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

  • Article

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

Note

In-portal editing is only supported for JavaScript, PowerShell, and C# Script functions. Python in-portal editing is supported only when running in the Consumption plan. When possible, you should develop your functions locally.

To learn more about the limitations on editing function code in the Azure portal, see Development limitations in the Azure portal.

Prerequisites

  • An Azure subscription. If you don't have one, create a free account 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 create your new function app.
    Resource Group myResourceGroup Name for the new resource group in which you 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 -.
    Do you want to deploy code or container image? 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, Python, TypeScript, and C# script. C# class library and Java 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.
    Operating system Windows An operating system is preselected for you based on your runtime stack selection, but you can change the setting if necessary. In-portal editing is only supported on Windows. Container publishing is only supported on Linux.
    Hosting options and plans 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. Premium plan also offers dynamic scaling. When you run in an App Service plan, you must manage the scaling of your function app.

  4. Accept the default options of creating a new storage account on the Storage tab and a new Application Insight instance on the Monitoring tab. You can also choose to use an existing storage account or Application Insights instance.

  5. Select Review + create to review the app configuration you chose, and then select Create to provision and deploy the function app.

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

  7. 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.

    Screenshot of deployment notification.

You've successfully created your new function app.

Function app successfully created.

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.

    Select your Azure portal resource group.

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

    Access the storage account.

  3. Choose Containers, and then choose + Container.

    Add container to your storage account in the Azure portal.

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

    Name the storage container.

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.

    Expand the log in the Azure portal.

  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.

    Go to your samples-workitems container in the Azure portal.

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

    Upload a file to the blob container.

  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.

    View message in the logs.

    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.

    Screenshot that shows select the resource group to delete from the function app page.

    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.

Add messages to an Azure Storage queue using Functions