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<a href="https://community.jboss.org/index.jspa" style="text-decoration: none; color: #E1E1E1">JBoss Community</a></h1>
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Using drools in a web app is my approach correct
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created by <a href="https://community.jboss.org/people/gerasalus">gerasalus</a> in <i>jBPM</i> - <a href="https://community.jboss.org/message/761632#761632">View the full discussion</a>
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<div class="jive-rendered-content"><p>Hi all,</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>some newbie questions. I'm wondering is my thinking and my architecture correct?</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>Preconditions:</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><ol><li>We have a set of rules stored in DB.Rules will be reloaded from DB only once a day</li><li>We have a set of meta-facts. Retrieval of those facts is expensive, and they only get updated once a day, after midnight - current meta-facts are immutable for a day.</li><li>We have user facts - some user specific data which we should be using together with meta-facts and producing output for specific user.</li><li>Our SLA is 150 req/s. </li></ol><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>Typical flow would be something like: we have rules together with meta facts. Along comes user with his general facts and request specific facts. For this input we run rules and produce results - calculate some data. </p><p>Basically a typical quote calculation, just we are not calculating quotes <span> :) </span></p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>Rules may change working memory  (cart explosion pattern)</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>So how would i make this work for multi user environment in a spring web apps? My ideas:</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><ol><li>Create a custom Spring scope that will cache KnowledgeBase and invalidate it once it expires (at the beginning of new day)</li><li>Cache meta-facts (they are expensive to retrieve) for given time</li><li>For each user request (user comes in with its own facts) - create a new StatefulKnowledgeSession from existing KnowledgeBase byt inserting meta-facts and user specific facts and execute fireAllRules</li><li>Retrieve the result and dispose the StatefulKnowledgeSession()</li></ol><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>As i unserstand, if my rules are modifying working memory, i cannot reuse StatefulKnowledgeSession for different users (as they bring their own facts).  Is there a better approach ? By reading forums and mailing lists i have mixed data about StatefulKnowledgeSession creation. There are threads that state cpu spikes while creating sessions.</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>Maybe i should be considering pool of StatefulKnowledgeSession and inserting/retracing user facts while keeping meta-facts?</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>Thanks!</p></div>
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