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<div id="preamble"><h1>Module Apache mod_lbmethod_byrequests</h1>
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<p><span>Langues Disponibles: </span><a href="../en/mod/mod_lbmethod_byrequests.html" hreflang="en" rel="alternate" title="English">&nbsp;en&nbsp;</a> |
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<table class="module"><tr><th><a href="module-dict.html#Description">Description:</a></th><td>Algorithme de planification avec rpartition de charge du
traitement des requtes pour le module
<code class="module"><a href="../mod/mod_proxy_balancer.html">mod_proxy_balancer</a></code></td></tr>
<tr><th><a href="module-dict.html#Status">Statut:</a></th><td>Extension</td></tr>
<tr><th><a href="module-dict.html#ModuleIdentifier">IdentificateurdeModule:</a></th><td>lbmethod_byrequests_module</td></tr>
<tr><th><a href="module-dict.html#SourceFile">FichierSource:</a></th><td>mod_lbmethod_byrequests.c</td></tr>
<tr><th><a href="module-dict.html#Compatibility">Compatibilit:</a></th><td>Dissoci de <code class="module"><a href="../mod/mod_proxy_balancer.html">mod_proxy_balancer</a></code> dans la
version 2.3</td></tr></table>
<h3>Sommaire</h3>

<p>Ce module ne fournit pas lui-mme de directive de configuration. Il
ncessite les services de <code class="module"><a href="../mod/mod_proxy_balancer.html">mod_proxy_balancer</a></code>, et
fournit la mthode de rpartition de charge <code>byrequests</code>.</p>
</div>
<div id="quickview"><a href="https://www.apache.org/foundation/contributing.html" class="badge"><img src="https://www.apache.org/images/SupportApache-small.png" alt="Support Apache!" /></a><h3>Sujets</h3>
<ul id="topics">
<li><img alt="" src="../images/down.gif" /> <a href="#requests">Algorithme d'attribution des requtes</a></li>
</ul><h3 class="directives">Directives</h3>
<p>Ce module ne fournit aucune directive.</p>
<h3>Traitement des bugs</h3><ul class="seealso"><li><a href="https://www.apache.org/dist/httpd/CHANGES_2.4">Journal des modifications de httpd</a></li><li><a href="https://bz.apache.org/bugzilla/buglist.cgi?bug_status=__open__&amp;list_id=144532&amp;product=Apache%20httpd-2&amp;query_format=specific&amp;order=changeddate%20DESC%2Cpriority%2Cbug_severity&amp;component=mod_lbmethod_byrequests">Problmes connus</a></li><li><a href="https://bz.apache.org/bugzilla/enter_bug.cgi?product=Apache%20httpd-2&amp;component=mod_lbmethod_byrequests">Signaler un bug</a></li></ul><h3>Voir aussi</h3>
<ul class="seealso">
<li><code class="module"><a href="../mod/mod_proxy.html">mod_proxy</a></code></li>
<li><code class="module"><a href="../mod/mod_proxy_balancer.html">mod_proxy_balancer</a></code></li>
<li><a href="#comments_section">Commentaires</a></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="requests" id="requests">Algorithme d'attribution des requtes</a></h2>
    
    <p>Activ via <code>lbmethod=byrequests</code>, ce planificateur 
    t conu dans le but de distribuer les requtes  tous les
    processus worker afin qu'ils traitent tous le nombre de requtes
    pour lequel ils ont t configurs. Il fonctionne de la manire
    suivante : </p>

    <p><dfn>lbfactor</dfn> correspond  la <em>quantit de travail que
    nous attendons de ce processus worker</em>, ou en d'autres termes
    son <em>quota de travail</em>. C'est une valeur normalise
    reprsentant leur part du travail  accomplir.</p>

    <p><dfn>lbstatus</dfn> reprsente <em>combien il est urgent que
    ce processus worker travaille pour remplir son quota de
    travail</em>.</p>

    <p>Le <dfn>worker</dfn> est un membre du dispositif de rpartition
    de charge, en gnral un serveur distant traitant un des protocoles
    supports.</p>

    <p>On distribue  chaque processus worker son quota de travail, puis
    on regarde celui qui a le plus besoin de travailler
    (le plus grand lbstatus). Ce processus est alors slectionn pour
    travailler, et son lbstatus diminu de l'ensemble des quotas de
    travail que nous avons distribus  tous les processus. La somme de
    tous les lbstatus n'est ainsi pas modifie, et nous pouvons
    distribuer les requtes selon nos souhaits.</p>

    <p>Si certains processus workers sont dsactivs, les autres feront
    l'objet d'une planification normale.</p>

    <div class="example"><pre><code>for each worker in workers
    worker lbstatus += worker lbfactor
    total factor    += worker lbfactor
    if worker lbstatus &gt; candidate lbstatus
        candidate = worker

candidate lbstatus -= total factor</code></pre></div>

    <p>Si un rpartiteur de charge est configur comme suit :</p>

    <table><tr><th>worker</th>
        <th class="data">a</th>
        <th class="data">b</th>
        <th class="data">c</th>
        <th class="data">d</th></tr>
<tr><th>lbfactor</th>
        <td class="data">25</td>
        <td class="data">25</td>
        <td class="data">25</td>
        <td class="data">25</td></tr>
<tr><th>lbstatus</th>
        <td class="data">0</td>
        <td class="data">0</td>
        <td class="data">0</td>
        <td class="data">0</td></tr>
</table>

    <p>Et si <var>b</var> est dsactiv, la planification suivante est
    mise en oeuvre :</p>

    <table><tr><th>worker</th>
        <th class="data">a</th>
        <th class="data">b</th>
        <th class="data">c</th>
        <th class="data">d</th></tr>
<tr><th>lbstatus</th>
        <td class="data"><em>-50</em></td>
        <td class="data">0</td>
        <td class="data">25</td>
        <td class="data">25</td></tr>
<tr><th>lbstatus</th>
        <td class="data">-25</td>
        <td class="data">0</td>
        <td class="data"><em>-25</em></td>
        <td class="data">50</td></tr>
<tr><th>lbstatus</th>
        <td class="data">0</td>
        <td class="data">0</td>
        <td class="data">0</td>
        <td class="data"><em>0</em></td></tr>
<tr><td class="data" colspan="5">(repeat)</td></tr>
</table>

    <p>C'est  dire la chronologie suivante : <var>a</var> <var>c</var>
    <var>d</var>
    <var>a</var> <var>c</var> <var>d</var> <var>a</var> <var>c</var>
    <var>d</var> ... Veuillez noter que :</p>

    <table><tr><th>worker</th>
        <th class="data">a</th>
        <th class="data">b</th>
        <th class="data">c</th>
        <th class="data">d</th></tr>
<tr><th>lbfactor</th>
        <td class="data">25</td>
        <td class="data">25</td>
        <td class="data">25</td>
        <td class="data">25</td></tr>
</table>

    <p>A le mme effet que :</p>

    <table><tr><th>worker</th>
        <th class="data">a</th>
        <th class="data">b</th>
        <th class="data">c</th>
        <th class="data">d</th></tr>
<tr><th>lbfactor</th>
        <td class="data">1</td>
        <td class="data">1</td>
        <td class="data">1</td>
        <td class="data">1</td></tr>
</table>

    <p>Ceci est d au fait que toutes les valeurs de <dfn>lbfactor</dfn>
    sont normalises et values en fonction des autres. Avec :</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">4</td>
        <td class="data">1</td></tr>
</table>

    <p>le processus <var>b</var> va, en moyenne, se voir assigner 4 fois
    plus de requtes que <var>a</var> et <var>c</var>.</p>

    <p>La configuration suivante, asymtrique, fonctionne comme on peut
    s'y attendre :</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>Aprs 10 distributions, la planification se rpte et 7
    <var>a</var> sont slectionns avec 3 <var>b</var> intercals.</p>
</div>
</div>
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