[rules-users] Monitoring applications using Drools
Sushant Goyal
sushantgoyal25 at yahoo.co.in
Thu Jun 5 04:09:49 EDT 2014
I found one of the explanations on how Sliding Windows
operate in Drools while searching for an answer:
“Events are expired
from the time window when the clock advances”
So, in my case if I am inserting events on T0 (insert 1st event), T1 (insert 2nd event), T2 (insert 3rd event) and
advancing the clock to T3, T4 and T5; 1st event inserted at T0 is
expired from the window. And the rule calculates the average of the last two
events (2nd event & 3rd event) falling in the time
window. And the output average calculated by the from accumulate function comes
to be (26 +28 / 2 == 27) satisfying the contract of average temperature to be above
the threshold value of 25.
Now let’s say I do the below (advancing the clock by 5
minutes after the 3rd insert):
T0 (insert 1st event)
T1 (insert 2st event)
T2 (insert 3st event)
T3
T4
T5
T6
T7
Fire all rules
The average calculated by the rule is zero (0) since the
three inserted events fall outside the time window of 5 minutes (as expected).
But, my rule fires regardless of the fact I have the contract of average temperature
to be greater than threshold in my rule :
$averageTemp : Number(intValue
> 25)
from accumulate(SensorReading($temp : temperature)
over window:time(5m) from
entry-point "Temperature Reading", average($temp))
As per the drools-fusion documentation, over window : time(X) is used to consider events that happened in
the last X units. So, is there something that needs to be changed in my rule
implementation?
One more question here, does over window : time(X) really considers events occurred in the last
X units. I tried going further by doing the below:
T0 (insert 1st event – Sensor reading is 24)
T1 (insert 2st event – Sensor reading is 26)
T2 (insert 3st event – Sensor reading is 28)
T3
T4
T5
T6
T7
(insert event – Sensor reading is 30)
Fire All rules
With the above test setup, my rule gets invoked twice printing
the average of temperatures as (30) and (30). But using over window:time(5m) shouldn’t result in rule being triggered once ?
Thanks in advance!
On Thursday, 5 June 2014 1:35 PM, Sushant Goyal <sushantgoyal25 at yahoo.co.in> wrote:
Thanks again for your response Wolfgang.
I found one of the explanations on how Sliding Windows
operate in Drools while searching for an answer:
“Events are expired
from the time window when the clock advances”
So, in my case if I am inserting events on T0 (insert 1st event), T1 (insert 2nd event), T2 (insert 3rd event) and
advancing the clock to T3, T4 and T5; 1st event inserted at T0 is
expired from the window. And the rule calculates the average of the last two
events (2nd event & 3rd event) falling in the time
window. And the output average calculated by the from accumulate function comes
to be (26 +28 / 2 == 27) satisfying the contract of average temperature to be above
the threshold value of 25.
Now let’s say I do the below (advancing the clock by 5
minutes after the 3rd insert):
T0 (insert 1st event)
T1 (insert 2st event)
T2 (insert 3st event)
T3
T4
T5
T6
T7
Fire all rules
The average calculated by the rule is zero (0) since the
three inserted events fall outside the time window of 5 minutes (as expected).
But, my rule fires regardless of the fact I have the contract of average temperature
to be greater than threshold in my rule :
$averageTemp : Number(intValue
> 25)
from accumulate(SensorReading($temp : temperature)
over window:time(5m) from
entry-point "Temperature Reading", average($temp))
As per the drools-fusion documentation, over window : time(X) is used to consider events that happened in
the last X units. So, is there something that needs to be changed in my rule
implementation?
One more question here, does over window : time(X) really considers events occurred in the last
X units. I tried going further by doing the below:
T0 (insert 1st event – Sensor reading is 24)
T1 (insert 2st event – Sensor reading is 26)
T2 (insert 3st event – Sensor reading is 28)
T3
T4
T5
T6
T7
(insert event – Sensor reading is 30)
Fire All rules
With the above test setup, my rule gets invoked twice printing
the average of temperatures as (30) and (30). But using over window:time(5m) shouldn’t result in rule being triggered once ?
Thanks in advance!
On Thursday, 5 June 2014 12:31 PM, Wolfgang Laun <wolfgang.laun at gmail.com> wrote:
Computations involving intervals where events arrive in real time
should not depend on differences of one unit of the smalles unit of
time for specifying durations (here: milliseconds).
-W
On 04/06/2014, Sushant Goyal <sushantgoyal25 at yahoo.co.in> wrote:
> 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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