The "Channel" implementation is a Kafka Producer which is responsible for receiving CloudEvents, converting them to Kafka Messages, and writing them to the appropriate Kafka Topic.
A unique Channel Deployment / Service is created for every Kafka Secret (in
the knative-eventing namespace and labelled with
knativekafka.kyma-project.io/kafka-secret: "true"). The single Deployment
is horizontally scalable as necessary (via controller environment variables.) This
allows for an efficient use of cluster resources while still supporting high
volume and multi-tenant use cases.
An additional Service for each KafkaChannel is created in the user namespace
where the KafkaChannel exists. This is the actual endpoint of the KafkaChannel
This service forwards requests to the service mentioned above in the
knative-eventing namespace. This is all necessary so that the Channel
implementation can use the hostname of the request to map incoming CloudEvents
to the appropriate Kafka Topic.
The implementation makes use of the Conluent Go Client library, along with the underlying C/C++ librdkafka library. The Kafka brokers and credentials are obtained from mounted Secret data from the aforementiond Kafka Secret.