How do you configure the consumer to start from the beginning for a new application deployment?

For a new consumer group set spring.kafka.consumer.auto-offset-reset=earliest. auto.offset.reset (default latest) says what to do when there is no initial offset in Kafka or the current offset no longer exists on the server; earliest resets to the earliest offset available, which is the start of the log and not necessarily offset 0 if old segments were deleted. For later deployments with the same group-id, committed offsets that are still valid are used and auto-offset-reset has no effect, so earliest on a running group with committed offsets does nothing. To re-read all messages, use a new group id, delete the group (kafka-consumer-groups.sh --delete --group my-group; this works only if the group has no active members), or reset its offsets with kafka-consumer-groups.sh --reset-offsets --to-earliest --execute after making sure the consumer instances are inactive. Within the application you can also seek, for example with ConsumerSeekAware.

Expected key concepts: auto-offset-reset, earliest, latest, new consumer group, committed offsets, group-id, reset-offsets, to-earliest, no active members