diff options
Diffstat (limited to 'docs')
-rw-r--r-- | docs/manual/mod/mod_proxy_balancer.xml | 224 |
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"> </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> |