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Run your Azure Functions from a package
Have the Azure Functions runtime run your functions by mounting a deployment package file that contains your function app project files.
conceptual
07/15/2019

Run your Azure Functions from a package file

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 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.

Enabling functions to run from a package

To enable your function app to run from a package, you just 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 Recommended for function apps running on Windows. Run from a package file in the d:\home\data\SitePackages folder of your function app. If not deploying with zip deploy, this option requires the folder to also have a file named packagename.txt. This file contains only the name of the package file in folder, without any whitespace.
<URL> Location of a specific package file you want to run. When you specify a URL, you must also sync triggers after you publish an updated package.
When using Blob storage, you typically should not use 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. You can use the Azure Storage Explorer to upload package files to your Blob storage account.

Caution

When running a function app on Windows, the external URL option yields worse cold-start performance. When deploying your function app to Windows, you should set WEBSITE_RUN_FROM_PACKAGE to 1 and publish with zip deployment.

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

WEBSITE_RUN_FROM_ZIP app setting

Note

Currently, only .zip package files are supported.

Fetch a package from Azure Blob Storage using a managed identity

[!INCLUDE Run from package via Identity]

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 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 folder instead of extracting the files to d:\home\site\wwwroot. 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. Before a restart, all existing function executions are allowed to complete or time out. To learn more, see Deployment behaviors.

Adding the WEBSITE_RUN_FROM_PACKAGE setting

[!INCLUDE Function app settings]

Troubleshooting

  • Run From Package makes wwwroot read-only, so you will receive an error when writing files to this directory.
  • Tar and gzip formats are not supported.
  • The ZIP file can be at most 1GB.
  • This feature does not compose with local cache.
  • For improved cold-start performance, use the local Zip option (WEBSITE_RUN_FROM_PACKAGE=1).
  • Run From Package is incompatible with deployment customization option (SCM_DO_BUILD_DURING_DEPLOYMENT=true), the build step will be ignored during deployment.

Next steps

[!div class="nextstepaction"] Continuous deployment for Azure Functions