Create a function in Azure that's triggered by Blob storage

Learn how to create a function triggered when files are uploaded to or updated in a Blob storage container.

Prerequisites

• An Azure subscription. If you don't have one, create a Trial before you begin.

Create an Azure Function app

1. From the Azure portal menu or the Home page, select Create a resource.

2. In the New page, select Compute > Function App.

3. On the Basics page, use the function app settings as specified in the following table:

   Setting	Suggested value	Description
   Subscription	Your subscription	The subscription under which you'll create your new function app.
   Resource Group	myResourceGroup	Name for the new resource group in which you'll create your function app. You should create a new resource group because there are known limitations when creating new function apps in an existing resource group.
   Function App name	Globally unique name	Name that identifies your new function app. Valid characters are a-z (case insensitive), 0-9, and -.
   Publish	Code	Option to publish code files or a Docker container.
   Runtime stack	Preferred language	Choose a runtime that supports your favorite function programming language. In-portal editing is only available for JavaScript, PowerShell, TypeScript, and C# script. C# class library, Java, and Python functions must be developed locally.
   Version	Version number	Choose the version of your installed runtime.
   Region	Preferred region	Select a region that's near you or near other services that your functions can access.

4. Select Next : Hosting. On the Hosting page, enter the following settings:

   Setting	Suggested value	Description
   Storage account	Globally unique name	Create a storage account used by your function app. Storage account names must be between 3 and 24 characters in length and can contain numbers and lowercase letters only. You can also use an existing account, which must meet the storage account requirements.
   Operating system	Windows	An operating system is pre-selected for you based on your runtime stack selection, but you can change the setting if necessary. In-portal editing is only supported on Windows.
   Plan	Consumption (Serverless)	Hosting plan that defines how resources are allocated to your function app. In the default Consumption plan, resources are added dynamically as required by your functions. In this serverless hosting, you pay only for the time your functions run. When you run in an App Service plan, you must manage the scaling of your function app.

5. Select Next : Monitoring. On the Monitoring page, enter the following settings:

   Setting	Suggested value	Description
   Application Insights	Default	Creates an Application Insights resource of the same App name in the nearest supported region. By expanding this setting or selecting Create new, you can change the Application Insights name or select a different region in an Azure geography where you want to store your data.

6. Select Review + create to review the app configuration selections.

7. On the Review + create page, review your settings, and then select Create to provision and deploy the function app.

8. Select the Notifications icon in the upper-right corner of the portal and watch for the Deployment succeeded message.

9. Select Go to resource to view your new function app. You can also select Pin to dashboard. Pinning makes it easier to return to this function app resource from your dashboard.

   

You've successfully created your new function app.

Next, you create a function in the new function app.

Create an Azure Blob storage triggered function

1. In your function app, select Overview, and then select + Create under Functions.

2. Under Select a template, scroll down and choose the Azure Blob Storage trigger template.

3. In Template details, configure the new trigger with the settings as specified in this table, then select Create:

   Setting	Suggested value	Description
   New Function	Unique in your function app	Name of this blob triggered function.
   Path	samples-workitems/{name}	Location in Blob storage being monitored. The file name of the blob is passed in the binding as the name parameter.
   Storage account connection	AzureWebJobsStorage	You can use the storage account connection already being used by your function app, or create a new one.

   Azure creates the Blob Storage triggered function based on the provided values.

Next, create the samples-workitems container.

Create the container

1. In your function, on the Overview page, select your resource group.

   

2. Find and select your resource group's storage account.

   

3. Choose Containers, and then choose + Container.

   

4. In the Name field, type samples-workitems, and then select Create.

   

Now that you have a blob container, you can test the function by uploading a file to the container.

Test the function

1. Back in the Azure portal, browse to your function expand the Logs at the bottom of the page and make sure that log streaming isn't paused.

   

2. In a separate browser window, go to your resource group in the Azure portal, and select the storage account.

3. Select Containers, and then select the samples-workitems container.

   

4. Select Upload, and then select the folder icon to choose a file to upload.

   

5. Browse to a file on your local computer, such as an image file, choose the file. Select Open and then Upload.

6. Go back to your function logs and verify that the blob has been read.

   

   Note

   When your function app runs in the default Consumption plan, there may be a delay of up to several minutes between the blob being added or updated and the function being triggered. If you need low latency in your blob triggered functions, consider running your function app in an App Service plan.

Clean up resources

Other quickstarts in this collection build upon this quickstart. If you plan to work with subsequent quickstarts, tutorials, or with any of the services you've created in this quickstart, don't clean up the resources.

Resources in Azure refer to function apps, functions, storage accounts, and so forth. They're grouped into resource groups, and you can delete everything in a group by deleting the group.

You've created resources to complete these quickstarts. You might be billed for these resources, depending on your account status and service pricing. If you don't need the resources anymore, here's how to delete them:

1. In the Azure portal, go to the Resource group page.

   To get to that page from the function app page, select the Overview tab, and then select the link under Resource group.

   

   To get to that page from the dashboard, select Resource groups, and then select the resource group that you used for this article.

2. In the Resource group page, review the list of included resources, and verify that they're the ones you want to delete.

3. Select Delete resource group and follow the instructions.

   Deletion might take a couple of minutes. When it's done, a notification appears for a few seconds. You can also select the bell icon at the top of the page to view the notification.

Next steps

You have created a function that runs when a blob is added to or updated in Blob storage. For more information about Blob storage triggers, see Azure Functions Blob storage bindings.

Now that you've created your first function, let's add an output binding to the function that writes a message to a Storage queue.