KafkaMessageListenerContainer.getAssignedPartitions is not safe

[tbarabanov]

In what version(s) of Spring for Apache Kafka are you seeing this issue?

3.2.1

Describe the bug

KafkaMessageListenerContainer.getAssignedPartitions() is not safe due to the fact that different threads can iterate/modify any of the fields partitionsListenerConsumer.definedPartitions, partitionsListenerConsumer.assignedPartitions simultaneously, but collection types of these fields are not designed for such scenarios. Thus at least ConcurrentModificationException can be thrown.

Expected behavior

KafkaMessageListenerContainer.getAssignedPartitions() method is public and thus expected to be safe.

[artembilan]

More info in StackOverflow question: https://stackoverflow.com/questions/79383650/is-kafkamessagelistenercontainer-getassignedpartitions-thread-safe.

@tbarabanov ,

feel free to contribute the fix: https://github.com/spring-projects/spring-kafka/blob/main/CONTRIBUTING.adoc!