Kafka client examples

This module contains some Kafka client examples.

1. Start a local single-broker Kafka cluster with a plain listener configured on port 9092.
2. Run examples/bin/java-producer-consumer-demo.sh 10000 to asynchronously send 10k records to topic1 and consume them.
3. Run examples/bin/java-producer-consumer-demo.sh 10000 sync to synchronous send 10k records to topic1 and consume them.
4. Run examples/bin/exactly-once-demo.sh 6 3 10000 to create input-topic and output-topic with 6 partitions each, start 3 transactional application instances and process 10k records.