

    </tr>

    <tr>

        <td>lbstatus</td>

        <td style="text-align: right;">10</td>

        <td style="text-align: right;">-10</td>

    </tr>

    <tr>

        <td>lbstatus</td>

        <td style="text-align: right;">-20</td>

        <td style="text-align: right;">20</td>

    </tr>

    <tr>

        <td>lbstatus</td>

        <td style="text-align: right;">-50</td>

        <td style="text-align: right;">50</td>

    </tr>

    <tr>

        <td>lbstatus</td>

        <td style="text-align: right;">20</td>

        <td style="text-align: right;">-20</td>

    </tr>

    <tr>

        <td>lbstatus</td>

        <td style="text-align: right;">-10</td>

        <td style="text-align: right;">10</td>

    </tr>

    <tr>

        <td>lbstatus</td>

        <td style="text-align: right;">-40</td>

        <td style="text-align: right;">40</td>

    </tr>

    <tr>

        <td>lbstatus</td>

        <td style="text-align: right;">30</td>

        <td style="text-align: right;">-30</td>

    </tr>

    <tr>

        <td>lbstatus</td>

        <td style="text-align: right;">0</td>

        <td style="text-align: right;">0</td>

    </tr>

    <tr>

        <td colspan="3">(repeat)</td>

    </tr>

  </table>

</code>



    <p>That is after 10 schedules, the schedule repeats and 7 a are selected

    with 3 b 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="enable" id="enable">Enabling Balancer Manager Support</a></h2>

    

    <p>Balancer manager enables dynamic update of balancer

    members. You can use balancer manager to change the balace

    factor or a particular member, or put it in the off line

    mode.</p>

    <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 balace

    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>

<div class="bottomlang">

<p><span>Available Languages: </span><a href="../en/mod/mod_proxy_balancer.html" title="English">&nbsp;en&nbsp;</a> |

docs/manual/mod/mod_proxy_balancer.xml

+187 −0
Original line number Diff line number Diff line
@@ -48,4 +48,191 @@ load balancing </description> 
</summary>

<seealso><module>mod_proxy</module></seealso>



<section id="scheduler">

    <title>Load balancer scheduler algorithm</title>

    <p>The idea behind this scheduler is the following:</p>

    <p><strong>lbfactor</strong> is <em>how much we expect this worker

    to work</em>, or <em>the workers's work quota</em>.</p>

    <p><strong>lbstatus</strong> is <em>how urgent this worker has to work

    to fulfill its quota of work</em>.</p>

    <p>The <strong>worker</strong> 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.(*)</p>

    <p>If some workers are disabled, the others will

    still be scheduled correctly.</p>

    <p>If a balancer is configured as follows:</p>

    

    <!-- Very ugly, but i can not make the table right aligned -->    

<code>

  <table>

    <tr>

        <td width="80">worker</td>

        <td width="30" style="text-align: right;">a</td>

        <td width="30" style="text-align: right;">b</td>

        <td width="30" style="text-align: right;">c</td>

        <td width="30" style="text-align: right;">d</td>

    </tr>

    <tr>

        <td>lbfactor</td>

        <td style="text-align: right;">25</td>

        <td style="text-align: right;">25</td>

        <td style="text-align: right;">25</td>

        <td style="text-align: right;">25</td>

    </tr>

    <tr>

        <td>lbstatus</td>

        <td style="text-align: right;">0</td>

        <td style="text-align: right;">0</td>

        <td style="text-align: right;">0</td>

        <td style="text-align: right;">0</td>

    </tr>



  </table>

</code>    

    <p>And b gets disabled, the following schedule is produced:</p>

<code>

  <table>

    <tr>

        <td width="80">lbstatus</td>

        <td width="30" style="text-align: right;">-50</td>

        <td width="30" style="text-align: right;">0</td>

        <td width="30" style="text-align: right;">25</td>

        <td width="30" style="text-align: right;">25</td>

    </tr>

    <tr>

        <td>lbstatus</td>

        <td style="text-align: right;">-25</td>

        <td style="text-align: right;">0</td>

        <td style="text-align: right;">-25</td>

        <td style="text-align: right;">50</td>

    </tr>

    <tr>

        <td>lbstatus</td>

        <td style="text-align: right;">0</td>

        <td style="text-align: right;">0</td>

        <td style="text-align: right;">0</td>

        <td style="text-align: right;">0</td>

    </tr>

    <tr>

        <td colspan="5">(repeat)</td>

    </tr>

  </table>

</code>

    <p>That is it schedules: a c d a c d a c d ...</p>

    <p>The following asymmetric configuration works as one would expect:</p>

<code>

  <table>

    <tr>

        <td width="80">worker</td>

        <td width="30" style="text-align: right;">a</td>

        <td width="30" style="text-align: right;">b</td>

    </tr>

    <tr>

        <td>lbfactor</td>

        <td style="text-align: right;">70</td>

        <td style="text-align: right;">30</td>

    </tr>

    <tr>

        <td colspan="3">&nbsp;</td>

    </tr>

    <tr>

        <td>lbstatus</td>

        <td style="text-align: right;">-30</td>

        <td style="text-align: right;">30</td>

    </tr>

    <tr>

        <td>lbstatus</td>

        <td style="text-align: right;">40</td>

        <td style="text-align: right;">-40</td>

    </tr>

    <tr>

        <td>lbstatus</td>

        <td style="text-align: right;">10</td>

        <td style="text-align: right;">-10</td>

    </tr>

    <tr>

        <td>lbstatus</td>

        <td style="text-align: right;">-20</td>

        <td style="text-align: right;">20</td>

    </tr>

    <tr>

        <td>lbstatus</td>

        <td style="text-align: right;">-50</td>

        <td style="text-align: right;">50</td>

    </tr>

    <tr>

        <td>lbstatus</td>

        <td style="text-align: right;">20</td>

        <td style="text-align: right;">-20</td>

    </tr>

    <tr>

        <td>lbstatus</td>

        <td style="text-align: right;">-10</td>

        <td style="text-align: right;">10</td>

    </tr>

    <tr>

        <td>lbstatus</td>

        <td style="text-align: right;">-40</td>

        <td style="text-align: right;">40</td>

    </tr>

    <tr>

        <td>lbstatus</td>

        <td style="text-align: right;">30</td>

        <td style="text-align: right;">-30</td>

    </tr>

    <tr>

        <td>lbstatus</td>

        <td style="text-align: right;">0</td>

        <td style="text-align: right;">0</td>

    </tr>

    <tr>

        <td colspan="3">(repeat)</td>

    </tr>

  </table>

</code>



    <p>That is after 10 schedules, the schedule repeats and 7 a are selected

    with 3 b interspersed.</p>

</section>



<section id="enable">

    <title>Enabling Balancer Manager Support</title>

    <p>Balancer manager enables dynamic update of balancer

    members. You can use balancer manager to change the balace

    factor or a particular member, or put it in the off line

    mode.</p>

    <p>This module <em>requires</em> the service of 

    <module>mod_status</module>.

    Balancer manager enables dynamic update of balancer

    members. You can use balancer manager to change the balace

    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,

    <module>mod_status</module> and <module>mod_proxy_balancer</module>

    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>

<example>

    &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;

</example>



    <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>

</section>



</modulesynopsis>