Use unique topics to avoid "marked for deletion error"

[bkornmeierpax8]

@smcvb I noticed this test failing after merging my changes. In ConsumerPositionsUtilIntegrationTest.java's tearDown method we were deleting the topic, however Kafka won't actually delete the topic right away, it just marks it for deletion. This change provides a unique topic per test, to just avoid the issue entirely.

[bkornmeierpax8]

@smcvb I also noticed that testFetchEventsTaskInterruptionClosesAsExpected is failing some of the time, looking a bit at it I see we wait for the closeHandle to be called in the test:
https://github.com/AxonFramework/extension-kafka/blob/master/kafka/src/test/java/org/axonframework/extensions/kafka/eventhandling/consumer/FetchEventsTaskTest.java#L137-L138

However, in the code, the closing of the consumer happens after the handler is called:

extension-kafka/kafka/src/main/java/org/axonframework/extensions/kafka/eventhandling/consumer/FetchEventsTask.java

Lines 101 to 102 in 7a17590

	closeHandler.accept(this);
	consumer.close();

I am wondering if we may want to add a small delay after the closeHandler is called, we could use Kafka's DEFAULT_CLOSE_TIMEOUT_MS value + 100 millis.

DEFAULT_CLOSE_TIMEOUT_MS is defined here:
https://github.com/apache/kafka/blob/11aa999d2054d3ecb28de2a95ada02131c5d9616/clients/src/main/java/org/apache/kafka/clients/consumer/KafkaConsumer.java#L568

What do you think about that?

[bkornmeierpax8]

Disregard previous comment. I see the we had a similar test in testCloseCallsProvidedCloseHandler and it had a timeout() added, so I just reused that here: a975338

[smcvb]

Thanks for the quick fix here, @bkornmeierpax8.