Drools: Having trouble with drools event processing - drools

Question

I am quite new to drools.
I am working on an application where my drools engine will get a series of event every second. I need to see if all the events in last 10 seconds has attribute value below 10, if the condition is true, I have to do some processing. Here is the example code which I tried, Please help me understand and resolve the issue.
My Rule file.....
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Date;
declare Employee
#role (event)
#expires(10s)
end
// Using timer to ensure rule processing starts only after 10 secs,
//else processing starts as soon as first event comes in
rule "Test Timer"
no-loop true
10timer(int: 5s)
when
$E : Employee()
$total : Number( doubleValue < 1 )
from accumulate( Employee( Age > 10 ), count() )
then
System.out.println( $E.getName() + " is crossing the threshold of 20");
retract($E);
end
And Main class
// import classes removed from here...
public class MainClass {
/**
* #param args
*/
public static void main(String[] args){
//Create KnowledgeBase...
KnowledgeBase knowledgeBase = createKnowledgeBase();
//Create a stateful session
StatefulKnowledgeSession session = knowledgeBase.newStatefulKnowledgeSession();
// KnowledgeRuntimeLogger logger = KnowledgeRuntimeLoggerFactory.newConsoleLogger(session);
try {
// Using random generator to simulate the data.
int randomInt=0;
Random randomGenerator = new Random();
DateFormat dateFormat = new SimpleDateFormat("yyyy/MM/dd HH:mm:ss");
Date date = null;
while (true) {
Thread.sleep(1000);
date = new Date();
randomInt = randomGenerator.nextInt(12);
//Create Facts and insert them
Employee emp = new Employee();
emp.setName("Anurag" + randomInt);
emp.setAge(randomInt);
//LOAD THE FACT AND FIREEEEEEEEEEEEEEEEEEE............
System.out.println(dateFormat.format(date)+ " => Random no " + randomInt);
session.insert(emp);
session.fireAllRules();
}
} catch (Exception e) {
e.printStackTrace();
}finally {
session.dispose();
}
}
/**
* Create new knowledge base
*/
private static KnowledgeBase createKnowledgeBase() {
KnowledgeBuilder builder = KnowledgeBuilderFactory.newKnowledgeBuilder();
//Add drl file into builder
File drl = new File("D:\\eclipse\\worspace\\Research\\misc\\testforall.drl");
builder.add(ResourceFactory.newFileResource(drl), ResourceType.DRL);
if (builder.hasErrors()) {
System.out.println(builder.getErrors().toString());
//throw new RuntimeException(builder.getErrors().toString());
}
KnowledgeBase knowledgeBase = KnowledgeBaseFactory.newKnowledgeBase();
//Add to Knowledge Base packages from the builder which are actually the rules from the drl file.
knowledgeBase.addKnowledgePackages(builder.getKnowledgePackages());
KnowledgeBaseConfiguration config = KnowledgeBaseFactory.newKnowledgeBaseConfiguration();
config.setOption( EventProcessingOption.STREAM );
return knowledgeBase;
}
}
public class Employee {
private String Name;
private int Age;
// getter - setters
}

Answer 1

did you check the Drools Fusion documentation?
First of all, Employee doesn't sounds as a good idea for an Event. Events are meaningful changes of states of something related with your domain. So, an event could be the time of arrival of an Employee to the office, or the time of departure, but the Employee itself is a domain entity (or a fact for the rule engine) more than an event.
If you are interested in using Drools fusion temporal operators I recommend you to read about sliding windows (temporal ones) which will allow you to see what happen in the last ten seconds all the time. You don't need to use timers for that.
Cheers

Answer 2

You forgot telling what happened when you ran it, if you did.
If your entities set is not very large, I think this problem can be solved very easily with the base Drools distribution.
I have a similar app to yours and works for me:
rule "Clear only auxiliar fact"
salience 1
when
af: AuxFact()
then
DroolsRepository.retractFact(af);
end
rule "Clear auxiliar fact and an old meaningful fact"
salience 1000
when
af: AuxFact()
mf: MeaningfulFact()
then
if(DroolsRepository.getCurrentTimeMillis() - tmf.getCreationDate().getTime() > 5000){
DroolsRepository.retractFact(af);
DroolsRepository.retractFact(mf);
// YOUR MEANINGFUL CODE
}
else{
DroolsRepository.retractFact(af);}
end
query "getAllFacts"
$result: Fact()
end
and
// Boot rules re-executing thread.
new Thread(new Runnable(){
public void run(){
do{
kSession.insert(new AuxFact());
try{
Thread.sleep(99);}
catch(InterruptedException e){
e.printStackTrace();}}
while(true);}
}).start();
A similar approach could be simpler and effective.