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Brokers

Brokers can be used in combination with triggers to deliver events from an event source to an event sink. Events are sent from an event source to a broker as an HTTP POST request. After events have entered the broker, they can be filtered by CloudEvent attributes using triggers, and sent as an HTTP POST request to an event sink.

Broker event delivery overview

Broker types

Cluster administrators can set the default broker implementation for a cluster. When you create a broker, the default broker implementation is used, unless you provide set configurations in the Broker object.

Default broker implementation for development purposes

Knative provides a default, channel-based broker implementation. This channel-based broker can be used for development and testing purposes, but does not provide adequate event delivery guarantees for production environments. The default broker is backed by the InMemoryChannel channel implementation by default.

If you want to use Kafka to reduce network hops, use the Kafka broker implementation. Do not configure the channel-based broker to be backed by the KafkaChannel channel implementation.

Production-ready Kafka broker implementation

For production-ready Knative Eventing deployments, Red Hat recommends using the Knative Kafka broker implementation. The Kafka broker is an Apache Kafka native implementation of the Knative broker, which sends CloudEvents directly to the Kafka instance.

The Federal Information Processing Standards (FIPS) mode is disabled for Kafka broker.

The Kafka broker has a native integration with Kafka for storing and routing events. This allows better integration with Kafka for the broker and trigger model over other broker types, and reduces network hops. Other benefits of the Kafka broker implementation include:

  • At-least-once delivery guarantees

  • Ordered delivery of events, based on the CloudEvents partitioning extension

  • Control plane high availability

  • A horizontally scalable data plane

The Knative Kafka broker stores incoming CloudEvents as Kafka records, using the binary content mode. This means that all CloudEvent attributes and extensions are mapped as headers on the Kafka record, while the data spec of the CloudEvent corresponds to the value of the Kafka record.

Next steps