Dapr Service Invocation trigger for Azure Functions

Azure Functions can be triggered on a Dapr service invocation using the following Dapr events.

For information on setup and configuration details of the Dapr extension, see the Dapr extension overview.

Example

A C# function can be created using one of the following C# modes:

Execution model	Description
Isolated worker model	Your function code runs in a separate .NET worker process. Use with supported versions of .NET and .NET Framework. To learn more, see Develop .NET isolated worker process functions.
In-process model	Your function code runs in the same process as the Functions host process. Supports only Long Term Support (LTS) versions of .NET. To learn more, see Develop .NET class library functions.

In-process

[FunctionName("CreateNewOrder")]
public static void Run(
    [DaprServiceInvocationTrigger] JObject payload,
    [DaprState("%StateStoreName%", Key = "order")] out JToken order,
    ILogger log)
{
    log.LogInformation("C# function processed a CreateNewOrder request from the Dapr Runtime.");

    // payload must be of the format { "data": { "value": "some value" } }
    order = payload["data"];
}

Isolated process

[Function("CreateNewOrder")]
[DaprStateOutput("%StateStoreName%", Key = "order")]
public static JsonElement Run(
    [DaprServiceInvocationTrigger] JsonElement payload, 
    FunctionContext functionContext)
{
    var log = functionContext.GetLogger("CreateNewOrder");
    log.LogInformation("C# function processed a CreateNewOrder request from the Dapr Runtime.");

    // payload must be of the format { "data": { "value": "some value" } }
    payload.TryGetProperty("data", out JsonElement data);

    return data;
}

Here's the Java code for the Dapr Service Invocation trigger:

@FunctionName("CreateNewOrder")
public String run(
        @DaprServiceInvocationTrigger(
            methodName = "CreateNewOrder") 
)

Node.js v4

Use the app object to register the daprInvokeOutput:

const { app, trigger } = require('@azure/functions');

app.generic('InvokeOutputBinding', {
    trigger: trigger.generic({
        type: 'httpTrigger',
        authLevel: 'anonymous',
        methods: ['POST'],
        route: "invoke/{appId}/{methodName}",
        name: "req"
    }),
    return: daprInvokeOutput,
    handler: async (request, context) => {
        context.log("Node HTTP trigger function processed a request.");

        const payload = await request.text();
        context.log(JSON.stringify(payload));

        return { body: payload };
    }
});

Node.js v3

The following examples show Dapr triggers in a function.json file and JavaScript code that uses those bindings.

Here's the function.json file for daprServiceInvocationTrigger:

{
  "bindings": [
    {
      "type": "daprServiceInvocationTrigger",
      "name": "payload"
    }
  ]
}

For more information about function.json file properties, see the Configuration section.

Here's the JavaScript code:

module.exports = async function (context) {
    context.log("Node function processed a RetrieveOrder request from the Dapr Runtime.");

    // print the fetched state value
    context.log(context.bindings.data);
};

The following examples show Dapr triggers in a function.json file and PowerShell code that uses those bindings.

Here's the function.json file for daprServiceInvocationTrigger:

{
  "bindings": [
    {
      "type": "daprServiceInvocationTrigger",
      "name": "payload",
      "direction": "in"
    }
  ]
}

For more information about function.json file properties, see the Configuration section.

In code:

using namespace System
using namespace Microsoft.Azure.WebJobs
using namespace Microsoft.Extensions.Logging
using namespace Microsoft.Azure.WebJobs.Extensions.Dapr
using namespace Newtonsoft.Json.Linq

param (
    $payload
)

# C# function processed a CreateNewOrder request from the Dapr Runtime.
Write-Host "PowerShell function processed a CreateNewOrder request from the Dapr Runtime."

# Payload must be of the format { "data": { "value": "some value" } }

# Convert the object to a JSON-formatted string with ConvertTo-Json
$jsonString = $payload| ConvertTo-Json

# Associate values to output bindings by calling 'Push-OutputBinding'.
Push-OutputBinding -Name order -Value $payload["data"]

Python v2

The following example shows a Dapr Service Invocation trigger, which uses the v2 Python programming model. To use the daprServiceInvocationTrigger in your Python function app code:

import logging
import json
import azure.functions as func

app = func.FunctionApp()

@app.function_name(name="RetrieveOrder")
@app.dapr_service_invocation_trigger(arg_name="payload", method_name="RetrieveOrder")
@app.dapr_state_input(arg_name="data", state_store="statestore", key="order")
def main(payload, data: str) :
    # Function should be invoked with this command: dapr invoke --app-id functionapp --method RetrieveOrder  --data '{}'
    logging.info('Python function processed a RetrieveOrder request from the Dapr Runtime.')
    logging.info(data)

Python v1

The following example shows a Dapr Service Invocation trigger, which uses the v1 Python programming model.

Here's the function.json file for daprServiceInvocationTrigger:

{
  "scriptFile": "__init__.py",
  "bindings": [
    {
      "type": "daprServiceInvocationTrigger",
      "name": "payload",
      "direction": "in"
    }
  ]
}

For more information about function.json file properties, see the Configuration section.

Here's the Python code:

import logging
import json
import azure.functions as func

def main(payload, data: str) -> None:
    logging.info('Python function processed a RetrieveOrder request from the Dapr Runtime.')
    logging.info(data)

Attributes

In-process

In the in-process model, use the DaprServiceInvocationTrigger to trigger a Dapr service invocation binding, which supports the following properties.

Parameter	Description
MethodName	Optional. The name of the method the Dapr caller should use. If not specified, the name of the function is used as the method name.

Isolated process

In the isolated worker model, use the DaprServiceInvocationTrigger to define a Dapr service invocation trigger, which supports these parameters:

Parameter	Description
MethodName	Optional. The name of the method the Dapr caller should use. If not specified, the name of the function is used as the method name.

Annotations

The DaprServiceInvocationTrigger annotation allows you to create a function that gets invoked by Dapr runtime.

Element	Description
methodName	The method name.

Configuration

Node.js v4

The following table explains the binding configuration properties that you set in the code.

Property	Description
type	Must be set to daprServiceInvocationTrigger.
name	The name of the variable that represents the Dapr data in function code.

Node.js v3

The following table explains the binding configuration properties that you set in the function.json file.

function.json property	Description
type	Must be set to daprServiceInvocationTrigger.
name	The name of the variable that represents the Dapr data in function code.

The following table explains the binding configuration properties that you set in the function.json file.

function.json property	Description
type	Must be set to daprServiceInvocationTrigger.
name	The name of the variable that represents the Dapr data in function code.

Python v2

The following table explains the binding configuration properties for @dapp.dapr_service_invocation_trigger that you set in your Python code.

Property	Description
method_name	The name of the variable that represents the Dapr data.

Python v1

The following table explains the binding configuration properties that you set in the function.json file.

function.json property	Description
type	Must be set to daprServiceInvocationTrigger.
name	The name of the variable that represents the Dapr data in function code.

See the Example section for complete examples.

Usage

To use a Dapr Service Invocation trigger, learn more about which components to use with the Service Invocation trigger and how to set them up in the official Dapr documentation.

• Dapr component specs
• Dapr service invocation

Python v2

To use the daprServiceInvocationTrigger in Python v2, set up your project with the correct dependencies.

1. Create and activate a virtual environment.

2. In your requirements.text file, add the following line:

   azure-functions==1.18.0b3
   

3. In the terminal, install the Python library.

   pip install -r .\requirements.txt
   

4. Modify your local.setting.json file with the following configuration:

   "PYTHON_ISOLATE_WORKER_DEPENDENCIES":1
   

Python v1

The Python v1 model requires no additional changes, aside from setting up the service invocation component.

Next steps

Learn more about Dapr service invocation.