Run your functions from a package file in Azure

In Azure, you can run your functions directly from a deployment package file in your function app. The other option is to deploy your files in the d:\home\site\wwwroot (Windows) or /home/site/wwwroot (Linux) directory of your function app.

This article describes the benefits of running your functions from a package. It also shows how to enable this functionality in your function app.

Benefits of running from a package file

There are several benefits to running from a package file:

  • Reduces the risk of file copy locking issues.
  • Can be deployed to a production app (with restart).
  • You can be certain of the files that are running in your app.
  • Improves the performance of Azure Resource Manager deployments.
  • May reduce cold-start times, particularly for JavaScript functions with large npm package trees.

For more information, see this announcement.

Enable functions to run from a package

To enable your function app to run from a package, add a WEBSITE_RUN_FROM_PACKAGE setting to your function app settings. The WEBSITE_RUN_FROM_PACKAGE setting can have one of the following values:

Value Description
1 Indicates that the function app runs from a local package file deployed in the d:\home\data\SitePackages (Windows) or /home/data/SitePackages (Linux) folder of your function app.
<URL> Sets a URL that is the remote location of the specific package file you want to run. Required for functions apps running on Linux in a Consumption plan.

The following table indicates the recommended WEBSITE_RUN_FROM_PACKAGE options for deployment to a specific operating system and hosting plan:

Hosting plan Windows Linux
Consumption 1 is highly recommended. Only <URL> is supported.
Premium 1 is recommended. 1 is recommended.
Dedicated 1 is recommended. 1 is recommended.

General considerations

  • The package file must be .zip formatted. Tar and gzip formats aren't currently supported.
  • Zip deployment is recommended.
  • When deploying your function app to Windows, you should set WEBSITE_RUN_FROM_PACKAGE to 1 and publish with zip deployment.
  • When you run from a package, the wwwroot folder becomes read-only and you'll receive an error when writing files to this directory. Files are also read-only in the Azure portal.
  • The maximum size for a deployment package file is currently 1 GB.
  • You can't use local cache when running from a deployment package.
  • If your project needs to use remote build, don't use the WEBSITE_RUN_FROM_PACKAGE app setting. Instead add the SCM_DO_BUILD_DURING_DEPLOYMENT=true deployment customization app setting. For Linux, also add the ENABLE_ORYX_BUILD=true setting. To learn more, see Remote build.

Note

WEBSITE_RUN_FROM_PACKAGE does not work with MSDeploy as described here. You will receive an error during deployment like ARM-MSDeploy Deploy Failed. Change /MSDeploy to /ZipDeploy and this error will be resolved.

Adding the WEBSITE_RUN_FROM_PACKAGE setting

There are several ways that you can add, update, and delete function app settings:

Changes to function app settings require your function app to be restarted.

Using WEBSITE_RUN_FROM_PACKAGE = 1

This section provides information about how to run your function app from a local package file.

Considerations for deploying from an on-site package

  • Using an on-site package is the recommended option for running from the deployment package, except on Linux hosted in a Consumption plan.
  • Zip deployment is the recommended way to upload a deployment package to your site.
  • When not using zip deployment, make sure the d:\home\data\SitePackages (Windows) or /home/data/SitePackages (Linux) folder has a file named packagename.txt. This file contains only the name, without any whitespace, of the package file in this folder that's currently running.

Integration with zip deployment

Zip deployment is a feature of Azure App Service that lets you deploy your function app project to the wwwroot directory. The project is packaged as a .zip deployment file. The same APIs can be used to deploy your package to the d:\home\data\SitePackages (Windows) or /home/data/SitePackages (Linux) folder.

With the WEBSITE_RUN_FROM_PACKAGE app setting value of 1, the zip deployment APIs copy your package to the d:\home\data\SitePackages (Windows) or /home/data/SitePackages (Linux) folder instead of extracting the files to d:\home\site\wwwroot (Windows) or /home/site/wwwroot (Linux). It also creates the packagename.txt file. After a restart, the package is mounted to wwwroot as a read-only filesystem. For more information about zip deployment, see Zip deployment for Azure Functions.

Note

When a deployment occurs, a restart of the function app is triggered. Function executions currently running during the deploy are terminated. Please review Improve the performance and reliability of Azure Functions to learn how to write stateless and defensive functions.

Using WEBSITE_RUN_FROM_PACKAGE = URL

This section provides information about how to run your function app from a package deployed to a URL endpoint. This option is the only one supported for running from a package on Linux hosted in a Consumption plan.

Considerations for deploying from a URL

  • When running a function app on Windows, the app setting WEBSITE_RUN_FROM_PACKAGE = <URL> gives worse cold-start performance and isn't recommended.
  • When you specify a URL, you must also manually sync triggers after you publish an updated package.
  • The Functions runtime must have permissions to access the package URL.
  • You shouldn't deploy your package to Azure Blob Storage as a public blob. Instead, use a private container with a Shared Access Signature (SAS) or use a managed identity to enable the Functions runtime to access the package.
  • When running on a Premium plan, make sure to eliminate cold starts.
  • When running on a Dedicated plan, make sure you've enabled Always On.
  • You can use the Azure Storage Explorer to upload package files to blob containers in your storage account.

Manually uploading a package to Blob Storage

To deploy a zipped package when using the URL option, you must create a .zip compressed deployment package and upload it to the destination. This example deploys to a container in Blob Storage.

  1. Create a .zip package for your project using the utility of your choice.

  2. In the Azure portal, search for your storage account name or browse for it in storage accounts.

  3. In the storage account, select Containers under Data storage.

  4. Select + Container to create a new Blob Storage container in your account.

  5. In the New container page, provide a Name (for example, "deployments"), make sure the Public access level is Private, and select Create.

  6. Select the container you created, select Upload, browse to the location of the .zip file you created with your project, and select Upload.

  7. After the upload completes, choose your uploaded blob file, and copy the URL. You may need to generate a SAS URL if you aren't using an identity

  8. Search for your function app or browse for it in the Function App page.

  9. In your function app, select Configurations under Settings.

  10. In the Application Settings tab, select New application setting

  11. Enter the value WEBSITE_RUN_FROM_PACKAGE for the Name, and paste the URL of your package in Blob Storage as the Value.

  12. Select OK. Then select Save > Continue to save the setting and restart the app.

Now you can run your function in Azure to verify that deployment has succeeded using the deployment package .zip file.

The following shows a function app configured to run from a .zip file hosted in Azure Blob storage:

WEBSITE_RUN_FROM_ZIP app setting