What is SeekToCurrentErrorHandler (now DefaultErrorHandler) in Spring Kafka?

DefaultErrorHandler replaces SeekToCurrentErrorHandler (and RecoveringBatchErrorHandler). It implements CommonErrorHandler, so it works for record and batch listeners, and handles exceptions thrown by @KafkaListener methods. By default it seeks the consumer so the failed record and the unprocessed records of that poll are redelivered; offsets of the records already processed are committed first. Retries follow a BackOff, and the default is FixedBackOff(0L, 9): no delay and 9 retries, so 10 attempts in total. In FixedBackOff(interval, maxAttempts) the second argument counts retries, so FixedBackOff(1000L, 3) means 3 retries, 4 deliveries. When retries are exhausted the recoverer is invoked; the default recoverer only logs the record at ERROR, and a DeadLetterPublishingRecoverer can publish it to a dead letter topic instead (named <originalTopic>-dlt by default). Supports FixedBackOff and ExponentialBackOff (use ExponentialBackOffWithMaxRetries to cap retries). Some exceptions, such as DeserializationException and MessageConversionException, are not retried and go straight to the recoverer; add more with addNotRetryableExceptions. Configure: factory.setCommonErrorHandler(new DefaultErrorHandler(recoverer, new FixedBackOff(1000L, 3))).

Expected key concepts: DefaultErrorHandler, SeekToCurrentErrorHandler, CommonErrorHandler, BackOff, FixedBackOff, ExponentialBackOff, DeadLetterPublishingRecoverer, recoverer, seek, retries, addNotRetryableExceptions