[rules-users] Monitoring applications using Drools
Sushant Goyal
sushantgoyal25 at yahoo.co.in
Wed Jun 4 17:07:54 EDT 2014
Thanks for your response.
I was under the assumption that the window time frame begins, the moment first event is inserted into the working memory. Or I am still missing out something here (when you say that the first event is exactly at the beginning of the window)? If I traverse backwards as below, then definitely the 1st event lies outside the window.
insert 1st event
delay 1 minute ^ (4 + 1 = 5)
insert 2nd event
delay 1 minute ^ (3 + 1 = 4)
insert 3rd event
delay 1 minute ^ (2 + 1 = 3)
delay 2 minutes ^
fire all rules
However, if I start from the 1st event, the possibility where 1st event lies out of time frame of 5 mins would be if certain amount of time is consumed while inserting the 1st event. I tried to check it programmatically to see if there is any time lapsed during the insertion of the event by printing the clock's current time using clock.getCurrentTime() method before and after inserting the 1st event, however, could not notice any difference.
But, if I change the time to be advanced by 1 minutes and 59 seconds (instead of 2 minutes) towards the end after the three events have been inserted, the rule seems to be working fine by considering all the three events for calculating the average.
I know I am definitely missing out something here as I can see the difference in the behavior of the rule by merely reducing the total delay in time by 1 second (4 min 59 sec instead of 5 minutes) as stated above. But I am not able to figure that out.
Could you please provide more insight.
Thanks!
On Wednesday, 4 June 2014 9:01 PM, Wolfgang Laun <wolfgang.laun at gmail.com> wrote:
Your code does:
insert 1st event
delay 1 minute
insert 2nd event
delay 1 minute
insert 3rd event
delay 1 minute
delay (1 or) 2 minutes
fire all rules
In the second case, 5 minutes have elapsed since the 1st insert. I
don't think that this means "that [the 1st insert] falls well within
the specified time range" - it is exactly at the beginning of the
window, and I'd expect the window to be an interval open at one end -
otherwise events smack on the point in time "separating" two intervals
would be in both windows.
-W
On 04/06/2014, Sushant Goyal <sushantgoyal25 at yahoo.co.in> wrote:
> Hi,
>
> I am
> trying to understand how Drools can be used to monitor events over a period
> of
> time using Sliding Time Windows. I have created a rule to sound an alarm
> when
> average temperature read from a sensor is above 25 degrees (threshold) over
> a
> time period of 5 minutes. The rule makes of use of the Stream processing
> mode so
> that continuous stream of events could be processed.
>
> Below
> is how my rule looks like:
>
> //declare any global
> variables here
> globaljava.lang.StringBuilder alertMessage
>
> // add declaration to
> change the Fact into an Event
> declareSensorReading
> @role(event)
> end
>
> /* Alert when average
> temperature is above 25
> over a time period of 5 minutes */
> rule"TemperatureAlarm1"
>
> when
> //conditions
> $averageTemp : Number(doubleValue >
> 25.00)
> fromaccumulate(SensorReading($temp
> : temperature)
> over
> window:time(5m) fromentry-point "Temperature Reading", average($temp))
> then
> //actions
> System.out.println("Fired rule:
> "+
> kcontext.getRule().getName());
> alertMessage.append("Threshold
> temperature breached!!"+
> "\nTurn on the
> Air Conditioner"+
> "\nAverage
> temperature over 5 minutes is above 25 ("+ $averageTemp.intValue() + ")\n");
>
> end
>
> And below
> is the snapshot of the fact (SensorReading) which is inserted as an event in
> the working memory:
>
> publicclassSensorReading {
>
> privatedoubletemperature;
>
> publicSensorReading(){}
>
> publicSensorReading(doubletemp){
> this.temperature= temp;
> }
>
> // getters and setters
> }
>
>
> In
> order to test the rule, I am using Pseudo Clock with Stream processing
> turned
> on. I am inserting three SensorReading objects in the working memory with
> temperature
> values as (24, 26, 28) after every minute, so that the average of the
> temperatures is above threshold and the rule is invoked. After the objects
> are
> inserted in the working memory, I am deliberately advancing the Pseudo clock
> by
> another 1 minute, so that the total time elapsed is 4 minutes. The rule
> works
> as expected with the above test setup and prints the average value as 26 on
> the
> console.
>
> However,
> if I advance the clock by 2 minutes instead of 1 minute after three sensor
> reading objects have been inserted in the working memory (after every 1
> minute
> interval), the rule gets invoked but the average value gets changed to 27
> (26 +
> 28 / 2 == 27). Looks like the first temperature reading is getting ignored
> by
> the rule despite the fact that it falls well within the specified time range
> of
> 5 minutes. Below is the snapshot of my test class:
>
> publicclassTemperatureAlarmTest
> {
>
> staticKnowledgeBase kbase;
> staticStatefulKnowledgeSession ksession;
> staticKnowledgeRuntimeLogger logger;
> staticSessionPseudoClock clock;
>
> @BeforeClass
> publicstaticvoidsetupKsession() {
> try{
> // load up the
> knowledge base
> kbase= readKnowledgeBase();
> ksession= readKnowldedeSession(kbase);
> clock= ksession.getSessionClock();
>
> logger=
> KnowledgeRuntimeLoggerFactory.newThreadedFileLogger(ksession, "log/Errors",
> 500);
>
> } catch(Throwable t) {
> t.printStackTrace();
> }
> }
>
> /**
> *
> Create a new Stateful knowledge Session with a pseudo clock from the
> *
> knowledge base
> *
> * @paramkbase
> * @return
> * @throwsException
> */
> privatestaticStatefulKnowledgeSession readKnowldedeSession(
> KnowledgeBase kbase) throwsException {
>
> // Knowledge Session Configuration
> KnowledgeSessionConfiguration
> config = KnowledgeBaseFactory.newKnowledgeSessionConfiguration();
> config.setOption(ClockTypeOption.get("pseudo"));
> returnkbase.newStatefulKnowledgeSession(config, null);
>
> }
>
> @AfterClass
> publicstaticvoidcloseKsession() {
> try{
> // load up the
> knowledge base
> logger.close();
> ksession.dispose();
>
> } catch(Throwable t) {
> t.printStackTrace();
> }
> }
>
> @Test
> publicvoidTemperatureAlarm1_Test() {
>
> // Create Temperature list
> ArrayList<SensorReading>
> tempMetrics = newArrayList<SensorReading>();
> doubletemp = 24.00;
>
> while(tempMetrics.size()
> < 3) {
> tempMetrics.add(newSensorReading(temp));
> temp += 2;
> }
> System.out.println("Size of
> tempMetrics List: "+tempMetrics.size()+"\n");
> System.out.println("First Temp
> reading: "+tempMetrics.get(0).getTemperature());
> System.out.println("Second Temp
> reading: "+tempMetrics.get(1).getTemperature());
> System.out.println("Third Temp
> reading: "+tempMetrics.get(2).getTemperature()+"\n");
>
> // Separate stream for inserts
> WorkingMemoryEntryPoint
> temperatureStream = ksession.getWorkingMemoryEntryPoint( "Temperature
> Reading");
>
> // Create fact handle list
> ArrayList<FactHandle>
> factHandleList = newArrayList<FactHandle>();
>
> // Insert objects into working
> memory while advancing the clock
> for(inti = 0; i <
> tempMetrics.size(); i++) {
>
> factHandleList.add(temperatureStream.insert(tempMetrics.get(i)));
> clock.advanceTime(1,
> TimeUnit.MINUTES);
> System.out.println("Time advances
> by 1 minute");
> }
> System.out.println("Fact Count
> is: "+temperatureStream.getFactCount());
> System.out.println("Fact Entry
> Point is: "+temperatureStream.getEntryPointId());
> System.out.println("Size of
> FactHandleList: "+factHandleList.size()+"\n");
>
> clock.advanceTime(1,
> TimeUnit.MINUTES); //change in
> advanced time alters the rule behavior
>
> StringBuilder stringBuilder = newStringBuilder();
> ksession.setGlobal("alertMessage", stringBuilder);
> ksession.fireAllRules();
>
> // Remove facts
> for(inti = 0; i <
> factHandleList.size(); i++) {
> temperatureStream.retract(factHandleList.get(i));
> }
> System.out.println("After
> Removing facts");
> System.out.println("Fact Count
> is: "+temperatureStream.getFactCount());
>
> String result =
> stringBuilder.substring(0, 32);
> System.out.println("Alert Message
> is: \n"+ stringBuilder.toString());
> assertEquals("Alert Message
> is: ", "Threshold
> temperature breached!!", result);
> }
>
> /**
> *
> Create the knowledge base with stream processing turned on.
> *
> * @return
> * @throwsException
> */
> privatestaticKnowledgeBase
> readKnowledgeBase() throwsException {
> KnowledgeBuilder kbuilder =
> KnowledgeBuilderFactory.newKnowledgeBuilder();
>
> kbuilder.add(ResourceFactory.newClassPathResource("TemperatureAlarm1.drl"),ResourceType.DRL);
> hasErrors(kbuilder);
>
> // Stream processing turned on
> KnowledgeBaseConfiguration conf =
> KnowledgeBaseFactory.newKnowledgeBaseConfiguration();
> conf.setOption(EventProcessingOption.STREAM);
> KnowledgeBase kbase =
> KnowledgeBaseFactory.newKnowledgeBase(conf);
> hasErrors(kbuilder);
> kbase.addKnowledgePackages(kbuilder.getKnowledgePackages());
>
> returnkbase;
> }
>
> /**
> *
> Report errors if any
> *
> * @paramkbuilder
> * @throwsException
> */
> privatestaticvoidhasErrors(KnowledgeBuilder kbuilder) throwsException
> {
> KnowledgeBuilderErrors errors =
> kbuilder.getErrors();
> if(errors.size() > 0) {
> for(KnowledgeBuilderError error : errors) {
> System.err.println(error);
> }
> thrownewIllegalArgumentException("Could not parse
> knowledge.");
> }
>
> }
>
> }
>
>
> Could
> anyone please help explain this change in the behavior of the rule?
>
> Regards,
> Sushant
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