Has anyone run into this issue? I've found a couple other references to
deadlocks but nothing that seems to match exactly what I'm seeing. I'm
running with drools 5.1.1 and using the BatchExecutionCommand interface
to feed a set of commands into my StatefulKnowledgeSession. I also have
a simple rule that uses the duration attribute to clean up old facts.
The problem is that the thread that executes the rule associated with
the duration attribute acquires the lock associated with the
DefaultAgenda class object and subsequently tries to acquire the locks
managed by the AbstractWorkingMemory. However, my main thread that uses
the BatchExecutionCommand interface could run while the other thread is
running and this thread first acquires the AbstractWorkingMemory locks
and later tries to acquire the DefaultAgenda class object lock resulting
in the deadlock.
Here's is the stack trace for the thread that runs when duration
expires:
Unsafe.park(boolean, long) line: not available [native method]
LockSupport.park(Object) line: 158
ReentrantLock$NonfairSync(AbstractQueuedSynchronizer).parkAndCheckInterr
upt() line: 747
ReentrantLock$NonfairSync(AbstractQueuedSynchronizer).acquireQueued(Abst
ractQueuedSynchronizer$Node, int) line: 778
ReentrantLock$NonfairSync(AbstractQueuedSynchronizer).acquire(int) line:
1114
ReentrantLock$NonfairSync.lock() line: 186
ReentrantLock.lock() line: 262
ReteooStatefulSession(AbstractWorkingMemory).retract(FactHandle,
boolean, boolean, Rule, Activation) line: 1256
DefaultKnowledgeHelper.retract(FactHandle) line: 201
DefaultKnowledgeHelper.retract(Object) line: 214
Rule_Automatically_Remove_Old_Events_0.defaultConsequence(KnowledgeHelpe
r, Event, FactHandle) line: 10
Rule_Automatically_Remove_Old_Events_0DefaultConsequenceInvoker.evaluate
(KnowledgeHelper, WorkingMemory) line: 29
DefaultAgenda.fireActivation(Activation) line: 917
Scheduler$ActivationTimerJob.execute(JobContext) line: 73
JDKTimerService$JDKCallableJob.call() line: 147
JDKTimerService$JDKCallableJob.call() line: 125
FutureTask$Sync.innerRun() line: 303
ScheduledThreadPoolExecutor$ScheduledFutureTask<V>(FutureTask<V>).run()
line: 138
ScheduledThreadPoolExecutor$ScheduledFutureTask<V>.access$301(ScheduledT
hreadPoolExecutor$ScheduledFutureTask) line: 98
ScheduledThreadPoolExecutor$ScheduledFutureTask<V>.run() line: 207
ThreadPoolExecutor$Worker.runTask(Runnable) line: 886
ThreadPoolExecutor$Worker.run() line: 908
Thread.run() line: 619
And here's the stack trace of the thread using the BatchExecutionCommand
interface:
DefaultAgenda.fireActivation(Activation) line: 889
DefaultAgenda.fireNextItem(AgendaFilter) line: 856
DefaultAgenda.fireAllRules(AgendaFilter, int) line: 1071
ReteooStatefulSession(AbstractWorkingMemory).fireAllRules(AgendaFilter,
int) line: 785
ReteooStatefulSession(AbstractWorkingMemory).fireAllRules() line: 751
StatefulKnowledgeSessionImpl.fireAllRules() line: 218
FireAllRulesCommand.execute(Context) line: 99
FireAllRulesCommand.execute(Context) line: 33
BatchExecutionCommandImpl.execute(Context) line: 159
BatchExecutionCommandImpl.execute(Context) line: 81
StatefulKnowledgeSessionImpl.execute(Context, Command<T>) line: 887
StatefulKnowledgeSessionImpl.execute(Command<T>) line: 862
Rules$RuleRunnerThread.run() line: 554
The rule with the duration attribute is very simple and included below:
rule "Automatically Remove Old Events"
agenda-group "SYSTEM"
// 1 hour (specified in milliseconds)
duration 3600000
when
$event : Event(eventId : id)
not SituationEvent(correlator == eventId)
then
retract($event);
end
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