Create your first durable function in PowerShell

Durable Functions is an extension of Azure Functions that lets you write stateful functions in a serverless environment. The extension manages state, checkpoints, and restarts for you.

In this article, you learn how to use the Visual Studio Code Azure Functions extension to locally create and test a "hello world" durable function. This function will orchestrate and chain together calls to other functions. You then publish the function code to Azure.

Running durable function in Azure

Prerequisites

To complete this tutorial:

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

Create your local project

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

  1. In Visual Studio Code, press F1 (or Ctrl/Cmd+Shift+P) to open the command palette. In the command palette, search for and select Azure Functions: Create New Project....

    Create function

  2. Choose an empty folder location for your project and choose Select.

  3. Following the prompts, provide the following information:

    Prompt Value Description
    Select a language for your function app project PowerShell Create a local PowerShell Functions project.
    Select a version Azure Functions v3 You only see this option when the Core Tools aren't already installed. In this case, Core Tools are installed the first time you run the app.
    Select a template for your project's first function Skip for now
    Select how you would like to open your project Open in current window Reopens VS Code in the folder you selected.

Visual Studio Code installs the Azure Functions Core Tools, if needed. It also creates a function app project in a folder. This project contains the host.json and local.settings.json configuration files.

A package.json file is also created in the root folder.

Configure function app to use PowerShell 7

Open the local.settings.json file and confirm that a setting named FUNCTIONS_WORKER_RUNTIME_VERSION is set to ~7. If it is missing or set to another value, update the contents of the file.

{
  "IsEncrypted": false,
  "Values": {
    "AzureWebJobsStorage": "",
    "FUNCTIONS_WORKER_RUNTIME": "powershell",
    "FUNCTIONS_WORKER_RUNTIME_VERSION" : "~7"
  }
}

Create your functions

The most basic Durable Functions app contains three functions:

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

Orchestrator function

You use a template to create the durable function code in your project.

  1. In the command palette, search for and select Azure Functions: Create Function....

  2. Following the prompts, provide the following information:

    Prompt Value Description
    Select a template for your function Durable Functions orchestrator (preview) Create a Durable Functions orchestration
    Provide a function name HelloOrchestrator Name of your durable function

You've added an orchestrator to coordinate activity functions. Open HelloOrchestrator/run.ps1 to see the orchestrator function. Each call to the Invoke-ActivityFunction cmdlet invokes an activity function named Hello.

Next, you'll add the referenced Hello activity function.

Activity function

  1. In the command palette, search for and select Azure Functions: Create Function....

  2. Following the prompts, provide the following information:

    Prompt Value Description
    Select a template for your function Durable Functions activity (preview) Create an activity function
    Provide a function name Hello Name of your activity function

You've added the Hello activity function that is invoked by the orchestrator. Open Hello/run.ps1 to see that it's taking a name as input and returning a greeting. An activity function is where you'll perform actions such as making a database call or performing a computation.

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

Client function (HTTP starter)

  1. In the command palette, search for and select Azure Functions: Create Function....

  2. Following the prompts, provide the following information:

    Prompt Value Description
    Select a template for your function Durable Functions HTTP starter (preview) Create an HTTP starter function
    Provide a function name HttpStart Name of your activity function
    Authorization level Anonymous For demo purposes, allow the function to be called without authentication

You've added an HTTP triggered function that starts an orchestration. Open HttpStart/run.ps1 to see that it uses the Start-NewOrchestration cmdlet to start a new orchestration. Then it uses the New-OrchestrationCheckStatusResponse cmdlet 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.

Test the function locally

Azure Functions Core Tools lets you run an Azure Functions project on your local development computer. You're prompted to install these tools the first time you start a function app from Visual Studio Code.

  1. To test your function, set a breakpoint in the Hello activity function code (Hello/run.ps1). Press F5 or select Debug: Start Debugging from the command palette to start the function app project. Output from Core Tools is displayed in the Terminal panel.

    Note

    Refer to the Durable Functions Diagnostics for more information on debugging.

  2. Durable Functions requires an Azure Storage account to run. When VS Code prompts you to select a storage account, choose Select storage account.

    Create storage account

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

    Prompt Value Description
    Select subscription name of your subscription Select your Azure subscription
    Select a storage account Create a new storage account
    Enter the name of the new storage account unique name Name of the storage account to create
    Select a resource group unique name Name of the resource group to create
    Select a location region Select a region close to you
  4. In the Terminal panel, copy the URL endpoint of your HTTP-triggered function.

    Azure local output

  5. Using your browser, or a tool like Postman or cURL, 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 initial result from the HTTP function letting you know the durable orchestration has started successfully. It is not yet the end result of the orchestration. The response includes a few useful URLs. For now, let's query the status of the orchestration.

  6. Copy the URL value for statusQueryGetUri and paste it in the browser's address bar and execute the request. Alternatively you can also continue to use Postman to issue the GET request.

    The request will query the orchestration instance for the status. You should get an eventual response, which shows us the instance has completed, and includes the outputs or results of the durable function. It looks like:

    {
        "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"
    }
    
  7. To stop debugging, press Shift + F5 in VS Code.

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

Sign in to Azure

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

  1. If you aren't already signed in, choose the Azure icon in the Activity bar, then in the Azure: Functions area, choose Sign in to Azure.... If you don't already have one, you can Create a free Azure account. Students can create a free Azure account for Students.

    Sign in to Azure within VS Code

    If you're already signed in, go to the next section.

  2. When prompted in the browser, choose your Azure account and sign in using your Azure account credentials.

  3. After you've successfully signed in, you can close the new browser window. The subscriptions that belong to your Azure account are displayed in the Side bar.

Publish the project to Azure

In this section, you create a function app and related resources in your Azure subscription and then deploy your code.

Important

Publishing to an existing function app overwrites the content of that app in Azure.

  1. Choose the Azure icon in the Activity bar, then in the Azure: Functions area, choose the Deploy to function app... button.

    Publish your project to Azure

  2. Provide the following information at the prompts:

    • Select folder: Choose a folder from your workspace or browse to one that contains your function app. You won't see this if you already have a valid function app opened.

    • Select subscription: Choose the subscription to use. You won't see this if you only have one subscription.

    • Select Function App in Azure: Choose + Create new Function App. (Don't choose the Advanced option, which isn't covered in this article.)

    • Enter a globally unique name for the function app: Type a name that is valid in a URL path. The name you type is validated to make sure that it's unique in Azure Functions.

    • Select a runtime: Choose the version of PowerShell you've been running on locally. You can use the pwsh -version command to check your version.

      Note

      The Azure Functions VS Code extension may not support PowerShell 7 yet. If PowerShell 7 is not available as an option, select PowerShell 6.x for now and update the version manually after the function app has been created.

    • Select a location for new resources: For better performance, choose a region near you.

  3. When completed, the following Azure resources are created in your subscription, using names based on your function app name:

    • 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 consumption plan, which defines the underlying host for your serverless function app.
    • 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 Application Insights instance connected to the function app, which tracks usage of your serverless function.

    A notification is displayed after your function app is created and the deployment package is applied.

  4. If you were unable to select PowerShell 7 earlier when creating the function app, press F1 (or Ctrl/Cmd+Shift+P) to open the command palette. In the command palette, search for and select Azure Functions: Upload Local Settings.... Follow the prompts to select the function app you created. If prompted to overwrite existing settings, select No to all.

  5. Select View Output in this notification 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.

    Create complete notification

Test your function in Azure

  1. Copy the URL of the HTTP trigger from the Output panel. The URL that calls your HTTP-triggered function should be in this format: http://<functionappname>.azurewebsites.net/api/orchestrators/HelloOrchestrator

  2. Paste this new URL for the HTTP request into your browser's address bar. You should get the same status response as before when using the published app.

Next steps

You have used Visual Studio Code to create and publish a PowerShell durable function app.