Ao Li created KAFKA-17371:
-----------------------------
Summary: Flaky test in
DefaultTaskExecutorTest.shouldUnassignTaskWhenRequired
Key: KAFKA-17371
URL: https://issues.apache.org/jira/browse/KAFKA-17371
Project: Kafka
Issue Type: Bug
Reporter: Ao Li
Please see this fork https://github.com/aoli-al/kafka/tree/KAFKA-251 for a
deterministic reproduction.
The test failed with
{code}
expected: not <null>
org.opentest4j.AssertionFailedError: expected: not <null>
at
org.junit.jupiter.api.AssertionFailureBuilder.build(AssertionFailureBuilder.java:152)
at
org.junit.jupiter.api.AssertionFailureBuilder.buildAndThrow(AssertionFailureBuilder.java:132)
at org.junit.jupiter.api.AssertNotNull.failNull(AssertNotNull.java:49)
at
org.junit.jupiter.api.AssertNotNull.assertNotNull(AssertNotNull.java:35)
at
org.junit.jupiter.api.AssertNotNull.assertNotNull(AssertNotNull.java:30)
at org.junit.jupiter.api.Assertions.assertNotNull(Assertions.java:304)
at
org.apache.kafka.streams.processor.internals.tasks.DefaultTaskExecutorTest.shouldUnassignTaskWhenRequired(DefaultTaskExecutorTest.java:233)
at java.base/java.lang.reflect.Method.invoke(Method.java:580)
at java.base/java.util.ArrayList.forEach(ArrayList.java:1596)
at java.base/java.util.ArrayList.forEach(ArrayList.java:1596)
{code}
The root cause of the failure is that `currentTask =
taskManager.assignNextTask(DefaultTaskExecutor.this);` is not an atomic
operation. This means that calling `taskManager.assignNextTask` will unblock
the `verify(taskManager,
timeout(VERIFICATION_TIMEOUT)).assignNextTask(taskExecutor);` statement in the
test method.
If `assertNotNull(taskExecutor.currentTask());` is executed before the
assignment `currentTaks = [...]` the test will fail.
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