Running More Than 100 Threads Results in ArrayIndexOutOfBoundsException from Drools AbstractHashTable

Effected: Drools Flow and Drools Core
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Unfortunately it is not a consistent behaviour, but happens quite often.

java.util.concurrent.ExecutionException: org.drools.RuntimeDroolsException: Unexpected exception executing action org.drools.reteoo.ReteooWorkingMemory$WorkingMemoryReteAssertAction@1102fab
at java.util.concurrent.FutureTask$Sync.innerGet(FutureTask.java:222)
at java.util.concurrent.FutureTask.get(FutureTask.java:83)
at org.custom.workflow.stress.test.WorkflowStressTest.shouldRunFlow(WorkflowStressTest.java:50)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:44)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:41)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20)
at org.springframework.test.context.junit4.statements.RunBeforeTestMethodCallbacks.evaluate(RunBeforeTestMethodCallbacks.java:74)
at org.springframework.test.context.junit4.statements.RunAfterTestMethodCallbacks.evaluate(RunAfterTestMethodCallbacks.java:82)
at org.springframework.test.context.junit4.statements.SpringRepeat.evaluate(SpringRepeat.java:72)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:240)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:193)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:52)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:191)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:42)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:184)
at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)
at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:31)
at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:70)
at org.junit.runners.ParentRunner.run(ParentRunner.java:236)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:180)
at org.junit.runner.JUnitCore.run(JUnitCore.java:157)
at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:94)
at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:192)
at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:64)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:115)
Caused by: org.drools.RuntimeDroolsException: Unexpected exception executing action org.drools.reteoo.ReteooWorkingMemory$WorkingMemoryReteAssertAction@1102fab
at org.drools.common.AbstractWorkingMemory.executeQueuedActions(AbstractWorkingMemory.java:1473)
at org.drools.common.AbstractWorkingMemory.startProcess(AbstractWorkingMemory.java:1631)
at org.drools.impl.StatefulKnowledgeSessionImpl.startProcess(StatefulKnowledgeSessionImpl.java:318)
at org.drools.command.runtime.process.StartProcessCommand.execute(StartProcessCommand.java:99)
at org.drools.command.runtime.process.StartProcessCommand.execute(StartProcessCommand.java:38)
at org.drools.persistence.session.SingleSessionCommandService.execute(SingleSessionCommandService.java:285)
at org.drools.command.impl.CommandBasedStatefulKnowledgeSession.startProcess(CommandBasedStatefulKnowledgeSession.java:193)
at net.sf.cglib.proxy.MethodProxy.invoke(MethodProxy.java:191)
at org.springframework.aop.framework.Cglib2AopProxy$CglibMethodInvocation.invokeJoinpoint(Cglib2AopProxy.java:692)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:150)
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:110)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)
at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:89)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)
at org.springframework.aop.framework.Cglib2AopProxy$DynamicAdvisedInterceptor.intercept(Cglib2AopProxy.java:625)
at org.custom.workflow.stress.test.WorkflowRunner.call(WorkflowRunner.java:18)
at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303)
at java.util.concurrent.FutureTask.run(FutureTask.java:138)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
at java.lang.Thread.run(Thread.java:662)
Caused by: java.lang.ArrayIndexOutOfBoundsException: -1
at org.drools.core.util.AbstractHashTable$HashTableIterator.next(AbstractHashTable.java:317)
at org.drools.reteoo.EntryPointNode.updateSink(EntryPointNode.java:323)
at org.drools.reteoo.ObjectTypeNode.attach(ObjectTypeNode.java:303)
at org.drools.reteoo.builder.PatternBuilder.attachObjectTypeNode(PatternBuilder.java:257)
at org.drools.reteoo.ClassObjectTypeConf.<init>(ClassObjectTypeConf.java:92)
at org.drools.common.ObjectTypeConfigurationRegistry.getObjectTypeConf(ObjectTypeConfigurationRegistry.java:68)
at org.drools.reteoo.Rete.assertObject(Rete.java:111)
at org.drools.reteoo.ReteooRuleBase.assertObject(ReteooRuleBase.java:280)
at org.drools.reteoo.ReteooWorkingMemory$WorkingMemoryReteAssertAction.execute(ReteooWorkingMemory.java:360)
at org.drools.common.AbstractWorkingMemory.executeQueuedActions(AbstractWorkingMemory.java:1471)
... 24 more