[rules-users] Garbage collection and sliding windows (Drools 5.5.0 Final)

[marianbuenosayres]

Could this be related to the issue at
https://issues.jboss.org/browse/JBRULES-3721? It started with performance
issues but eventually led to this case where a NPE is thrown by the
expire/retract action. They seem quite similar and perhaps the issue
attached project could help solve this issue as well.


laune wrote
> The original post mentioned "performance tests with Drools Fusion" in
> combination with using the feature of automatic event retraction. I
> don't think that OutOfMemory problems in this kind of scenario are due
> to some bug in Drools (Fusion) - at least not until I see a complete
> test app that reproduces the claimed problem.
> 
> It's important to note that automatic event retraction incurs a
> considerable overhead in addition to the work required for getting the
> event fact off the Rete
> network. Essentially, a "Job" (i.e., the retraction) is scheduled for
> punctual execution using a TimerService. One must therefore take care
> that the system can cope with the additional work of disbanding all of
> this contraband - otherwise it'll just clog, and croak.
> 
> Running fireUntilHalt() in one thread while inserting events from
> another one and expecting automatic event retraction to happen after
> 10s (due to a window:time(10s)) is one way of risking that the system
> runs into overload. With time slices being allotted equably to
> threads, a backlog will accumulate if the expire/retract takes longer
> than the insert/start-timer.
> 
> I've run the aforementioned scenario with System.sleep(nms) after
> every so many insertions, and this keeps the system in balance.
> Reducing nms gradually will - eventually - stress the system beyond
> its breaking point, and OutOfMemory occurs. (To fill up memory more
> quickly, the Event class was stuffed with some "dead data" -
> char[2000].)
> 
> -W
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