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-rw-r--r--docs/manual/mod/mod_proxy_balancer.xml224
1 files changed, 94 insertions, 130 deletions
diff --git a/docs/manual/mod/mod_proxy_balancer.xml b/docs/manual/mod/mod_proxy_balancer.xml
index c759ed0076..403c36c13c 100644
--- a/docs/manual/mod/mod_proxy_balancer.xml
+++ b/docs/manual/mod/mod_proxy_balancer.xml
@@ -51,149 +51,113 @@ load balancing </description>
<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
+
+ <p><dfn>lbfactor</dfn> 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
+
+ <p><dfn>lbstatus</dfn> 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>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.(*)</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>
+ <table style="data">
+ <tr><th>worker</th>
+ <th>a</th>
+ <th>b</th>
+ <th>c</th>
+ <th>d</th></tr>
+ <tr><th>lbfactor</th>
+ <td>25</td>
+ <td>25</td>
+ <td>25</td>
+ <td>25</td></tr>
+ <tr><th>lbstatus</th>
+ <td>0</td>
+ <td>0</td>
+ <td>0</td>
+ <td>0</td></tr>
+ </table>
+
+ <p>And <var>b</var> gets disabled, the following schedule is produced:</p>
+
+ <table style="data">
+ <tr><th>worker</th>
+ <th>a</th>
+ <th>b</th>
+ <th>c</th>
+ <th>d</th></tr>
+ <tr><th>lbstatus</th>
+ <td>-50</td>
+ <td>0</td>
+ <td>25</td>
+ <td>25</td></tr>
+ <tr><th>lbstatus</th>
+ <td>-25</td>
+ <td>0</td>
+ <td>-25</td>
+ <td>50</td></tr>
+ <tr><th>lbstatus</th>
+ <td>0</td>
+ <td>0</td>
+ <td>0</td>
+ <td>0</td></tr>
+ <tr><td colspan="5">(repeat)</td></tr>
+ </table>
+
<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>
+
+ <table style="data">
+ <tr><th>worker</th>
+ <th>a</th>
+ <th>b</th></tr>
+ <tr><th>lbfactor</th>
+ <td>70</td>
+ <td>30</td></tr>
+ <tr><th>lbstatus</th>
+ <td>-30</td>
+ <td>30</td></tr>
+ <tr><th>lbstatus</th>
+ <td>40</td>
+ <td>-40</td></tr>
+ <tr><th>lbstatus</th>
+ <td>10</td>
+ <td>-10</td></tr>
+ <tr><th>lbstatus</th>
+ <td>-20</td>
+ <td>20</td></tr>
+ <tr><th>lbstatus</th>
+ <td>-50</td>
+ <td>50</td></tr>
+ <tr><th>lbstatus</th>
+ <td>20</td>
+ <td>-20</td></tr>
+ <tr><th>lbstatus</th>
+ <td>-10</td>
+ <td>10</td></tr>
+ <tr><th>lbstatus</th>
+ <td>-40</td>
+ <td>40</td></tr>
+ <tr><th>lbstatus</th>
+ <td>30</td>
+ <td>-30</td></tr>
+ <tr><th>lbstatus</th>
+ <td>0</td>
+ <td>0</td></tr>
+ <tr><td colspan="3">(repeat)</td></tr>
+ </table>
<p>That is after 10 schedules, the schedule repeats and 7 a are selected
with 3 b interspersed.</p>