Kafka Driver

dc3-driver-kafka treats Apache Kafka as a streaming data source. Inbound messages are consumed asynchronously and cached by message key; a point read returns the latest cached value, and a point write produces a message to the configured topic.

Protocol background

Kafka is a distributed publish/subscribe stream. Values arrive asynchronously, so this driver caches the latest message per key (or per topic when the message has no key) and serves reads from that cache while writing produces messages.

• Driver name / code: Kafka Driver / KafkaDriver
• Type: DRIVER_SERVER (passively consumes messages and produces writes)
• Underlying library: Spring Kafka (KafkaTemplate + @KafkaListener)

Attribute configuration

Driver attributes (device-level driver-attribute)

Attribute	code	Type	Default	Description
Topic	topic	STRING	dc3-driver-kafka	Default topic for produce/consume

Point attributes (point-attribute)

Attribute	code	Type	Default	Description
Topic	topic	STRING	(empty)	Override topic for this point
Key	key	STRING	(empty)	Message key used for produce and cache lookup

Command attributes (command-attribute)

Attribute	code	Type	Default	Description
Topic	topic	STRING	(empty)	Override topic for this command

Collection and health

• Collection cycle: default cron 0/30 * * * * ? (one polling round over all points every 30 seconds).
• Health/online: device health defaults to cron 0/15 * * * * ?, lease timeout 45 seconds.

Capability matrix

Capability	Supported	Notes
Read	✓ (latest cached message)
Write	✓
Subscribe	✓

Implementation status: usable ::

Broker connection is configured through Spring Boot spring.kafka.* (KAFKA_BOOTSTRAP_SERVERS); the consumer group id defaults to dc3-driver-kafka-group.

Minimal onboarding example

1. Create a Device using Kafka Driver.
2. Add a Point (READ_ONLY) with key=sensor-1 to read the latest message for that key.
3. Start the driver; messages are consumed from the topic and cached for reads.

Further reading

• Driver overview — entry point to all protocol drivers and selection
• Driver capability matrix — quick reference of read/write/subscribe capabilities
• Device onboarding — a complete onboarding walkthrough