Using bindings, you can trigger your app with events coming in from external systems, or invoke external systems. This building block provides several benefits for you and your code:
- Remove the complexities of connecting to, and polling from, messaging systems such as queues and message buses
- Focus on business logic and not implementation details of how to interact with a system
- Keep your code free from SDKs or libraries
- Handle retries and failure recovery
- Switch between bindings at run time
- Build portable applications where environment-specific bindings are set-up and no code changes are required
For a specific example, bindings would allow your microservice to respond to incoming Twilio/SMS messages without adding or configuring a third-party Twilio SDK, worrying about polling from Twilio (or using websockets, etc.).
Bindings are developed independently of Dapr runtime. You can view and contribute to the bindings here.
Every binding has its own unique set of properties. Click the name link to see the component YAML for each binding.
| Name | Input Binding |
Output Binding |
Status |
|---|---|---|---|
| Cron (Scheduler) | ✅ | ✅ | Experimental |
| HTTP | ✅ | Experimental | |
| Kafka | ✅ | ✅ | Experimental |
| Kubernetes Events | ✅ | Experimental | |
| MQTT | ✅ | ✅ | Experimental |
| RabbitMQ | ✅ | ✅ | Experimental |
| Redis | ✅ | Experimental | |
| Twilio | ✅ | Experimental | |
| ✅ | Experimental | ||
| SendGrid | ✅ | Experimental |
| Name | Input Binding |
Output Binding |
Status |
|---|---|---|---|
| AWS DynamoDB | ✅ | Experimental | |
| AWS S3 | ✅ | Experimental | |
| AWS SNS | ✅ | Experimental | |
| AWS SQS | ✅ | ✅ | Experimental |
| AWS Kinesis | ✅ | ✅ | Experimental |
| Name | Input Binding |
Output Binding |
Status |
|---|---|---|---|
| GCP Cloud Pub/Sub | ✅ | ✅ | Experimental |
| GCP Storage Bucket | ✅ | Experimental |
| 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 |
| Azure Event Grid | ✅ | ✅ | Experimental |
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:
- Define the component YAML that describes the type of binding and its metadata (connection info, etc.)
- Listen on an HTTP endpoint for the incoming event, or use the gRPC proto library to get incoming events
On startup Dapr sends a
OPTIONSrequest for all defined input bindings to the application and expects a different status code asNOT 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 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:
- Define the component YAML that describes the type of binding and its metadata (connection info, etc.)
- 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.