Send events to external systems using Output Bindings

Using bindings, its possible to invoke external resources without tying in to special SDK or libraries. For a complete sample showing output bindings, visit this link.

1. Create a binding

An output binding represents a resource that Dapr will use invoke and send messages to.

For the purpose of this guide, we’ll use a Kafka binding. You can find a list of the different binding specs here.

Create the following YAML file, named binding.yaml, and save this to the /components sub-folder in your application directory.

Note: When running in Kubernetes, apply this file to your cluster using kubectl apply -f binding.yaml

apiVersion: dapr.io/v1alpha1
kind: Component
metadata:
  name: myEvent
spec:
  type: bindings.kafka
  metadata:
  - name: brokers
    value: localhost:9092
  - name: publishTopic
    value: topic1

Here, we create a new binding component with the name of myEvent.
Inside the metadata section, we configure Kafka related properties such as the topic to publish the message to and the broker.

2. Send an event

All that’s left now is to invoke the bindings endpoint on a running Dapr instance.

We can do so using HTTP:

curl -X POST -H  http://localhost:3500/v1.0/bindings/myEvent -d '{ data: { "message": "Hi!" } }'

As seen above, we invoked the /binding endpoint with the name of the binding to invoke, in our case its myEvent.
The payload goes inside the data field.