[rules-users] 5.6.0.CR1 gives a NullPointerException in after evaluator

Thu Nov 21 07:42:13 EST 2013

Actually one more observation. If I change the salience of the rule doing the modify so that the consequence executes before any other rules that match on that event/fact, then the NPE goes away for the exact same series of events.

Sent from my iPhone

> On Nov 21, 2013, at 7:14 AM, Jonathan Knehr <jonathan.knehr at gmail.com> wrote:
> 
> Unfortunately I was never able to reproduce this in a self-contained test. Currently, I have about 100 rules and I can't figure out what combination of events are causing it. Instead, I tried to clean up the symptoms of the issue by overriding the classes that were throwing the uncaught NPE and handling it properly with a logged error message. Interestingly enough, it doesn't seem to affect functionality once it is caught properly, at least that I can tell.
> 
> Some observations, though:
> - I have equality assertion type turned on
> - many if my events/facts are declared in the rules and are not pojos.
> - it has to do with modify/updates from rule consequences.
> - if I replace all of my modify's with a retract + copy over to new object + insert, then the issues seems to either go away or become less frequent.
> - annotating objects with the property reactive annotation makes it happen much, much less frequently
> - on an unrelated note, there is a race condition in the JIT compilation. If a fact is retracted at just the right time, it throws a NPE during the jitting process.
> 
> Sent from my iPhone
> 
>> On Nov 20, 2013, at 11:41 AM, Davide Sottara <dsotty at gmail.com> wrote:
>> 
>> Jonathan,
>> thanks for the hints. This seems to be a critical bug, could you please
>> provide some additional details
>> or, ideally, the unit test that you are running?
>> It would be really appreciated
>> Thanks
>> Davide
>> 
>>> On 11/18/2013 04:28 PM, Jonathan Knehr wrote:
>>> I only use it from a single thread. What I meant was that for example, for the same set of rules, the issue never was created with, say, 20 iterations of inserting the same facts/events over again. Instead, it was more on the order of a few hundred thousand before the NPEs started showing up. Literally running the same unit test in a loop until it NPE'ed. But all from a single thread...
>>> 
>>> Sent from my iPhone
>>> 
>>>> On Nov 18, 2013, at 4:00 PM, Davide Sottara <dsotty at gmail.com> wrote:
>>>> 
>>>> Jonathan,
>>>> Drools 5.5 was never meant to be multi-threaded. 5.6 tries to put a few
>>>> patches here and there, 6.0 is going in that direction and 6.1 will
>>>> hopefully solve the problem.
>>>> Thanks for the hint to the "internal hash table", it may give us ideas
>>>> on what to test next. However, if you or anyone could ever reproduce the
>>>> issue and submit a test
>>>> case that would be REALLY appreciated
>>>> Thanks
>>>> Davide
>>>> 
>>>>> On 11/18/2013 12:04 PM, Jonathan Knehr wrote:
>>>>> In the past I've tried to reproduce a similar issue.
>>>>> 
>>>>> Don't know if this will help, but I could not reproduce the NPEs without running a large amount of events into the rule engine. A small unit test never reproduced these issues for me, which made it harder. Not sure about this issue in particular, but other ones I've seen seem to be related to the internal hash table eventually misplacing objects. This created all sorts of odd symptoms, namely NPEs all over the place in random drools classes. But I think all of these are just symptoms of the same bug at the core level somewhere. They all are related IMO.
>>>>> 
>>>>> Sent from my iPhone
>>>>> 
>>>>>> On Nov 18, 2013, at 9:48 AM, Davide Sottara <dsotty at gmail.com> wrote:
>>>>>> 
>>>>>> I tried to reproduce the problem, with no success.
>>>>>> Could you please create a self-contained unit test?
>>>>>> If confirmed, I'll fix the problem as soon as possible
>>>>>> Thanks
>>>>>> Davide
>>>>>> 
>>>>>>> On 11/14/2013 04:48 AM, abr wrote:
>>>>>>> Hi everyone,
>>>>>>> 
>>>>>>> I tried to switch from 5.5.0.Final to 5.6.0.CR1 and got a null pointer
>>>>>>> exception in the evaluation of the after evaluator.
>>>>>>> (Exact method is:
>>>>>>> /org.drools.base.evaluators.AfterEvaluatorDefinition.AfterEvaluator.evaluate(InternalWorkingMemory,
>>>>>>> InternalReadAccessor, InternalFactHandle, InternalReadAccessor,
>>>>>>> InternalFactHandle)/ )
>>>>>>> 
>>>>>>> When debugging, the exception occurs at the very first line of the method,
>>>>>>> in:
>>>>>>> /    if ( extractor1.isNullValue( workingMemory, handle1.getObject() ) || 
>>>>>>>         extractor2.isNullValue( workingMemory, handle2.getObject() ) ) {
>>>>>>>     return false;
>>>>>>> }
>>>>>>> /
>>>>>>> The cause of the exception is that handle1 is null.
>>>>>>> 
>>>>>>> The rule where the exception occurs looks like:
>>>>>>> /    MyFact(
>>>>>>>     fromdate before[ 0d ] $min,
>>>>>>>     ( todate == null || todate after[ 0d ] $max ) )
>>>>>>> /
>>>>>>> 
>>>>>>> When the exception occurs, /MyFact.fromdate/ is not null, /$min/ is not
>>>>>>> null, /MyFact.todate/ is null, /$max/ is not null.
>>>>>>> In AfterEvaluator.evaluate : /extractor1/ refers to /MyFact.todate/,
>>>>>>> /extractor2/ refers to /$max/, /handle1/ is null, /handle2/ refers to the
>>>>>>> fact including the attribute to which /$max/ variable is bound to.
>>>>>>> 
>>>>>>> Of course, this worked fine in 5.5.0.Final.
>>>>>>> I couldn't test this out in Drools 6.0.0.CR5 because I have dependencies to
>>>>>>> drools-spring JAR that does not exist anymore in 6.0.0.CR5.
>>>>>>> 
>>>>>>> Is it simple to fix this problem?
>>>>>>> 
>>>>>>> Thanks in advance.
>>>>>>> 
>>>>>>> Best,
>>>>>>> Alexis
>>>>>>> 
>>>>>>> 
>>>>>>> 
>>>>>>> --
>>>>>>> View this message in context: http://drools.46999.n3.nabble.com/5-6-0-CR1-gives-a-NullPointerException-in-after-evaluator-tp4026780.html
>>>>>>> Sent from the Drools: User forum mailing list archive at Nabble.com.
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