[FLINK-15964] Getting previous stage in notFollowedBy may throw exception

• Type: Bug
• Status: Open
• Priority: Not a Priority
• Resolution: Unresolved
• Affects Version/s: 1.9.0
• Component/s: Library / CEP
• Labels: auto-deprioritized-major auto-deprioritized-minor auto-unassigned pull-request-available
• Assignee: Unassigned
• Reporter: shuai.xu
• Created: 10/Feb/20 07:31
• Updated: 17/Apr/22 22:38

Description

In a notFollowedBy() condition, it may throw exception if trying to get value from previous stage for comparison.

For example:

Pattern<Event, ?> pattern = Pattern.<Event>begin("start", AfterMatchSkipStrategy.skipPastLastEvent())
.notFollowedBy("not").where(new IterativeCondition<Event>() {
private static final long serialVersionUID = -4702359359303151881L;

@Override
public boolean filter(Event value, Context<Event> ctx) throws Exception

{ return value.getName().equals(ctx.getEventsForPattern("start").iterator().next().getName()); }

})
.followedBy("middle").where(new IterativeCondition<Event>() {
@Override
public boolean filter(Event value, Context<Event> ctx) throws Exception

{ return value.getName().equals("b"); }

});

with inputs:
Event a = new Event(40, "a", 1.0);
Event b1 = new Event(41, "a", 2.0);
Event b2 = new Event(43, "b", 3.0);

It will throw 

org.apache.flink.util.FlinkRuntimeException: Failure happened in filter function.org.apache.flink.util.FlinkRuntimeException: Failure happened in filter function.
at org.apache.flink.cep.nfa.NFA.findFinalStateAfterProceed(NFA.java:698) at org.apache.flink.cep.nfa.NFA.computeNextStates(NFA.java:628) at org.apache.flink.cep.nfa.NFA.doProcess(NFA.java:292) at org.apache.flink.cep.nfa.NFA.process(NFA.java:228) at org.apache.flink.cep.utils.NFATestHarness.consumeRecord(NFATestHarness.java:107) at org.apache.flink.cep.utils.NFATestHarness.feedRecord(NFATestHarness.java:84) at org.apache.flink.cep.utils.NFATestHarness.feedRecords(NFATestHarness.java:77) at org.apache.flink.cep.nfa.NFAITCase.testEndWithNotFollow(NFAITCase.java:2914) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:498) at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50) at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12) at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47) at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17) at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26) at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:27) at org.junit.rules.TestWatcher$1.evaluate(TestWatcher.java:55) at org.junit.rules.RunRules.evaluate(RunRules.java:20) at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325) at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78) at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57) at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290) at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71) at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288) at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58) at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268) at org.junit.runners.ParentRunner.run(ParentRunner.java:363) at org.junit.runner.JUnitCore.run(JUnitCore.java:137) at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68) at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47) at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242) at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)Caused by: java.util.NoSuchElementException at java.util.Collections$EmptyIterator.next(Collections.java:4189) at org.apache.flink.cep.nfa.NFAITCase$154.filter(NFAITCase.java:2884) at org.apache.flink.cep.nfa.NFAITCase$154.filter(NFAITCase.java:2879) at org.apache.flink.cep.nfa.NFA.checkFilterCondition(NFA.java:752) at org.apache.flink.cep.nfa.NFA.findFinalStateAfterProceed(NFA.java:688) ... 33 more

Issue Links

• links to: GitHub Pull Request #11068