title: How does Flink (Kafka source) manage offsets?
body: <p>I am using Flink's <code>FlinkKafkaConsumer09</code> and I wonder where are the offsets of the kafka consumer stored?</p>
  
  <p>I can't find them in Zookeeper nor in Kafka's offset topic. Also the kafka-consumer-offset tool can't find.</p>
  
  <p>Is this handled by Flink internally?</p>