[rules-users] Retraction of facts based on time - any ideas please?

Sat May 2 18:09:14 EDT 2009

If you can use Drools 5, then try out event expiration in stream mode using drools fusion:

https://hudson.jboss.org/hudson/job/drools/lastSuccessfulBuild/artifact/trunk/target/docs/drools-fusion/html_single/index.html#d0e1086

If you can't do that, you'll need an extra control object that's inserted periodically.  Let's call it Heartbeat: `

rule "Retract expired facts"
  dialect"mvel"
  // salience -5
  when
    h : Heartbeat();
    e1 : Event (code == "LOGON", status == "ACTIVE")
      eval ((h.getLongTimeStamp() - e1.getLongTimeStamp()) > 100)
  then
    System.out.println( "Retracting expired event with Timestamp: " + e1.longTimeStamp );
    retract (e1);
end

And you'll require an extra rule to cleanup the Heartbeat.  It should be lower priority than all other retract rules:

rule "Retract heartbeat"
  salience -1000
  when
    h : Heartbeat();
  then 
    retract(h);
end

Finally, you'll have to set up a java.util.Timer or a java.util.concurrent.ScheduledExecutorService to periodically insert a new Heartbeat into working memory.

Again, Drools 5 fusion handles all of this.  All you do is declare an object as an event, then define it's expiration time.

--- On Thu, 4/30/09, rsundaar at aretus.biz <rsundaar at aretus.biz> wrote:

> From: rsundaar at aretus.biz <rsundaar at aretus.biz>
> Subject: [rules-users] Retraction of facts based on time - any ideas please?
> To: "Rules Users List" <rules-users at lists.jboss.org>
> Date: Thursday, April 30, 2009, 5:38 AM
> <div id=yiv198814342><html><span
> style="font-family:Verdana;color:#000000;font-size:10pt;"><div> </div>
> <div>I have a need to "expire" some facts
> based on time. In other words, if an event occurs some time
> and if sufficient time has gone by, the fact should become
> inonsequential and be retracted. Here is my simple rule to
> do this:</div>
> <div> </div><font
> size="2">
> <div
> align="left"></font><b><font
> color="#960000" size="2"><font
> color="#960000"
> size="2"></b></font></font><font
> size="2"><font
> size="2"></div>
> <div
> align="left"></font><b><font
> color="#960000" size="2"><font
> color="#960000"
> size="2">rule</b></font></font><font
> size="2"></font><font
> color="#008000" size="2"><font
> color="#008000"
> size="2">"Retract expired
> facts"</div>
> <div
> align="left"></font></font><font
> size="2"></div>
> <div
> align="left"></font><b><font
> color="#960000" size="2"><font
> color="#960000"
> size="2">dialect</b></font></font><font
> size="2"></font><font
> color="#008000" size="2"><font
> color="#008000"
> size="2">"mvel"</div>
> <div
> align="left"></font></font><font
> size="2"></div>
> <div align="left"></font><font
> color="#808000" size="2"><font
> color="#808000" size="2">// salience
> -5</div>
> <div
> align="left"></font></font><font
> size="2"></div>
> <div
> align="left"></font><b><font
> color="#960000" size="2"><font
> color="#960000"
> size="2">when</div>
> <div
> align="left"></b></font></font><font
> size="2"></div>
> <div align="left">e1 : Event (code ==
> </font><font color="#008000"
> size="2"><font color="#008000"
> size="2">"LOGON"</font></font><font
> size="2">, status == </font><font
> color="#008000" size="2"><font
> color="#008000"
> size="2">"ACTIVE"</font></font><font
> size="2">)</div>
> <div
> align="left"></font><b><font
> color="#960000" size="2"><font
> color="#960000"
> size="2">eval</b></font></font><font
> size="2"> ((getCurrentTimeStamp ()-
> e1.getLongTimeStamp()) > </font><font
> size="2">100)</font><font
> size="2"></div>
> <div
> align="left"></font><b><font
> color="#960000" size="2"><font
> color="#960000"
> size="2">then</b></font></font><font
> size="2"></div>
> <div align="left">System.out.println(
> </font><font color="#008000"
> size="2"><font color="#008000"
> size="2">"Retracting expired event with
> Timestamp: "</font></font><font
> size="2"> + e1.longTimeStamp ); </div>
> <div
> align="left"></font><b><font
> color="#960000" size="2"><font
> color="#960000"
> size="2">retract</b></font></font><font
> size="2"> (e1);</div>
> <div align="left">
> <div align="left"></div>
> <div align="left"></font><font
> color="#960000" size="2"><font
> color="#960000" size="2"></div>
> <div><strong>end</strong></div>
> <div> </div>
> <div><font color="#000000">This does
> not seem to work because the "eval" method does
> not evaluate the rule every cycle. And, there is no other
> change to the fact (event) to force the rule to re-evaluate
> the fact. Is there a way to make "eval" in the LHS
> evaluate every cycle? Is there any other
> method?</font></div>
> <div><font
> color="#000000"></font> </div>
> <div><font color="#000000">I would
> greatly appreciate any ideas.</font></div>
> <div> </div>
> <div><font
> color="#000000">Thanks,</font></div>
> <p><font
> color="#000000">Ravi.</font></font></font><font
> size="2"></div></font></font></span></html>
> 
> </div>_______________________________________________
> rules-users mailing list
> rules-users at lists.jboss.org
> https://lists.jboss.org/mailman/listinfo/rules-users