docs/concepts/bindings

Bindings

Dapr provides a mechanism that can either (a) trigger your app in response to an event or (b) trigger an external system when your app does something.

For example, bindings allow your microservice to respond to incoming Twilio/SMS messages without adding/configuring a third-party Twilio SDK, worrying about polling from Twilio (or doing websockets, etc...).

Bindings give you some additional advantages:

• Handle retries and failure recovery
• Switch between bindings at runtime time
• Enable portable applications where environment-specific bindings are set-up and no code changes are required

Bindings are developed independently of Dapr runtime. You can view and contribute to the bindings here.

Supported bindings and specs

Every binding has its own unique set of properties. Click the name link to see the component YAML for each binding.

Generic

Name	Input Binding	Output Binding	Status
HTTP		✅	Experimental
Kafka	✅	✅	Experimental
Kubernetes Events	✅		Experimental
MQTT	✅	✅	Experimental
RabbitMQ	✅	✅	Experimental
Redis		✅	Experimental
Twilio		✅	Experimental
SendGrid		✅	Experimental

Amazon Web Service (AWS)

Name	Input Binding	Output Binding	Status
AWS DynamoDB		✅	Experimental
AWS S3		✅	Experimental
AWS SNS		✅	Experimental
AWS SQS	✅	✅	Experimental
AWS Kinesis	✅	✅	Experimental

Google Cloud Platform (GCP)

Name	Input Binding	Output Binding	Status
GCP Cloud Pub/Sub	✅	✅	Experimental
GCP Storage Bucket		✅	Experimental

Microsoft Azure

Name	Input Binding	Output Binding	Status
Azure Blob Storage		✅	Experimental
Azure EventHubs	✅	✅	Experimental
Azure CosmosDB		✅	Experimental
Azure Service Bus Queues	✅	✅	Experimental
Azure SignalR		✅	Experimental
Azure Storage Queues	✅	✅	Experimental

Input bindings

Input bindings are used to trigger your application when an event from an external resource has occurred. An optional payload and metadata might be sent with the request.

In order to receive events from an input binding:

1. Define the component YAML that describes the type of binding and its metadata (connection info, etc.)
2. Listen on an HTTP endpoint for the incoming event, or use the gRPC proto library to get incoming events

On startup Dapr sends a OPTIONS request for all defined input bindings to the application and expects a different status code as NOT FOUND (404) if this application wants to subscribe to the binding.

Read the Create an event-driven app using input bindings section to get started with input bindings.

Output bindings

Output bindings allow users to invoke external resources An optional payload and metadata can be sent with the invocation request.

In order to invoke an output binding:

1. Define the component YAML that describes the type of binding and its metadata (connection info, etc.)
2. Use the HTTP endpoint or gRPC method to invoke the binding with an optional payload

Read the Send events to external systems using Output Bindings section to get started with output bindings.

Related Topics

• Implementing a new binding
• Trigger a service from different resources with input bindings
• Invoke different resources using output bindings