Create your first durable function in PowerShell

Article
07/29/2022

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:

Install Visual Studio Code.
Install the Azure Functions VS Code extension
Make sure you have the latest version of the Azure Functions Core Tools.
Durable Functions require an Azure storage account. You need an Azure subscription.

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

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 v4	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.

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

Following the prompts, provide the following information:

Prompt	Value	Description
Select a template for your function	Durable Functions orchestrator	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

In the command palette, search for and select Azure Functions: Create Function....
Following the prompts, provide the following information:

Prompt Value Description

Select a template for your function Durable Functions activity Create an activity function

Provide a function name Hello Name of your activity function

Prompt	Value	Description
Select a template for your function	Durable Functions activity	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)

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

Following the prompts, provide the following information:

Prompt	Value	Description
Select a template for your function	Durable Functions HTTP starter	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.

Note

The next version of the DF PowerShell is now in preview and may be downloaded from the PowerShell Gallery. Learn about it and how to try it out in the guide to the standalone PowerShell SDK. You may follow the guide's installation section for instructions compatible with this quickstart on how to enable it.

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.

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

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

In the Terminal panel, copy the URL endpoint of your HTTP-triggered function.
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.
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"
}
```
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.

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

If you aren't already signed in, choose the Azure icon in the Activity bar. Then in the Resources area, choose 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, choose Create an Azure Account.... Students can choose Create an Azure for Students Account....
When prompted in the browser, choose your Azure account and sign in using your Azure account credentials. If you create a new account, you can sign in after your account is created.
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 sidebar.

Create the function app in Azure

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

In Visual Studio Code, press F1 to open the command palette and search for and run the command Azure Functions: Create Function App in Azure....

Provide the following information at the prompts:

Prompt	Selection
Select subscription	Choose the subscription to use. You won't see this prompt when you have only one subscription visible under Resources.
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 stack	Choose the language version on which you've been running locally.
Select a location for new resources	For better performance, choose a region near you.

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

Log of Azure resource creation

When the creation is complete, the following Azure resources are created in your subscription. The resources are named 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 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 App Service plan, which defines the underlying host for your function app.
- An Application Insights instance connected to the function app, which tracks usage 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 function app name you provide. By default, they're also created in the same new resource group with the function app. If you want to either customize the names of these resources or reuse existing resources, you need to publish the project with advanced create options instead.

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, search for and run the command 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.
After deployment completes, 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 should be in this format: https://<functionappname>.azurewebsites.net/api/orchestrators/HelloOrchestrator
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.

Learn about common durable function patterns

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Create your first durable function in PowerShell

Prerequisites

Create your local project

Configure function app to use PowerShell 7