[rules-users] Consequence Exception with too many events

[Jason Barto]

Wolfgang,
I'd agree with you although I will continue to research further.  If it is
as you suggest - a race condition - I would think a more appropriate
reaction of the system would be to emit a warning that events are expiring
before they can be considered by the rules engine, although I would think
that this is a use case which does not see much real life execution.  Thank
you very much for your time and input into this matter, it's been
educational.

Sincerely,
Jason

On Saturday, May 4, 2013, Wolfgang Laun wrote:

> I can confirm that (using 5.5.0) this NPE occurs predictably with a
> limit of 500000.
>
> It looks like a race condition to me - at least that is what line
> DefaultAgenda.java:1319 suggests. Possibly it is due to automatic
> retraction "overtaking" rule firing, since the latter tends to take
> much, much longer than the ~10sec the mere insertion of 500K events
> takes on my system.
>
> 500,000 inserted in 10s means 50,000/s, and that, in turn, implies
> 50,000 retractions per second.  30s after the last insertion, only
> ~90,000 firings have taken place. (I added a printout of the counter's
> total after the Thread.sleep().)
>
> It's interesting to experiment with the @expires value: Everything
> else remaining the same, a setting of @expires(10s) will let the
> firings complete without a NPE.
>
> So, I'm back to my surmise: a race condition, due to expiry being cut
> too short to cope with the system load. I'd still classify this as a
> Drools bug: it should notice that it is being overtaxed and/or
> destabilizing itself.
>
> -W
>
>
> On 04/05/2013, Jason Barto <jason.p.barto at gmail.com> wrote:
> > Wolfgang,
> > thank you for your prompt reply.  After further work with my code I think
> > the culprit may have either been the setting of the event expiration time
> > to 1s OR that I was using session.update to insert a new counter object;
> > but maybe not.  I cleaned up my code in order to send it out.  In doing
> so
> > I also downloaded the official Drools 5.5 distribution (in the previous
> > example I was using the libraries packaged with BRMS).  Between the code
> > cleanup and the use of the official distro I'm no longer experiencing a
> > Consequence Exception.
> >
> > That being said I am still experiencing a NPE when a high iteration
> count.
> > If you take a look at Drools5FusionEval.java, around line 51 you'll see a
> > variable 'eventLimit'.  If set to 500000 it seems to pretty reliably kick
> > out the following NPE:
> >
> > Exception in thread "Thread-1" java.lang.NullPointerException
> >     at
> > org.drools.common.DefaultAgenda.fireActivation(DefaultAgenda.java:1319)
> >     at
> > org.drools.common.DefaultAgenda.fireNextItem(DefaultAgenda.java:1221)
> >     at
> > org.drools.common.DefaultAgenda.fireUntilHalt(DefaultAgenda.java:1434)
> >     at
> >
> org.drools.common.AbstractWorkingMemory.fireUntilHalt(AbstractWorkingMemory.java:755)
> >     at
> >
> org.drools.common.AbstractWorkingMemory.fireUntilHalt(AbstractWorkingMemory.java:731)
> >     at
> >
> org.drools.impl.StatefulKnowledgeSessionImpl.fireUntilHalt(StatefulKnowledgeSessionImpl.java:247)
> >     at
> drools5fusioneval.Drools5FusionEval$1.run(Drools5FusionEval.java:47)
> >
> > As I've said I'm still very new to Drools and trying to understand better
> > how it does what it does - any information that anyone can provide to
> help
> > me understand why the above error is being experienced would be greatly
> > appreciated.
> >
> > Source code and rules are attached.
> >
> > Sincerely,
> > Jason
> >
> >
> > On Sat, May 4, 2013 at 7:58 AM, Wolfgang Laun
> > <wolfgang.laun at gmail.com>wrote:
> >
> >> Works for me (5.5.0, 5.4.0) - at least based on the code you've posted
> >> which (apart from the omitted getters and setters) isn't the one you've
> >> been running, and so you may have changed or omitted something
> >> that's essential.
> >>
> >> The full stack dump might shed some more light on this, and the full and
> >> true code of the rule RHS whre the NPE is caused.
> >>
> >> -W
> >>
> >> On 04/05/2013, Jason Barto <jason.p.barto at gmail.com> wrote:
> >> > I am new to Drools (Expert and Fusion) and have been reading through
> >> > the
> >> > materials over the last few days.  After going through some of the
> >> tutorial
> >> > code I wrote a very quick and dirty to perform a base assessment of
> the
> >> > speed of Fusion / Expert.  My code is below.  The strange thing I'm
> >> > currently receiving is, if I insert 100k events the test completes
> >> > successfully, if I insert 150k events, I receive a
> ConsequenceException
> >> > caused by an NPE.  Being new to Drools I must be doing something
> wrong,
> >> can
> >> > anyone please provide some guidance?
> >> >
> >> > (Main function)
> >> > Counter cc = new Counter ();
> >> > session.insert (cc);
> >> > for (int i = 0; i < 150000; i++) {
> >> >   entryPoint01.insert (new MyEvent ());
> >> > }
> >> >
> >> > (Counter Class)
> >> > public class Counter {
> >> >   private long total = 0;
> >> >   // get / set total
> >> >   public void addValue (int val) {
> >> >     total += val;
> >> >   }
> >> > }
> >> >
> >> > (MyEvent Class)
> >> > public class MyEvent {
> >> >   private int value = 1;
> >> >   // get / set value
> >> > }
>
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