Output bindings enable you to invoke external resources without taking dependencies on special SDK or libraries. For a complete sample showing output bindings, visit this link.
Watch this video on how to use bi-directional output bindings.
An output binding represents a resource that Dapr uses to invoke and send messages to.
For the purpose of this guide, you’ll use a Kafka binding. You can find a list of the different binding specs here.
Create a new binding component with the name of myevent
.
Inside the metadata
section, configure Kafka related properties such as the topic to publish the message to and the broker.
Create the following YAML file, named binding.yaml
, and save this to a components
sub-folder in your application directory.
(Use the --components-path
flag with dapr run
to point to your custom components dir)
apiVersion: dapr.io/v1alpha1
kind: Component
metadata:
name: myevent
namespace: default
spec:
type: bindings.kafka
version: v1
metadata:
- name: brokers
value: localhost:9092
- name: publishTopic
value: topic1
To deploy this into a Kubernetes cluster, fill in the metadata
connection details of your desired binding component in the yaml below (in this case kafka), save as binding.yaml
, and run kubectl apply -f binding.yaml
.
apiVersion: dapr.io/v1alpha1
kind: Component
metadata:
name: myevent
namespace: default
spec:
type: bindings.kafka
version: v1
metadata:
- name: brokers
value: localhost:9092
- name: publishTopic
value: topic1
All that’s left now is to invoke the output bindings endpoint on a running Dapr instance.
You can do so using HTTP:
curl -X POST -H 'Content-Type: application/json' http://localhost:3500/v1.0/bindings/myevent -d '{ "data": { "message": "Hi!" }, "operation": "create" }'
As seen above, you invoked the /binding
endpoint with the name of the binding to invoke, in our case its myevent
.
The payload goes inside the mandatory data
field, and can be any JSON serializable value.
You’ll also notice that there’s an operation
field that tells the binding what you need it to do.
You can check here which operations are supported for every output binding.