Quickstart: Create a Python Durable Functions app

บทความ
08/21/2024

Use Durable Functions, a feature of Azure Functions, to write stateful functions in a serverless environment. You install Durable Functions by installing the Azure Functions extension in Visual Studio Code. The extension manages state, checkpoints, and restarts in your application.

In this quickstart, you use the Durable Functions extension in Visual Studio Code to locally create and test a "hello world" Durable Functions app in Azure Functions. The Durable Functions app orchestrates and chains together calls to other functions. Then, you publish the function code to Azure. The tools you use are available via the Visual Studio Code extension.

Screenshot of the running Durable Functions app in Azure.

Prerequisites

To complete this quickstart, you need:

Visual Studio Code installed.
The Visual Studio Code extension Azure Functions installed.
The latest version of Azure Functions Core Tools installed.
An HTTP test tool that keeps your data secure. For more information, see HTTP test tools.
An Azure subscription. To use Durable Functions, you must have an Azure Storage account.
Python version 3.7, 3.8, 3.9, or 3.10 installed.

If you don't have an Azure subscription, create an Azure free account before you begin.

Create your local project

In this section, you use Visual Studio Code to create a local Azure Functions project.

In Visual Studio Code, select F1 (or select Ctrl/Cmd+Shift+P) to open the command palette. At the prompt (>), enter and then select Azure Functions: Create New Project.
Select Browse. In the Select Folder dialog, go to a folder to use for your project, and then choose Select.

At the prompts, provide the following information:

Prompt	Action	Description
Select a language for your function app project	Select Python.	Creates a local Python Functions project.
Select a version	Select Azure Functions v4.	You see this option only when Core Tools isn't already installed. In this case, Core Tools is installed the first time you run the app.
Python version	Select Python 3.7, Python 3.8, Python 3.9, or Python 3.10.	Visual Studio Code creates a virtual environment by using the version you select.
Select a template for your project's first function	Select Skip for now.
Select how you would like to open your project	Select Open in current window.	Opens Visual Studio Code in the folder you selected.

At the prompts, provide the following information:

Prompt	Value	Description
Select a language	Select Python (Programming Model V2).	Creates a local Python Functions project by using the V2 programming model.
Select a version	Select Azure Functions v4.	You see this option only when Core Tools isn't already installed. In this case, Core Tools is installed the first time you run the app.
Python version	Select Python 3.7, Python 3.8, Python 3.9, or Python 3.10.	Visual Studio Code creates a virtual environment by using the version you select.
Select how you would like to open your project	Select Open in current window.	Opens Visual Studio Code in the folder you selected.

Visual Studio Code installs Azure Functions Core Tools if it's required to create a project. It also creates a function app project in a folder. This project contains the host.json and local.settings.json configuration files.

A requirements.txt file is also created in the root folder. It specifies the Python packages required to run your function app.

Install azure-functions-durable from PyPI

When you create the project, the Azure Functions Visual Studio Code extension automatically creates a virtual environment with your selected Python version. You then need to activate the virtual environment in a terminal and install some dependencies required by Azure Functions and Durable Functions.

Open the requirements.txt in the editor and change its content to the following code:
```
azure-functions
azure-functions-durable
```
In the current folder, open the editor's integrated terminal (Ctrl+Shift+`).
In the integrated terminal, activate the virtual environment in the current folder, depending on your operating system.
- Linux
- macOS
- Windows
```
source .venv/bin/activate
```
```
source .venv/bin/activate
```
```
.venv\scripts\activate
```

Then, in the integrated terminal where the virtual environment is activated, use pip to install the packages you defined.

python -m pip install -r requirements.txt

Create your functions

The most basic Durable Functions app has three functions:

Orchestrator function: A workflow that orchestrates other functions.
Activity function: A function that is called by the orchestrator function, performs work, and optionally returns a value.
Client function: A regular function in Azure that starts an orchestrator function. This example uses an HTTP-triggered function.

Orchestrator function

You use a template to create the Durable Functions app code in your project.

In the command palette, enter and then select Azure Functions: Create Function.

At the prompts, provide the following information:

Prompt	Action	Description
Select a template for your function	Select Durable Functions orchestrator.	Creates a Durable Functions app orchestration.
Provide a function name	Select HelloOrchestrator.	A name for your durable function.

You added an orchestrator to coordinate activity functions. Open HelloOrchestrator/__init__.py to see the orchestrator function. Each call to context.call_activity invokes an activity function named Hello.

Next, you add the referenced Hello activity function.

Activity function

In the command palette, enter and then select Azure Functions: Create Function.

At the prompts, provide the following information:

Prompt	Action	Description
Select a template for your function	Select Durable Functions activity.	Creates an activity function.
Provide a function name	Enter Hello.	The name of your activity function.

You added the Hello activity function that is invoked by the orchestrator. Open Hello/__init__.py to see that it takes a name as input and returns a greeting. An activity function is where you perform actions such as making a database call or performing a computation.

Finally, you add an HTTP-triggered function that starts the orchestration.

Client function (HTTP starter)

In the command palette, enter and then select Azure Functions: Create Function.

At the prompts, provide the following information:

Prompt	Action	Description
Select a template for your function	Select Durable Functions HTTP starter.	Creates an HTTP starter function.
Provide a function name	Enter DurableFunctionsHttpStart.	The name of your client function
Authorization level	Select Anonymous.	For demo purposes, this value allows the function to be called without using authentication.

You added an HTTP-triggered function that starts an orchestration. Open DurableFunctionsHttpStart/__init__.py to see that it uses client.start_new to start a new orchestration. Then it uses client.create_check_status_response to return an HTTP response containing URLs that can be used to monitor and manage the new orchestration.

You now have a Durable Functions app that can be run locally and deployed to Azure.

Requirements

Version 2 of the Python programming model requires the following minimum versions:

Azure Functions Runtime v4.16+
Azure Functions Core Tools v4.0.5095+ (if running locally)
azure-functions-durable v1.2.4+

Enable the v2 programming model

The following application setting is required to run the v2 programming model:

Name: AzureWebJobsFeatureFlags
Value: EnableWorkerIndexing

If you're running locally by using Azure Functions Core Tools, add this setting to your local.settings.json file. If you're running in Azure, complete these steps by using a relevant tool:

Replace <FUNCTION_APP_NAME> and <RESOURCE_GROUP_NAME> with the name of your function app and resource group, respectively.

az functionapp config appsettings set --name <FUNCTION_APP_NAME> --resource-group <RESOURCE_GROUP_NAME> --settings AzureWebJobsFeatureFlags=EnableWorkerIndexing

Replace <FUNCTION_APP_NAME> and <RESOURCE_GROUP_NAME> with the name of your function app and resource group, respectively.

Update-AzFunctionAppSetting -Name <FUNCTION_APP_NAME> -ResourceGroupName <RESOURCE_GROUP_NAME> -AppSetting @{"AzureWebJobsFeatureFlags" = "EnableWorkerIndexing"}

Make sure that you have the Azure Functions extension for Visual Studio Code installed.
Select F1 to open the command palette. At the prompt (>), enter and then select Azure Functions: Add New Setting.
Select your subscription and function app when you are prompted.
For the name, enter AzureWebJobsFeatureFlags, and then select Enter.
For the value, enter EnableWorkerIndexing, and then select Enter.

To create a basic Durable Functions app by using these three function types, replace the contents of function_app.py with the following Python code:

import azure.functions as func
import azure.durable_functions as df

myApp = df.DFApp(http_auth_level=func.AuthLevel.ANONYMOUS)

# An HTTP-triggered function with a Durable Functions client binding
@myApp.route(route="orchestrators/{functionName}")
@myApp.durable_client_input(client_name="client")
async def http_start(req: func.HttpRequest, client):
    function_name = req.route_params.get('functionName')
    instance_id = await client.start_new(function_name)
    response = client.create_check_status_response(req, instance_id)
    return response

# Orchestrator
@myApp.orchestration_trigger(context_name="context")
def hello_orchestrator(context):
    result1 = yield context.call_activity("hello", "Seattle")
    result2 = yield context.call_activity("hello", "Tokyo")
    result3 = yield context.call_activity("hello", "London")

    return [result1, result2, result3]

# Activity
@myApp.activity_trigger(input_name="city")
def hello(city: str):
    return f"Hello {city}"

Review the following table for an explanation of each function and its purpose in the sample:

Method	Description
`hello_orchestrator`	The orchestrator function, which describes the workflow. In this case, the orchestration starts, invokes three functions in a sequence, and then returns the ordered results of all three functions in a list.
`hello`	The activity function, which performs the work that is orchestrated. The function returns a simple greeting to the city passed as an argument.
`http_start`	An HTTP-triggered function that starts an instance of the orchestration and returns a `check status` response.

Note

Durable Functions also supports Python v2 blueprints. To use blueprints, register your blueprint functions by using the azure-functions-durable Blueprint class. You can register the resulting blueprint as usual. You can use our sample as an example.

Test the function locally

Azure Functions Core Tools gives you the capability to run an Azure Functions project on your local development computer. If it isn't installed, you're prompted to install these tools the first time you start a function in Visual Studio Code.

To test your function, set a breakpoint in the Hello activity function code (in Hello/__init__.py). Select F5 or select Debug: Start Debugging in the command palette to start the function app project. Output from Core Tools appears in the terminal panel.

Note

For more information about debugging, see Durable Functions diagnostics.

To test your function, set a breakpoint in the hello activity function code. Select F5 or select Debug: Start Debugging in the command palette to start the function app project. Output from Core Tools appears in the terminal panel.

Note

For more information about debugging, see Durable Functions diagnostics.

Durable Functions requires an Azure storage account to run. When Visual Studio Code prompts you to select a storage account, select Select storage account.

At the prompts, provide the following information to create a new storage account in Azure.

Prompt	Action	Description
Select subscription	Select the name of your subscription.	Your Azure subscription.
Select a storage account	Select Create a new storage account.
Enter the name of the new storage account	Enter a unique name.	The name of the storage account to create.
Select a resource group	Enter a unique name.	The name of the resource group to create.
Select a location	Select an Azure region.	Select a region that is close to you.

In the terminal panel, copy the URL endpoint of your HTTP-triggered function.

Use your browser or an HTTP test tool to send an HTTP POST request to the URL endpoint.

Replace the last segment with the name of the orchestrator function (HelloOrchestrator). The URL should be similar to http://localhost:7071/api/orchestrators/HelloOrchestrator.

The response is the HTTP function's initial result. It lets you know that the durable orchestration has started successfully. It doesn't yet display the end result of the orchestration. The response includes a few useful URLs. For now, query the status of the orchestration.
Copy the URL value for statusQueryGetUri, paste it in your browser's address bar, and execute the request. You can also continue to use your HTTP test tool to issue the GET request.

The request queries the orchestration instance for the status. You should see that the instance finished and that it includes the outputs or results of the durable function. It looks similar to this example:
```
{
    "name": "HelloOrchestrator",
    "instanceId": "9a528a9e926f4b46b7d3deaa134b7e8a",
    "runtimeStatus": "Completed",
    "input": null,
    "customStatus": null,
    "output": [
        "Hello Tokyo!",
        "Hello Seattle!",
        "Hello London!"
    ],
    "createdTime": "2020-03-18T21:54:49Z",
    "lastUpdatedTime": "2020-03-18T21:54:54Z"
}
```

Use your browser or an HTTP test tool to send an HTTP POST request to the URL endpoint.

Replace the last segment with the name of the orchestrator function (HelloOrchestrator). The URL should be similar to http://localhost:7071/api/orchestrators/HelloOrchestrator.

The response is the HTTP function's initial result. It lets you know that the durable orchestration has started successfully. It doesn't yet display the end result of the orchestration. The response includes a few useful URLs. For now, query the status of the orchestration.
Copy the URL value for statusQueryGetUri, paste it in your browser's address bar, and execute the request. You can also continue to use your HTTP test tool to issue the GET request.

The request queries the orchestration instance for the status. You should see that the instance finished and that it includes the outputs or results of the durable function. It looks similar to this example:
```
{
    "name": "hello_orchestrator",
    "instanceId": "9a528a9e926f4b46b7d3deaa134b7e8a",
    "runtimeStatus": "Completed",
    "input": null,
    "customStatus": null,
    "output": [
        "Hello Tokyo!",
        "Hello Seattle!",
        "Hello London!"
    ],
    "createdTime": "2020-03-18T21:54:49Z",
    "lastUpdatedTime": "2020-03-18T21:54:54Z"
}
```

To stop debugging, in Visual Studio Code, select Shift+F5.

After you verify that the function runs correctly on your local computer, it's time to publish the project to Azure.

Before you can create Azure resources or publish your app, you must sign in to Azure.

If you aren't already signed in, in the Activity bar, select the Azure icon. Then under Resources, select Sign in to Azure.

If you're already signed in and can see your existing subscriptions, go to the next section. If you don't yet have an Azure account, select Create an Azure Account. Students can select Create an Azure for Students Account.
When you are prompted in the browser, select your Azure account and sign in by using your Azure account credentials. If you create a new account, you can sign in after your account is created.
After you successfully sign in, you can close the new browser window. The subscriptions that belong to your Azure account are displayed in the side bar.

Create the function app in Azure

In this section, you create a function app and related resources in your Azure subscription. Many of the resource creation decisions are made for you based on default behaviors. For more control over the created resources, you must instead create your function app with advanced options.

In Visual Studio Code, select F1 to open the command palette. At the prompt (>), enter and then select Azure Functions: Create Function App in Azure.

At the prompts, provide the following information:

Prompt	Action
Select subscription	Select the Azure subscription to use. The prompt doesn't appear when you have only one subscription visible under Resources.
Enter a globally unique name for the function app	Enter a name that is valid in a URL path. The name you enter is validated to make sure that it's unique in Azure Functions.
Select a runtime stack	Select the language version you currently run locally.
Select a location for new resources	Select an Azure region. For better performance, select a region near you.

In the Azure: Activity Log panel, the Azure extension shows the status of individual resources as they're created in Azure.

Screenshot that shows the log of Azure resource creation.

When the function app is created, the following related resources are created in your Azure subscription. The resources are named based on the name you entered for your function app.
- A resource group, which is a logical container for related resources.
- A standard Azure Storage account, which maintains state and other information about your projects.
- A function app, which provides the environment for executing your function code. A function app lets you group functions as a logical unit for easier management, deployment, and sharing of resources within the same hosting plan.
- An Azure App Service plan, which defines the underlying host for your function app.
- An Application Insights instance that's connected to the function app, and which tracks the use of your functions in the app.
A notification is displayed after your function app is created and the deployment package is applied.

Tip

By default, the Azure resources required by your function app are created based on the name you enter for your function app. By default, the resources are created with the function app in the same, new resource group. If you want to customize the names of the associated resources or reuse existing resources, publish the project with advanced create options.

Deploy the project to Azure

Important

Deploying to an existing function app always overwrites the contents of that app in Azure.

In the command palette, enter and then select Azure Functions: Deploy to Function App.
Select the function app you just created. When prompted about overwriting previous deployments, select Deploy to deploy your function code to the new function app resource.
When deployment is completed, select View Output to view the creation and deployment results, including the Azure resources that you created. If you miss the notification, select the bell icon in the lower-right corner to see it again.

Test your function in Azure

Copy the URL of the HTTP trigger from the output panel. The URL that calls your HTTP-triggered function must be in this format:

https://<functionappname>.azurewebsites.net/api/orchestrators/HelloOrchestrator

Copy the URL of the HTTP trigger from the output panel. The URL that calls your HTTP-triggered function must be in this format:

https://<functionappname>.azurewebsites.net/api/orchestrators/hello_orchestrator

Paste the new URL for the HTTP request in your browser's address bar. When you use the published app, you can expect to get the same status response that you got when you tested locally.

The Python Durable Functions app that you created and published by using Visual Studio Code is ready to use.

Clean up resources

If you no longer need the resources that you created to complete the quickstart, to avoid related costs in your Azure subscription, delete the resource group and all related resources.

Learn about common Durable Functions app patterns.

แชร์ผ่าน

Quickstart: Create a Python Durable Functions app

Prerequisites

Create your local project

Install azure-functions-durable from PyPI

Create your functions

Orchestrator function

Activity function

Client function (HTTP starter)

Requirements

Enable the v2 programming model

Test the function locally

Create the function app in Azure

Deploy the project to Azure

Test your function in Azure

Clean up resources

คำติชม

แหล่งทรัพยากรเพิ่มเติม

แชร์ผ่าน

Quickstart: Create a Python Durable Functions app

Prerequisites

Create your local project

Install azure-functions-durable from PyPI

Create your functions

Orchestrator function

Activity function

Client function (HTTP starter)

Requirements

Enable the v2 programming model

Test the function locally

Sign in to Azure

Create the function app in Azure

Deploy the project to Azure

Test your function in Azure

Clean up resources

Related content

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แหล่งทรัพยากรเพิ่มเติม