Speaker: Jun Rao, VP of Apache Kafka and Co-founder of Confluent The controller is the brain of Apache Kafka®. A big part of what the controller does is to maintain the consistency of the replicas and determine which replica can be used to serve the clients, especially during individual broker failure. In this talk, Jun will outline the main data flow in the controller—in particular, when a broker fails, how the controller automatically promotes another replica as the leader to serve the clients, and when a broker is started, how the controller resumes the replication pipeline in the restarted broker. Jun will then describe recent improvements to the controller that allow it to handle certain edge cases correctly and increase its performance, which allows for more partitions in a Kafka cluster. Jun Rao is the co-founder of Confluent, a company that provides a streaming data platform on top of Apache Kafka. Previously, Jun was a senior staff engineer at LinkedIn, where he led the development of Kafka, and a researcher at IBM's Almaden research datacenter, where he conducted research on database and distributed systems. Jun is the PMC chair of Apache Kafka and a committer of Cassandra. He writes at https://cnfl.io/blog-jun-rao.