[rules-users] Drools 5 PseudoClock with StatelessKnowledgeSession

[Edson Tirelli]

   I think there might be a conceptual problem here. Stateless sessions are
supposed to take a snapshot of facts (and/or events) and run all rules for
them and dispose the session. Since it is a snapshot, there is no concept of
time flow during the execution and so it can only run in the equivalent of
CLOUD mode for stateful sessions. That is why no session clock is provided
for stateless sessions.

   In order to use the SessionClock, one needs to use a stateful session
configured in STREAM mode.

   I believe we can add features in the future like the ability to run a
session with a given reference time, even if it does not involve time flow,
but that is not there. Also, since date-effective and date-expiration are
really old features, from the drools 2-3 versions, and they have quite a
number of limitations, you are probably better using "enabled" expressions
than using those attributes.

   Edson


2011/9/29 Mark Proctor <mproctor at codehaus.org>

>  Look at the interval timer test here from line 254 onwards, and the
> subsequent cron tests:
>
> https://github.com/droolsjbpm/drools/blob/master/drools-compiler/src/test/java/org/drools/integrationtests/TimerAndCalendarTest.java#L254
>
>
>
> On 13/10/2009 00:32, Ben Scott wrote:
>
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> I'm wanting to use the date-effective and date-expiry rule metadata to add
> date specific rule variants within my app. To test these I was planning on
> using the pseudo clock and setting the expected date prior to executing the
> rules within a StatelessKnowledgeSession. I can set the clock easily enough,
> but can't understand why the getSessionClock() method is missing? It's on
> the StatefulKnowledgeSession, but not on the Stateless.
> I'm initialising the session like this:
> SessionConfiguration sessionConfiguration = new SessionConfiguration();
> sessionConfiguration.setClockType( ClockType.PSEUDO_CLOCK );
> StatelessKnowledgeSession session =
> _testKnowledgeBase.newStatelessKnowledgeSession(sessionConfiguration);
> The only thing I could think of to set the pseudo clock was to write a
> command something like:
> private static class SetPseudoClockCommand implements
> org.drools.process.command.Command<Boolean> {
> public Boolean execute(ReteooWorkingMemory session) {
> // Set the clock to the current date
> pseudoSessionClock.advanceTime(new DateTime().getMillis(),
> TimeUnit.MILLISECONDS);
> // Add a couple of days
> pseudoSessionClock.advanceTime(2, TimeUnit.DAYS);
> return true;
> }
> }
> But this doesn't appear to take any effect whilst rules are running.
> Is there another way to get programmatic access to the session clock, or
> some better way of changing the underlying date prior to rule execution?
> Ben.
>
>
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-- 
  Edson Tirelli
  JBoss Drools Core Development
  JBoss by Red Hat @ www.jboss.com
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