[rules-users] Event expiration doubt

[Makewise - Vitor Rui Mendonça]

Hi!

 

I've detected some problems in my rules regarding event expiration but I can't understand why. Maybe someone with more experience could help me out.

 

I think the example is quite simple: the application receives transactions. The lack of transactions for an hour should raise an alarm. If there's a transaction when the alarm is on, then the application should rearm, clear the alarm state and check for lack of transactions.

 

The rules:

package com.company.application;

 

import com.company.application.Notifier;

import com.company.application.Notification;

import com.company.application.Transaction;

 

dialect "java"

 

# event which represents an alarm state

declare NoTransactions

      @role( event )

      dummy1: long

end

 

# event which represents the start of drools engine

declare EngineStarted

      @role( event )

      dummy2 : long

end

 

# event which represents the need to check for absence of transactions for the first hour

declare CheckFirstTransaction

      @role( event )

      @expire( 1h )

      dummy3: long

end

 

# event which represents a Transaction

declare Transaction

      @role( event )

      @expires( 1h )

end

 

# Notification System

global Notifier notifier;

 

 

rule "***start***"

when

      not( EngineStarted() )

then

      insert( new EngineStarted() );

      insert( new CheckFirstTransaction() );

end

 

 

rule "***notrx_after_start***"

when

      $engineStarted : EngineStarted()

      $checkFirstTransaction : CheckFirstTransaction() 

      not( NoTransactions() )

      not( Transaction( this after[0s,1h] $engineStarted ) from entry-point "incoming" ) 

then

      insert ( new NoTransactions() );

      retract( $checkFirstTransaction );

      notifier.send( new Notification( "ALARM" ) );

end

 

 

rule "***notrx_after_trx***"

when

      EngineStarted()

      not( NoTransactions() )

      $transaction: Transaction() from entry-point "incoming"

      not( Transaction( this != $transaction, this after [0s,1h] $transaction ) from entry-point "incoming" ) 

then

      insert( new NoTransactions());

      notifier.send( new Notification( "ALARM" ) );

end

 

 

rule "***rearm***"

when

      EngineStarted()

      $noTransactions : NoTransactions()

      $transaction: Transaction( this after $noTransactions ) from entry-point "incoming"

then

      retract( $noTransactions );

      notifier.send( new Notification( "REARM" ) );

end

 

 

The unit test:

kSession.fireAllRules(); // needed to detect lack of transactions in the first hour

 

/* here, "***start***" rule fires => "EngineStarted" and "CheckFirstTransaction" inserted */

 

clock.advanceTime( 1, TimeUnit.HOURS );

 

/* here, "***notrx_after_start***" rule fires => "NoTransactions" inserted, "CheckFirstTransaction" retracted */

 

clock.advanceTime(10, TimeUnit.MINUTES );

 

entryPoint.insert( new Transaction() );

 

/* before inserting "Transaction" into EntryPoint, "NoTransactions" is retracted */

 

kSession.fireAllRules();

 

 

The problem:

After inserting the last transaction, automatically the NoTransactions event is retracted. Debugging inside drools-core project, I've discovered that the event was retracted because expiration (WorkingMemoryReteExpireAction on actionQueue). 

I've also found some more explain how expiration events works, by Edison (http://drools-java-rules-engine.46999.n3.nabble.com/Events-are-not-automatically-expiring-from-working-memory-td61127.html). That shed some light on *when* the event is retracted but I don't understand *why* it's retracted.

 

 

Thanks In Advance!

 

 

Vítor Mendonça Moreira
Analista / Programador
Direcção de Investigação e Desenvolvimento

Rua Dr. Francisco Sá Carneiro, nº. 4 r/c esq.
2500 - 206 - Caldas da Rainha
Tel: (+351) 262 832 196
Fax: (+351) 262 186 455
Web: www.makewise.pt <http://www.makewise.pt> 
Uma empresa: Grupo Sousa Pedro <http://www.sousapedro.com>  

 

		

 

 

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