[rules-users] Deadlock using BatchExecutionCommand and Rule that uses the duration attribute

[MacDonald, Bob]

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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