[rules-users] fireUntilHalt and timing of rule activations
Norman C
rent_my_time at yahoo.com
Wed Oct 6 02:51:21 EDT 2010
Wolfgang, so I don't improperly interpret your suggestion, it may be better if
you add your suggestion to the ticket. This is the ticket I logged:
https://jira.jboss.org/browse/JBRULES-2723
Thanks,
Norman
________________________________
From: Wolfgang Laun <wolfgang.laun at gmail.com>
To: Rules Users List <rules-users at lists.jboss.org>
Sent: Tue, October 5, 2010 11:34:53 PM
Subject: Re: [rules-users] fireUntilHalt and timing of rule activations
Norman,
if you create the Jira, please include my suggestion to make this call accept a
collection of facts without any intervening Engine activity.
Thanks
-W
2010/10/5 Norman C <rent_my_time at yahoo.com>
>
>Thanks for the suggestions. They all look like good ways to handle the
>situation I described. However, they require modifying all of the rules to
>check for the latch object and its state, which I would prefer not to do and
>doesn't seem like would be necessary.
>
>It seems to me that this is something that Drools can handle internally without
>the rules having to be written this way. Since the rules engine processes rules
>in a single thread, it's a concurrency issue. fireUntilHalt should be blocked
>when a fact is inserted/updated/retracted, until all activations as a result of
>that change in working memory are completed.
>
>
>Thoughts?
>
>Norman
>
>
>
>
>
________________________________
>From: Wolfgang Laun <wolfgang.laun at gmail.com>
>
>To: Rules Users List <rules-users at lists.jboss.org>
>Sent: Sun, October 3, 2010 10:51:08 PM
>
>Subject: Re: [rules-users] fireUntilHalt and timing of rule activations
>
>
>2010/10/4 Greg Barton <greg_barton at yahoo.com>
>
>If you don't have some way of associating the data with a particular Latch it's
>easy to get overlap when processing datasets. In general you need some way to
>group the data together. You can avoid a back reference to the Latch by having
>a Set of some sort in the Latch to which you add all data in the batch.
Which burdens all inserts and retracts to be accompanied by correpsonding
updates of the Set/Map.
If you use a Set backed by an IdentityHashMap the overhead is pretty small, and
rules look like this:
>
>
>rule "CountAs"
> dialect "java"
> salience -1
> when
> l : Latch()
> a : A( this memberOf l.dataSet )
>
> then
> retract(a);
> l.incACount();
> System.out.println("Found an A in " + l);
>end
>
>See attached project.
>
>THough I like the cleverness of using the "data in matched objects alters rule
>properties" trick, you could have just as easily had a "Latch(value == true)"
>conditional, and that would be more clear,
It was meant to emphasize the role of Latch.value as an enabler for the rule in
contrast to a regular constraint being part of the application logic. YMMV ;-)
IMO. I'm curious to see of the enabled trick would perform better, though.
>
Whichever way, there is a considerable burden associated with writing the rules
and, possibly, inserts and retracts. I wonder what the benefits of having the
session run all the time are as opposed to simply let it fire until it stops;
then do the inserts and then fireUntilHalt again? If there is, I'd opt for the
addition of an atomic insertAll(Object... objects) and then none of this
hocus-pocus would be necessary.
-W
>GreG
>
>--- On Sun, 10/3/10, Wolfgang Laun <wolfgang.laun at gmail.com> wrote:
>
>From: Wolfgang Laun <wolfgang.laun at gmail.com>
>Subject: Re: [rules-users] fireUntilHalt and timing of rule activations
>To: "Rules Users List" <rules-users at lists.jboss.org>
>Date: Sunday, October 3, 2010, 4:23 AM
>
>
>There is another way of associating a Latch object with rules, without having to
>store a reference to a Latch in objects:
>
>rule "CountAs"
>enabled ( $v )
>when
> Latch( $v : value )
> X( ... )
>
>then ... end
>
>At the beginning, insert Latch( false ), which blocks all rules with this
>construction, or modify the Latch object to false before inserting more facts.
>Then, insert the facts, and, at the end, modify Latch to true.
>
>
> Latch latch = new Latch( true );
> FactHandle fh = kSession.insert( latch );
> kSession.fireAllRules();
> latch.setValue( false );
> kSession.update( fh, latch );
>
>Of course, you can use multiple Latch objects, adding a name field with a
>specific value, so that a latch applies to a subset of rules only:
>
>
>rule "CountAs"
>
>enabled ( $v )
>
>when
>
> Latch( name == "CountAs", $v : value )
> ...
>
>But be aware that changes to Latch objects will retrigger rules that have fired
>previously; so with this approach you'll have to make sure to retract facts when
>they have been processed.
>
>
>-W
>
>
>2010/10/3 Greg Barton <greg_barton at yahoo.com>
>
>Nope, you're not missing anything. What you need is a control object of some
>sort thst's inserted after all of the "real" data is inserted. (See attached
>project for an example.) Rules will look like this, if the control object is
>called BatchLatch and data objects A:
>
>
>
>
>rule "CountAs"
>
> dialect "java"
>
> salience -1
>
> when
>
> l : Latch()
>
> a : A( latch == l )
>
> then
>
> retract(a);
>
> l.incACount();
>
> System.out.println("Found an A in " + bl);
>
>end
>
>
>
>Note that the A object being processed is tied back to the latch. This is so
>multiple latches can be processed simultaneously and their processing won't be
>intermingled. This is necessary because there's no guarantee that two Latch
>objects aren't in working memory at once. (Though you could create a rule that
>enforces this.)
>
>
>
>
>GreG
>
>
>
>--- On Sat, 10/2/10, Norman C <rent_my_time at yahoo.com> wrote:
>
>
>
>> From: Norman C <rent_my_time at yahoo.com>
>
>> Subject: [rules-users] fireUntilHalt and timing of rule activations
>
>> To: rules-users at lists.jboss.org
>
>> Date: Saturday, October 2, 2010, 10:22 AM
>
>> Hi All,
>
>>
>
>> In my app, I have a separate thread calling fireUntilHalt()
>
>> continuously. I
>
>> have quite a few rules, and I am using salience extensively
>
>> to control the order
>
>>
>
>> in which rules are executed. What I have seen (by adding
>
>> an event listener) is
>
>> that as a new fact is inserted, various rules are
>
>> activated. Often, the
>
>> fireUntilHalt will start executing fireNextItem in
>
>> DefaultAgenda before all of
>
>> the activations are complete. So if the rule with the
>
>> highest salience
>
>> value hasn't been activated at this point, then the first
>
>> rule to be fired isn't
>
>>
>
>> the correct one.
>
>>
>
>> This can be worked around by waiting for insert to return
>
>> and then calling
>
>> fireAllRules(). But it seems like the session should
>
>> block fireUntilHalt from
>
>> trying to execute activated rules until all activations are
>
>> complete. Or am I
>
>> missing something here?
>
>>
>
>> thanks,
>
>> Norman
>
>>
>
>>
>
>>
>
>>
>
>>
>
>> _______________________________________________
>
>> rules-users mailing list
>
>> rules-users at lists.jboss.org
>
>> https://lists.jboss.org/mailman/listinfo/rules-users
>
>>
>
>
>
>
>
>
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