Data Bridge

Data-bridge is a microservice specifically tailored to adhere to the UNS data model. It consumes topics from a message broker, translates them to the proper format and publishes them to the other message broker.

How it works

Data-bridge connects to the source broker, that can be either Kafka or MQTT, and subscribes to the topics specified in the configuration. It then processes the messages, and publishes them to the destination broker, that can be either Kafka or MQTT.

In the case where the destination broker is Kafka, messages from multiple topics can be merged into a single topic, making use of the message key to identify the source topic. For example, subscribing to a topic using a wildcard, such as umh.v1.acme.anytown..*, and a merge point of 4, will result in messages from the topics,, umh.v1.acme.anytown and umh.v1.acme.anytown.frob being merged into a single topic, umh.v1.acme.anytown, with the message key being the missing part of the topic name, in this case, foo.baz, etc.

Here is a diagram showing the flow of messages:

graph LR source((MQTT or Kafka broker)) subgraph Messages direction TB msg1(topic: umh/v1/acme/anytown/foo/bar
value: 1) msg2(topic: umh/v1/acme/anytown/foo/baz
value: 2) msg3(topic: umh/v1/acme/anytown
value: 3) msg4(topic: umh/v1/acme/anytown/frob
value: 4) end source --> msg1 source --> msg2 source --> msg3 source --> msg4 msg1 --> bridge msg2 --> bridge msg3 --> bridge msg4 --> bridge bridge{{data-bridge
subscribes to: umh/v1/acme/anytown/#
topic merge point: 4}} subgraph Grouped messages direction TB gmsg1(topic: umh.v1.acme.anytown
value: 1) gmsg2(topic: umh.v1.acme.anytown
key: foo.baz
value: 2) gmsg3(topic: umh.v1.acme.anytown
value: 3) gmsg4(topic: umh.v1.acme.anytown
key: frob
value: 4) end bridge --> gmsg1 bridge --> gmsg2 bridge --> gmsg3 bridge --> gmsg4 dest((Kafka broker)) gmsg1 --> dest gmsg2 --> dest gmsg3 --> dest gmsg4 --> dest

The value of the message is not changed, only the topic and key are modified.

Another important feature is that it is possible to configure multiple data bridges, each with its own source and destination brokers, and each with its own set of topics to subscribe to and merge point.

The brokers can be local or remote, and, in case of MQTT, they can be secured using TLS.

What’s next

  • Read the Data Bridge reference documentation to learn more about the technical details of the data-bridge microservice.