[rules-users] GC Overhead Limit Exceeded and 1B JoinLeftNode Objects

[Mark Proctor]

On 19 Feb 2013, at 15:57, Julian Klein <julianklein at gmail.com> wrote:

> Ok, so I reviewed my code again and found a spot where I am queuing up tasks to process data that hadn't been loaded.  My application shouldn't spawn a rule sessions in the case.  I have also moved to a sever with less RAM and will begin profiling as soon as possible.   Here is where I stand as of now:
> 
> 1) I am still seeing about 250 million JoinNodeLeftTuples (eats up about 30GB of RAM).  This greatly outnumbers anything else in the system by a factor of 100x.
> 2) Creating a test case will be very difficult as I cannot pinpoint the root cause of this issue.  I am not sure if it is related to too many rules engine, the size of my ruleset, or simply the scale at which I am attempting to use Drools.  If I pinpoint an actual memory leak, I will create a test case and submit.
> 3) I cannot use a StatelessKnowledgeSession as it locks my process up.  It seems the code in StatelessKnowledgeSessionImpl's constructor creates a lock that never releases.  No idea on this either for now.
> 
>             this.ruleBase.lock();
>             try {
>                 if ( ruleBase.getConfiguration().isSequential() ) {
>                     this.ruleBase.getReteooBuilder().order();
>                 }
>             } finally {
>                 this.ruleBase.unlock();   <--- This line is never reached for some reason
>             }
>  
> I will continue trying to find a root cause or path forward and report back.  If anything here gives you all a sense of some wrongdoing on my behalf, please let me know.  I don't fully understand sequential mode as the documentation is not approachable from my uninformed perspective.  So perhaps there is something I am doing in my rules that leads to this lock not getting release?
Sequential mode means no inference. If you want to modify or insert facts and have them evaluated in the rules, then you don't want sequential mode.
> 
> Thanks again,
> Julian
> 
> 
> On Mon, Feb 18, 2013 at 9:13 AM, Julian Klein <julianklein at gmail.com> wrote:
> Unfortunately the server I was using locked up last night and I cannot get access.  I'll have to find an interim system where I can run tests and profile the heap.  In the meantime, I switched to a Sequential Stateless Session.  I don't know the internals of Drools, but since this seems to turn off the left input propagation, does that mean the JoinLeftNode is not used?
> 
> I am running 5.4 .0 on Linux.  If I see the same issues with a stateless approach, I will try the 5.5 approach.
> 
> Thanks again,
> Julian
> 
> 
> On Feb 17, 2013, at 6:19 PM, Mark Proctor <mproctor at codehaus.org> wrote:
> 
>> You'll need to help us a bit here, by creating a test of some sort. "I have 100 rules with 1B JoinLeftNode" doesn't give us much to go on.
>> 
>> The problem mentioned earlier was related to windows, which I don't think you are using - or you'd have said so.
>> 
>> Also can you tell us what version you are using? Could you maybe try the 5..5.x branch which has a lot of fixes in it (you'll need to build it with maven):
>> https://github.com/droolsjbpm/drools/tree/5.5.x
>> 
>> mark
>> On 17 Feb 2013, at 18:27, Julian Klein <julianklein at gmail.com> wrote:
>> 
>>> Thanks again. I have tried Sequential mode, but somehow my Java based class that I use for function calls no longer receives them.  Perhaps there is an error occurring before the call to my class in the "then" section of the rule that is not presenting itself in my logs.  Either that or I don't understand sequential mode's limitations well enough.  I'll try it one more time and report back on that as well.
>>> 
>>> 
>>> On Sun, Feb 17, 2013 at 1:17 PM, Wolfgang Laun <wolfgang.laun at gmail.com> wrote:
>>> On 17/02/2013, Julian Klein <julianklein at gmail.com> wrote:
>>> > Ok, I witnessed this with JProfiler.  I will try with jmap to make sure and
>>> > report back later today or tomorrow.   Is it safe then to assume that
>>> > discarding (dispose) the session between laps is better from a throughput
>>> > perspective than re-using it?
>>> 
>>> If you need to start each session with a clean slate: yes, dispose is
>>> preferable.
>>> 
>>> >  Also, would using a Stateless Session
>>> > "perform" better from either a memory or CPU perspective?
>>> 
>>> Only if you can run it in "sequential mode" - see Expert, 3.3.7.1.
>>> Sequential Mode
>>> 
>>> -W
>>> 
>>> >
>>> > Thanks again!
>>> >
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>> 
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