bindings

README

Bindings

Bindings provide a common way to trigger an application with events from external systems, or invoke an external system with optional data payloads. Bindings are great for event-driven, on-demand compute and help reduce boilerplate code.

List of bindings and their status:

Name	Input Binding	Output Binding	Status
Kafka	V	V	Experimental
RabbitMQ	V	V	Experimental
AWS SQS	V	V	Experimental
AWS SNS		V	Experimental
GCP Cloud Pub/Sub	V	V	Experimental
Azure EventHubs	V	V	Experimental
Azure CosmosDB		V	Experimental
GCP Storage Bucket		V	Experimental
HTTP		V	Experimental
MQTT	V	V	Experimental
Redis		V	Experimental
AWS DynamoDB		V	Experimental
AWS S3		V	Experimental
Azure Blob Storage		V	Experimental
Azure Service Bus Queues	V	V	Experimental
Kubernetes Events	V		Experimental

Implementing a new binding

A compliant binding needs to implement one or more interfaces, depending on the type of binding (Input or Output):

Input binding:

type InputBinding interface {
	Init(metadata Metadata) error
	Read(handler func(*ReadResponse) error) error
}

Output binding:

type OutputBinding interface {
	Init(metadata Metadata) error
	Write(req *WriteRequest) error
}

Documentation

Index

• type AppResponse
• type InputBinding
• type Metadata
• type OutputBinding
• type ReadResponse
• type WriteRequest

Types

type AppResponse

type AppResponse struct {
	Data        interface{}        `json:"data"`
	To          []string           `json:"to"`
	State       []state.SetRequest `json:"state"`
	Concurrency string             `json:"concurrency"`
}

AppResponse is the object describing the response from user code after a bindings event

type InputBinding

type InputBinding interface {
	// Init passes connection and properties metadata to the binding implementation
	Init(metadata Metadata) error
	// Read is a blocking method that triggers the callback function whenever an event arrives
	Read(handler func(*ReadResponse) error) error
}

InputBinding is the interface to define a binding that triggers on incoming events

type Metadata

type Metadata struct {
	Name       string
	Properties map[string]string `json:"properties"`
}

Metadata represents a set of binding specific properties

type OutputBinding

type OutputBinding interface {
	Init(metadata Metadata) error
	Write(req *WriteRequest) error
}

OutputBinding is the interface for an output binding, allowing users to invoke remote systems with optional payloads

type ReadResponse

type ReadResponse struct {
	Data     []byte            `json:"data"`
	Metadata map[string]string `json:"metadata"`
}

ReadResponse is an the return object from an dapr input binding

type WriteRequest

type WriteRequest struct {
	Data     []byte            `json:"data"`
	Metadata map[string]string `json:"metadata"`
}

WriteRequest is the object given to an dapr output binding