Sample project to highlight logging issue during retries

Retry functionality is working as expected, the logs however contain messages logged at ERROR level.

Issue

• Original exception is not visible in logs
• DefaultErrorHanlder logs KafkaBackoffException with ERROR level

Expected behavior

• Original exception is logged with configurable log-level
• DefaultErrorHanlder is using a configurable log-level for KafkaBackoffException

Details

Running ./mvnw clean test will run some tests where different messages are received. When receiving bar, a RuntimeException is thrown. The retry-topics are configured to have a fixed backoff of 5000ms. The logs contain the following lines:

2022-04-02 12:07:07.864 ERROR 10236 --- [e.retry-0-0-C-1] o.s.kafka.listener.DefaultErrorHandler   : Recovery of record (topic-spring-kafka-logging-issue.retry-0-0@0) failed

org.springframework.kafka.listener.ListenerExecutionFailedException: Listener failed; nested exception is org.springframework.kafka.listener.KafkaBackoffException: Partition 0 from topic topic-spring-kafka-logging-issue.retry-0 is not ready for consumption, backing off for approx. 4495 millis.

Following a suggestions from StackOverflow, the ListenerContainer's log-level can be configured. However, the DefaultErrorHandler is using a hard-coded level:

this.logger.error(ex,()->"Recovery of record...