Dapr State input binding for Azure Functions

Important

The Dapr Extension for Azure Functions is currently in preview and only supported in Azure Container Apps environments.

The Dapr state input binding allows you to read Dapr state during a function execution.

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("StateInputBinding")]
public static IActionResult Run(
    [HttpTrigger(AuthorizationLevel.Function, "get", Route = "state/{key}")] HttpRequest req,
    [DaprState("statestore", Key = "{key}")] string state,
    ILogger log)
{
    log.LogInformation("C# HTTP trigger function processed a request.");

    return new OkObjectResult(state);
}

Isolated process

More samples for the Dapr input state binding are available in the GitHub repository.

[Function("StateInputBinding")]
public static string Run(
    [HttpTrigger(AuthorizationLevel.Function, "get", Route = "state/{key}")] HttpRequestData req,
    [DaprStateInput("statestore", Key = "{key}")] string state, 
    FunctionContext functionContext)
{
    var log = functionContext.GetLogger("StateInputBinding");
    log.LogInformation("C# HTTP trigger function processed a request.");

    return state;
}

The following example creates a "RetreveOrder" function using the DaprStateInput binding with the DaprServiceInvocationTrigger:

@FunctionName("RetrieveOrder")
public String run(
        @DaprServiceInvocationTrigger(
            methodName = "RetrieveOrder") 
        String payload,
        @DaprStateInput(
            stateStore = "%StateStoreName%",
            key = "order")
        String product,
        final ExecutionContext context)

Node.js v4

In the following example, the Dapr invoke input binding is added as an extraInput and paired with an HTTP trigger, which is registered by the app object:

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

app.generic('StateInputBinding', {
    trigger: trigger.generic({
        type: 'httpTrigger',
        authLevel: 'anonymous',
        methods: ['GET'],
        route: "state/{key}",
        name: "req"
    }),
    extraInputs: [daprStateInput],
    handler: async (request, context) => {
        context.log("Node HTTP trigger function processed a request.");

        const daprStateInputValue = context.extraInputs.get(daprStateInput);
        // print the fetched state value
        context.log(daprStateInputValue);

        return daprStateInputValue;
    }
});

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 daprState:

{
  "bindings": 
    {
      "type": "daprState",
      "direction": "in",
      "dataType": "string",
      "name": "state",
      "stateStore": "statestore",
      "key": "{key}"
    }
}

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

Here's the JavaScript code:

module.exports = async function (context, req) {
    context.log('Current state of this function: ' + context.bindings.daprState);
};

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 daprState:

{
  "bindings": 
    {
      "type": "daprState",
      "direction": "in",
      "key": "order",
      "stateStore": "%StateStoreName%",
      "name": "order"
    }
}

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, $order
)

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

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

Write-Host "$jsonString"

Python v2

The following example shows a Dapr State input binding, which uses the v2 Python programming model. To use the daprState binding alongside 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 State input binding, which uses the v1 Python programming model.

Here's the function.json file for daprState:

{
  "scriptFile": "__init__.py",
  "bindings": 
    {
      "type": "daprState",
      "direction": "in",
      "dataType": "string",
      "name": "state",
      "stateStore": "statestore",
      "key": "{key}"
    }
}

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

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 DaprState to read Dapr state into your function, which supports these parameters:

Parameter	Description
StateStore	The name of the state store to retrieve state.
Key	The name of the key to retrieve from the specified state store.

Isolated process

In the isolated worker model, use the DaprStateInput to read Dapr state into your function, which supports these parameters:

Parameter	Description
StateStore	The name of the state store to retrieve state.
Key	The name of the key to retrieve from the specified state store.

Annotations

The DaprStateInput annotation allows you to read Dapr state into your function.

Element	Description
stateStore	The name of the Dapr state store.
key	The state store key value.

Configuration

Node.js v4

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

Property	Description
stateStore	The name of the state store.
key	The name of the key to retrieve from the specified state store.

Node.js v3

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

function.json property	Description
stateStore	The name of the state store.
key	The name of the key to retrieve from the specified state store.

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

function.json property	Description
key	The name of the key to retrieve from the specified state store.
stateStore	The name of the state store.

Python v2

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

Property	Description
state_store	The name of the state store.
key	The secret key value. The name of the key to retrieve from the specified state store.

Python v1

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

function.json property	Description
stateStore	The name of the state store.
key	The name of the key to retrieve from the specified state store.

See the Example section for complete examples.

Usage

To use the Dapr state input binding, start by setting up a Dapr state store component. You can learn more about which component to use and how to set it up in the official Dapr documentation.

• Dapr state store component specs
• How to: Save state

Python v2

To use the daprState 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 state store.

Next steps

Learn more about Dapr state management.