February 2010 - rules-users - Jboss List Archives

Is Drools the right choice for my use case?

by Tong Wang

I'll use a university's library system to explain my use case. Students register in the library system and provide their profile: gender, age, department, previously completed courses, currectly registered courses, books already borrowed, etc. Each book in the library system will define some borrowing rules based on students' profile, for example, a textbook for the computer algorithm can only be borrowed by students currently registered with that class; another textbook may only be borrowed by students in the math department; there could also be rules such that students can only borrow 2 computer networking book at most. As a result of the borrowing rules, when a student searches/browses in the library system, he will only see the books that can be borrowed by him. So, the requirement really comes down to the line of efficiently generating the list of books that a student is eligible to borrow. Here is how I vision the design using Drools - each book will have a rule with a few field constraints on the student profile as LHS, the RHS of the book rule simply adds the book id to a global result list, then all the book rules are loaded into a RuleBase. When a student searches/browsers the library system, a stateless session is created from the RuleBase and the student's profile is asserted as the fact, then every book that the student can borrow will fire its book rule and you get the complete list of books that the students can borrow in the global result list. A few assumptions: the library will handle millions of books; I don't expect the book rule be too complicated, 3 simple field constraints for each rule on average at the most; the number of students that the system needs to handle is in the range of 100K, so the load is fairly heavy. My questions are: how much memory will Drools take if loaded with a million book rules? How fast will it be for all those million rules to fire? If Drools is the right fit, I'd like to hear some best practices in designing such a system from you experienced users. Thanks.

16 years, 4 months

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Triggers on Start node

by paulB

I have created a start node in my RuleFlow as follows: <start id="1" name="Start" x="171" y="16" width="80" height="40"> <triggers> <trigger type="event"> <eventFilters> <eventFilter type="eventType" eventType="SurveyCompleted" /> </eventFilters> </trigger> </triggers> </start> I'm additionally using the following code snippet in RHS of a rule: drools.getKnowledgeRuntime().signalEvent( type, eventData ); Works great, but I am unsure how to get eventData and assign it to a variable in the started process. I see there is an element under <trigger>: <mapping type="in" from="something" to="SomeVar" /> However, I am unsure if this is the element to use. If so, what would be the appropriate value in the "from" attribute? Thanks! -- View this message in context: http://n3.nabble.com/Triggers-on-Start-node-tp209420p209420.html Sent from the Drools - User mailing list archive at Nabble.com.

16 years, 4 months

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Rules writing best practice?

by Brice Figureau

Hi, Is there a rules writing best practice document somewhere? I'm asking the question because as a newbie rule writer (which doesn't know anything about the underlying drools matching algorithm), I'm wondering if my rules will behave gracefully. For instance, I (ab)use a lot the from/accumulate to bring in the knowledge some external facts coming from some DAO. All my rules use one time or more the same "from dao.getInformationFromDatabase( <inserted fact> )" structure and I'm not sure the algorithm is smart enough to cache this information which is constant for a given inserted fact. Should I instead insert all this information as facts prior to the rules firing? -- Brice Figureau My Blog: http://www.masterzen.fr/

16 years, 4 months

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"not contains" on Java5 enumeration

by Ray Ploski

I'm not certain, but it looks like the Operator "not contains"[1] works fine with strings but not Enumerations. Would someone please confirm or correct the rule syntax? Thank you. Given: rule "Absence_Accumulation_Rule" when $slice : TimeSlice( classifiers contains(TimeSliceClassifiers.ABSENCE), classifiers contains(TimeSliceClassifiers.OT), classifiers not contains (TimeSliceClassifiers.COUNT_TO_FLSA), then System.out.println("Absence: Count to overtime but not FLSA"); end public enum TimeSliceClassifiers { INSIDE_SCHEDULE, OUTSIDE_SCHEDULE, WORKED, ABSENCE, APPROVED, OVERTIME_REQUEST, CASH,INVOLUNTARY, COUNT_TO_OT, COUNT_TO_FLSA, OT, STRAIGHT, PREMIUM, EC0100, EC1400, EC1405 } public class TimeSlice { private Date start; private Date end; private int elapsed; private Set<TimeSliceClassifiers> classifiers; private boolean sliceCreatedByRules = false; } Provides the following error: [ERR 103] Line 110:21 rule 'in_key' failed predicate: {(validateIdentifierKey(DroolsSoftKeywords.IN))}? in rule "Absence_Accumulation_Rule" in pattern TimeSlice

16 years, 4 months

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StatefulKnowledgeSession synchronization problem

by heldeen

Hello, Using Drools 5.1.0.M1. I am running into a blocking problem when I concurrently try to update a fact in my knowledge session, which is fireUntilHalt() in its own thread, from another thread, an updator thread. I know that only these 2 threads are ever accessing each knowledge session. Has anyone else run into this problem? I am including the relavant details and can provide a working example if need be. The block happens randomly anywhere from 20 - 1000's of sessions. I consistantly get this stack trace from the blocked thread: org.drools.common.AbstractWorkingMemory.executeQueuedActions(AbstractWorkingMemory.java:1540) org.drools.common.AbstractWorkingMemory.update(AbstractWorkingMemory.java:1529) org.drools.common.AbstractWorkingMemory.update(AbstractWorkingMemory.java:1403) org.drools.impl.StatefulKnowledgeSessionImpl.update(StatefulKnowledgeSessionImpl.java:248) ... I have a simple drools knowledge base that is a basic rule flow [Start -> Rule Flow Group -> Event Wait -> Rule Flow Group -> End] I build a knowledge base like this: KnowledgeBaseConfiguration knowledgeBaseConfiguration = KnowledgeBaseFactory.newKnowledgeBaseConfiguration(); knowledgeBaseConfiguration.setOption(AssertBehaviorOption.EQUALITY); knowledgeBaseConfiguration.setOption(MBeansOption.ENABLED); KnowledgeBase knowledgeBase = KnowledgeBaseFactory.newKnowledgeBase(knowledgeBaseConfiguration); KnowledgeBuilder kbuilder = KnowledgeBuilderFactory.newKnowledgeBuilder(); kbuilder.add(ResourceFactory.newClassPathResource(CHANGE_SET_XML, getClass()), ResourceType.CHANGE_SET); if (kbuilder.hasErrors()) { throw new IllegalArgumentException("Unable to build knowledge"); } knowledgeBase.addKnowledgePackages(kbuilder.getKnowledgePackages()); My basic test fact is: public class Fact() { String name; boolean isReady; //getters and setters } I have a fixed thread pool (Sun's ExecutorService.newFixedThreadPool() with 20 threads). Each session is submitted from a for loop of 0 to 100000 where it generates a simple fact with Fact.name = "fact"+i and Fact.isReady = false, then puts it in an array like so: final Object[] facts... fixedPoolExecutor.submit(new Runnable() { @Override public void run() { StatefulKnowledgeSession knowledgeSession = null; try { knowledgeSession = knowledgeBase.newStatefulKnowledgeSession(); //put it in a ConcurrentHashMap keyed by session id. ... for (Object fact : facts) { knowledgeSession.insert(fact); } //add session completion halt event - omiting other unused methods knowledgeSession.addEventListener(new ProcessEventListener() { @Override public void afterProcessCompleted(ProcessCompletedEvent event) { knowledgeSession.halt(); } }); knowledgeSession.startProcess(PROCESS_ID); knowledgeSession.fireUntilHalt(); } finally { if (knowledgeSession != null) { knowledgeSession.dispose(); } } }); I have a single thread executor (Sun's ExecutorService.newSingleThreadExecutor()) that is used to update these sessions (basically set the Fact.isReady from false to true for the EventWait in my rule flow): final int sessionId... final Object[] facts... singleThreadExecutor.submit(new Runnable() { @Override public void run() { StatefulKnowledgeSession knowledgeSession = null; try { knowledgeSession = ... from ConcurrentHashMap based on sessionId FactHandle factHandle = knowledgeSession.getFactHandle(fact); if (null != factHandle) { knowledgeSession.update(factHandle, fact);//This is where it blocks and never returns } else { knowledgeSession.insert(fact); } }); -Heath -- View this message in context: http://n3.nabble.com/StatefulKnowledgeSession-synchronization-problem-tp1... Sent from the Drools - User mailing list archive at Nabble.com.

16 years, 4 months

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Re: [rules-users] rules-users Digest, Vol 39, Issue 30

by Régis Ramillien

Hello, It works well for me without doing anything special. Perhaps the problem comes from your rules? Have you assigned variables to your facts ? Can you paste a example of a rule ? 2010/2/11 <rules-users-request(a)lists.jboss.org> > Send rules-users mailing list submissions to > rules-users(a)lists.jboss.org > > To subscribe or unsubscribe via the World Wide Web, visit > https://lists.jboss.org/mailman/listinfo/rules-users > or, via email, send a message with subject or body 'help' to > rules-users-request(a)lists.jboss.org > > You can reach the person managing the list at > rules-users-owner(a)lists.jboss.org > > When replying, please edit your Subject line so it is more specific > than "Re: Contents of rules-users digest..." > > > Today's Topics: > > 1. drools execution server (Kessler Bortoluzzi, Mariana) > > > ---------------------------------------------------------------------- > > Message: 1 > Date: Thu, 11 Feb 2010 10:01:07 +0100 > From: "Kessler Bortoluzzi, Mariana" <MKB(a)compugroup.com> > Subject: [rules-users] drools execution server > To: <rules-users(a)lists.jboss.org> > Message-ID: > <7E4DCDD4DFDF9545B2676F6CDD8EC39C04B9470C(a)smxko5.koblenz.cg.local> > Content-Type: text/plain; charset="us-ascii" > > Hello everyone, > > > > I am trying to use the drools execution server, and was able to post XML > requests to it and get an XML answer, but I could not change the > inOutFacts using my rules. > > Except for the "Execution Server is running" page, I didn't find any > documentation about it. > > Is there any other documentation available? > > > > Mariana > > > > -------------- next part -------------- > An HTML attachment was scrubbed... > URL: > http://lists.jboss.org/pipermail/rules-users/attachments/20100211/d7b8800... > > ------------------------------ > > _______________________________________________ > rules-users mailing list > rules-users(a)lists.jboss.org > https://lists.jboss.org/mailman/listinfo/rules-users > > > End of rules-users Digest, Vol 39, Issue 30 > ******************************************* >

16 years, 4 months

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CEP Rule question

by Glenn Macgregor

Hi All, Thanks for all the help so far I could not have gotten this far this fast without it. I have a couple questions regarding windows, accumulate and CEP. * Is this a valid rule: $param : Parameter(name == "testParam") $uEvent : ParameterUpdateEvent(name == $param.name, $value : value) over window:length(5) from entry-point "EPOne" The above rule compiles and runs but the issue is I see: OBJECT RETRACTED value:ie.pk.SystemsManagement.Alerting.ParameterUpdateEvent@19ea173 factId: 6 After inserting each event, I would think the length window would fill up before any are retracted. * Is there anyway to tell if a window is full, I don't want to hit the consequence if the window is not yet full. * Is there a way to name windows, my use case is as follows: o Drools application is reading updates from an ActiveMQ bus and turning them into ParamUpdateEvents and inserting each event into EPOne o Each of these parameter updates contains one param value, so I could get an update for param1 then an update for param2... o Is it possible to have one rule which would sum the last 5 values of param1 and sum the last 5 values of param2. I can only get it to sum the last 5 updates without regard for wich param it is I hope this somewhat clear. Thanks for you help. Glenn

16 years, 4 months

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Category Rules - Guvnor

by Amit Kumar

Hi Folks, I am looking at the category rules and have a scenario to use it. Goes like this Person Name String City String income int I want to categorize the rules in states -US -- NewYork -- Seatle -- SanFrancisco I have created 3 rules rule "people living in NY" when Person(city="NewYork" then end rule "people living in Seatle" when Person(city="Seatle" then end rule "people living in SFO" when Person(city="SanFrancisco" then end I associated the above rules with appropriate categories Then I create tax rules rule "ny tax" -- category "NewYork" when Person() then Log .. Tax = 10% end rule "WA tax" -- category "Seatle" when Person() then Log .. Tax = 20% end rule "ny tax" -- category "NewYork" when Person() then Log .. Tax = 10% end When I create a object in test scenario of person type .. then all the rules get executed.. The category rule is not having any effect Is there any documentation on how this works?? Thanks Amit

16 years, 5 months

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drools execution server

by Kessler Bortoluzzi, Mariana

Hello everyone, I am trying to use the drools execution server, and was able to post XML requests to it and get an XML answer, but I could not change the inOutFacts using my rules. Except for the "Execution Server is running" page, I didn't find any documentation about it. Is there any other documentation available? Mariana

16 years, 5 months

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Re: [rules-users] CEP Error

by Glenn Macgregor

Hi Nicolas, Thanks for the response. The strange thing is I do not get this error when I run inside the debugger with the same facts. This made me believe it is a timing issue. I am using the latest stable drools - 5.0.1 Thanks Glenn ________________________________ From: rules-users-bounces(a)lists.jboss.org To: Rules Users List Sent: Wed Feb 10 18:18:57 2010 Subject: Re: [rules-users] CEP Error Hi, It says that the $param is null so $param.name<http://param.name>() cannot be called regards Nicolas 2010/2/10 Glenn Macgregor <gmacgregor(a)pocketkings.ie<mailto:gmacgregor@pocketkings.ie>> Hi All, I have a simple CEP test case which I am working through. I am currently getting a NullPointerException in the Consequence and have no idea why. Rule: rule "Param Update Event Rule" when $pue : ParameterUpdateEvent(name == "testParam2", $param : param) from entry-point "ParamUpdateStream" then #System.out.println("Param '" + $pue.getName() + "' has been updated to " + $pue.getValue()); System.out.println("HERE!!! " + $param + " " + $param.name<http://param.name>()); End Exception & Debug: OBJECT ASSERTED value:ie.PocketKings.SystemsManagement.Alerting.ParameterUpdateEvent@1265109 factId: 2 OBJECT RETRACTED value:ie.PocketKings.SystemsManagement.Alerting.ParameterUpdateEvent@1265109 factId: 2 OBJECT ASSERTED value:ie.PocketKings.SystemsManagement.Alerting.ParameterUpdateEvent@5e8d7d factId: 3 OBJECT RETRACTED value:ie.PocketKings.SystemsManagement.Alerting.ParameterUpdateEvent@5e8d7d factId: 3 ACTIVATION CREATED rule:Param Update Event Rule activationId:Param Update Event Rule [4, 0] declarations: $pue=ie.PocketKings.SystemsManagement.Alerting.ParameterUpdateEvent@19b4748(4); $param=ie.PocketKings.SystemsManagement.Alerting.Parameter@2431b9(4) Exception in thread "Thread-3" BEFORE ACTIVATION FIRED rule:Param Update Event Rule activationId:Param Update Event Rule [4, 0] declarations: $pue=ie.PocketKings.SystemsManagement.Alerting.ParameterUpdateEvent@19b4748(4); $param=ie.PocketKings.SystemsManagement.Alerting.Parameter@2431b9(4) OBJECT RETRACTED value:ie.PocketKings.SystemsManagement.Alerting.ParameterUpdateEvent@19b4748 factId: 4 OBJECT ASSERTED value:ie.PocketKings.SystemsManagement.Alerting.ParameterUpdateEvent@19b4748 factId: -1 org.drools.runtime.rule.ConsequenceException: java.lang.NullPointerException at org.drools.runtime.rule.impl.DefaultConsequenceExceptionHandler.handleException(DefaultConsequenceExceptionHandler.java:23) at org.drools.common.DefaultAgenda.fireActivation(DefaultAgenda.java:943) at org.drools.common.DefaultAgenda.fireNextItem(DefaultAgenda.java:885) at org.drools.common.DefaultAgenda.fireUntilHalt(DefaultAgenda.java:1065) at org.drools.common.AbstractWorkingMemory.fireUntilHalt(AbstractWorkingMemory.java:701) at org.drools.common.AbstractWorkingMemory.fireUntilHalt(AbstractWorkingMemory.java:678) at org.drools.impl.StatefulKnowledgeSessionImpl.fireUntilHalt(StatefulKnowledgeSessionImpl.java:195) at ie.PocketKings.SystemsManagement.Alerting.SessionRunner.run(SessionRunner.java:13) at java.lang.Thread.run(Unknown Source) Caused by: java.lang.NullPointerException at org.drools.base.ie.PocketKings.SystemsManagement.Alerting.ParameterUpdateEvent6011238$getParam.getValue(Unknown Source) at org.drools.base.ClassFieldReader.getValue(ClassFieldReader.java:91) at org.drools.rule.Declaration.getValue(Declaration.java:244) at ie.PocketKings.SystemsManagement.Alerting.Rule_Param_Update_Event_Rule_0ConsequenceInvoker.evaluate(Rule_Param_Update_Event_Rule_0ConsequenceInvoker.java:16) at org.drools.common.DefaultAgenda.fireActivation(DefaultAgenda.java:934) ... 7 more OBJECT ASSERTED value:ie.PocketKings.SystemsManagement.Alerting.ParameterUpdateEvent@19fdbcb factId: 5 Could it be that my Event object is getting destroyed before the consequence is run, is that what “OBJECT RETRACKED” means in this case? Thanks Glenn _______________________________________________ rules-users mailing list rules-users(a)lists.jboss.org<mailto:rules-users@lists.jboss.org> https://lists.jboss.org/mailman/listinfo/rules-users

16 years, 5 months

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rules-users February 2010