Tutorial: Use identity-based connections instead of secrets with triggers and bindings

This tutorial shows you how to configure Azure Functions to connect to Azure Service Bus queues by using managed identities, instead of secrets stored in the function app settings. The tutorial is a continuation of the Create a function app without default storage secrets in its definition tutorial. To learn more about identity-based connections, see Configure an identity-based connection..

While the procedures shown work generally for all languages, this tutorial currently supports C# class library functions on Windows specifically.

In this tutorial, you learn how to:

Prerequisite

Complete the previous tutorial: Create a function app with identity-based connections.

Create a Service Bus namespace and queue

1. In the Azure portal, choose Create a resource (+).

2. On the Create a resource page, search for and select Service Bus, and then select Create.

3. On the Basics page, use the following table to configure the Service Bus namespace settings. Use the default values for the remaining options.

   Option	Suggested value	Description
   Subscription	Your subscription	The subscription under which your resources are created.
   Resource group	myResourceGroup	The resource group you created with your function app.
   Namespace name	Globally unique name	The namespace of your instance from which to trigger your function. Because the namespace is publicly accessible, you must use a name that is globally unique across Azure. The name must also be between 6 and 50 characters in length, contain only alphanumeric characters and dashes, and can't start with a number.
   Location	myFunctionRegion	The region where you created your function app.
   Pricing tier	Basic	The basic Service Bus tier.

4. Select Review + create. After validation finishes, select Create.

5. After deployment completes, select Go to resource.

6. In your new Service Bus namespace, select + Queue to add a queue.

7. Enter myinputqueue as the new queue's name and select Create.

Now that you have a queue, you can add a role assignment to the managed identity of your function app.

Configure your Service Bus trigger with a managed identity

To use Service Bus triggers with identity-based connections, you need to add the Azure Service Bus Data Receiver role assignment to the managed identity in your function app. This role is required when using managed identities to trigger off of your Service Bus namespace. You can also add your own account to this role, which makes it possible to connect to the Service Bus namespace during local testing.

1. In your Service Bus namespace that you created, select Access control (IAM). This page is where you can view and configure who has access to the resource.

2. Select + Add and select Add role assignment.

3. Search for Azure Service Bus Data Receiver, select it, and then select Next.

4. On the Members tab, under Assign access to, choose Managed Identity

5. Select Select members to open the Select managed identities panel.

6. Confirm that the Subscription is the one in which you created the resources earlier.

7. In the Managed identity selector, choose Function App from the System-assigned managed identity category. The Function App label might have a number in parentheses next to it, indicating the number of apps in the subscription with system-assigned identities.

8. Your app should appear in a list below the input fields. If you don't see it, you can use the Select box to filter the results with your app's name.

9. Select your application. It should move down into the Selected members section. Select Select.

10. Back on the Add role assignment screen, select Review + assign. Review the configuration, and then select Review + assign.

You've granted your function app access to the Service Bus namespace using managed identities.

Connect to the Service Bus in your function app

1. In the portal, search for the function app you created in the previous tutorial, or browse to it in the Function App page.

2. In your function app, expand Settings, and then select Environment variables.

3. In the App settings tab, select + Add to create a setting. Use the information in the following table to enter the Name and Value for the new setting:

   Name	Value	Description
   ServiceBusConnection__fullyQualifiedNamespace	<SERVICE_BUS_NAMESPACE>.servicebus.windows.net	This setting connects your function app to the Service Bus using an identity-based connection instead of secrets.

4. Select Apply, and then select Apply and Confirm to save your changes and restart the app function.

Now that you've prepared the function app to connect to the Service Bus namespace using a managed identity, you can add a new function that uses a Service Bus trigger to your local project.

Add a Service Bus triggered function

1. Run the func init command, as follows, to create a functions project in a folder named LocalFunctionProj with the specified runtime:

   func init LocalFunctionProj --dotnet
   

2. Navigate to the project folder:

   cd LocalFunctionProj
   

3. In the root project folder, run the following command:

   dotnet add package Microsoft.Azure.WebJobs.Extensions.ServiceBus --version 5.2.0
   

   This command replaces the default version of the Service Bus extension package with a version that supports managed identities.

4. Run the following command to add a Service Bus triggered function to the project:

   func new --name ServiceBusTrigger --template ServiceBusQueueTrigger 
   

   This command adds the code for a new Service Bus trigger and a reference to the extension package. You need to add a Service Bus namespace connection setting for this trigger.

5. Open the new ServiceBusTrigger.cs project file and replace the ServiceBusTrigger class with the following code:

   public static class ServiceBusTrigger
   {
       [FunctionName("ServiceBusTrigger")]
       public static void Run([ServiceBusTrigger("myinputqueue", 
           Connection = "ServiceBusConnection")]string myQueueItem, ILogger log)
       {
           log.LogInformation($"C# ServiceBus queue trigger function processed message: {myQueueItem}");
       }
   }
   

   This code sample updates the queue name to myinputqueue, which is the same name as you queue you created earlier. It also sets the name of the Service Bus connection to ServiceBusConnection. This name is the Service Bus namespace used by the identity-based connection ServiceBusConnection__fullyQualifiedNamespace you configured in the portal.

Publish the updated project

1. Run the following command to locally generate the files needed for the deployment package:

   dotnet publish --configuration Release
   

2. Browse to the \bin\Release\netcoreapp3.1\publish subfolder and create a .zip file from its contents.

3. Publish the .zip file by running the following command, replacing the FUNCTION_APP_NAME, RESOURCE_GROUP_NAME, and PATH_TO_ZIP parameters as appropriate:

   az functionapp deploy -n FUNCTION_APP_NAME -g RESOURCE_GROUP_NAME --src-path PATH_TO_ZIP
   

Now that you've updated the function app with the new trigger, you can verify that it works using the identity.

Validate your changes

1. In the portal, search for Application Insights and select Application Insights under Services.

2. In Application Insights, browse or search for your named instance.

3. In your instance, select Live Metrics under Investigate.

4. Keep the previous tab open, and open the Azure portal in a new tab. In your new tab, navigate to your Service Bus namespace, select Queues from the left menu.

5. Select your queue named myinputqueue.

6. Select Service Bus Explorer from the left menu.

7. Send a test message.

8. Select your open Live Metrics tab and see the Service Bus queue execution.

Congratulations! You have successfully set up your Service Bus queue trigger with a managed identity.

Clean up resources

In the preceding steps, you created Azure resources in a resource group. If you don't expect to need these resources in the future, you can delete them by deleting the resource group.

From the Azure portal menu or Home page, select Resource groups. Then, on the Resource groups page, select myResourceGroup.

On the myResourceGroup page, make sure that the listed resources are the ones you want to delete.

Select Delete resource group, type myResourceGroup in the text box to confirm, and then select Delete.

Next steps

In this tutorial, you created a function app with identity-based connections.

Advance to the next article to learn how to manage identity.