Can I use processor api in Kafka Streams and read data from a topic in one kafka cluster and pipe data into a kafka topic in ANOTHER kafka cluster?
Is that do-able thing using processor api? I know, its not possible with Stream DSL!
This is not possible with Kafka Streams. It only works against a single cluster.
To copy data across clusters you need to either use MirrorMaker or one of the available replicator tools, for example a Kafka source connector.
KafkaProducer
you will need to go sync writes to guarantee at-least-once processing. Thus, performance is expected to drop. It's not a recommended pattern. – Matthias J. Sax