output-bindings.md

Azure Functions Dapr output bindings

Output bindings allow you to push data to a destination at the end of an execution. The parameters for the output binding can either be set statically in the function.json or attribute definition, use the %env_variable_name% syntax to reference a value from environment variables, or pull from surfaced trigger metadata (e.g. the route parameter of an HTTP triggered function). More details on bindings can be found in the Azure Functions documentation. You can always leverage the Dapr SDK directly within your function instead of using an output binding.

State Output Binding

Save state to a specified key.

If binding to a byte[] or JSON object, the object should be of format:

{
    "value": "The body of the invoke-method operation.",
    "key": "{Optional. If not defined in function.json}",
    "etag": "{Optional. The etag value of the state record.}"
}

Function.json sample

{
    "type": "daprState",
    "direction": "out",
    "name": "state",
    "stateStore": "statestore",
    "key": "{key}"
}

C# Attribute sample

[HttpTrigger(AuthorizationLevel.Function, "get", Route = "state/{key}")] HttpRequest req,
[DaprState("statestore", Key = "{key}")] IAsyncCollector<DaprStateRecord> state,

Properties

Property Name	Description
StateStore	The name of the state store to save state.
Key	The name of the key to save state within the state store.

Service Invocation Output Binding

Invoke another Dapr service.

If binding to a byte[] or JSON object, the object should be of format:

{
    "body": "The body of the invoke-method operation.",
    "appId": "{Optional. If not defined in function.json}",
    "methodName": "{Optional. If not defined in function.json}",
    "httpVerb": "{Optional. If not defined in function.json}"
}

Function.json sample

{
    "type": "daprInvoke",
    "direction": "out",
    "appId": "{appId}",
    "methodName": "{methodName}",
    "httpVerb": "post",
    "name": "output"
}

C# Attribute sample

[HttpTrigger(AuthorizationLevel.Function, "get", Route = "invoke/{appId}/{methodName}")] HttpRequest req,
[DaprInvoke(AppId = "{appId}", MethodName = "{methodName}", HttpVerb = "post")] IAsyncCollector<InvokeMethodParameters> output,

Properties

Property Name	Description
AppId	The Dapr app ID to invoke.
MethodName	The method name of the app to invoke.
HttpVerb	Optional. HTTP verb to use of the app to invoke. Default is POST.

Topic Publish Output Binding

Publish a message to a Dapr topic.

If binding to a byte[] or JSON object, the object should be of format:

{
    "payload": "The subscribers will receive this payload as the body of a Cloud Event envelope.",
    "pubsubname": "{Optional. Name of the pub/sub if not defined in function.json}",
    "topic": "{Optional. Name of the topic if not defined in function.json}"
}

Function.json sample

{
    "type": "daprPublish",
    "direction": "out",
    "name": "pubEvent",
    "pubsubname": "pubsub",
    "topic": "myTopic"
}

C# Attribute sample

[DaprPublish(PubSubName = "pubsub", Topic = "myTopic")] IAsyncCollector<DaprPubSubEvent> pubEvent,

Properties

Property Name	Description
PubSubName	The name of the Dapr pub/sub to send the message.
Topic	The name of the Dapr topic to send the message.

Dapr Binding Output Binding

Send data to a Dapr binding.

If binding to a byte[] or JSON object, the object should be of format:

{
    "data": "Data to send to binding",
    "metadata": "{Optional. The bag of key value pairs for binding-specific metadata}",
    "operation": "{Optional. If not defined in function.json}",
    "bindingName": "{Optional. If not defined in function.json}"
}

Function.json sample

{
    "type": "daprBinding",
    "direction": "out",
    "bindingName": "myKafkaBinding",
    "operation": "create",
    "name": "messages"
}

C# Attribute sample

[DaprBinding(BindingName = "myKafkaBinding", Operation = "create")] IAsyncCollector<DaprBindingMessage> messages,

Properties

Property Name	Description
BindingName	The name of the Dapr binding.
Operation	The configured binding operation.