Hello Kafka users! Here is a blog post on how we migrated our 0.7 traffic over to 0.8 at Knewton. I hope this might be useful for anyone considering doing a cutover.
http://tech.knewton.com/blog/2015/09/how-knewton-cutover-the-core-of-its-infrastructure-from-kafka-0-7-to-kafka-0-8/
