Azure Functions extension bundles

This article explains how extension bundles enable your function code use all of the triggers and bindings supported by Azure Functions. You also learn about the various support levels and policies for your apps when using extension bundles.

This article applies only to Azure Functions developers using non-.NET languages. To learn how to add binding extensions directly to your C# function apps, see Register Azure Functions binding extensions.

Overview

Extension bundles adds a predefined set of compatible binding extensions to your function app. Extension bundles are versioned. Each version contains a specific set of binding extensions that are verified to work together. Select a bundle version based on the versions of the extensions that you need in your app.

When you create an Azure Functions project from a non-.NET template, extension bundles are already enabled in the app's host.json file.

Define an extension bundle reference

You define an extension bundle reference in the host.json project file by adding an extensionBundle section, as in this example:

{
    "version": "2.0",
    "extensionBundle": {
        "id": "Microsoft.Azure.Functions.ExtensionBundle",
        "version": "[4.0.0, 5.0.0)"
    }
}

The following properties are available in extensionBundle:

Supported extension bundles

This table lists all Microsoft.Azure.Functions.ExtensionBundle bundle versions and the current support state.

The default extension bundles are defined using version ranges. Select the Bundle version to see the extensions.json definition file used to generate the current major extension bundle version.

For more information, see Support policy.

Extension bundles considerations

Keep these considerations in mind when working with extension bundles:

• When possible, you should set a version range value in host.json from this table, such as [4.0.0, 5.0.0), instead of defining a custom range.
• Use the latest version range to obtain optimal app performance and access to the latest features.
• In the unlikely event you can't use an extension bundle, you must instead explicitly install extensions.

Preview extension bundles

Prerelease versions of specific binding extensions are made maintained in a preview extension bundle. The preview extension bundle (Microsoft.Azure.Functions.ExtensionBundle.Preview) allows you to take advantage of preview extensions and new behaviors in existing extensions before they're declared as GA.

Keep these considerations in mind when choosing to use a non-GA extension bundle:

• Preview bundles can include features that are still under development and not yet ready for production use. They're intended for evaluation and testing in nonproduction environments.
• Breaking changes occur between preview versions without prior notice, which can include changes to:
  • Trigger and binding definitions
  • Extensions included in the preview
  • Performance characteristics and stability
• Security updates might require you to upgrade versions.
• You must completely test preview bundles in nonproduction environments and avoid using preview bundles in production. When you must use a preview bundle in production, take these extra precautions:
  • Pin your bundle to a specific well-tested bundle version instead of to a range. Pinning prevents automatic upgrading of your bundle version before you have a chance to verify the update in a nonproduction environment.
  • Move your app to using a GA bundle version as soon as the functionality becomes available in a fully supported bundle release.
• To stay informed about bundle updates, including moving from preview to GA, you should:
  • Monitor preview bundle version releases on the extension bundles release page. - Releases · Azure/azure-functions-extension-bundles
  • Monitor extension specific reference documentation.
  • Review the NuGet package versions of specific preview extensions you're using.
  • Track significant updates or changes on the change logs published on NuGet.org for each preview extension.

Support policy 

Major version releases of extension bundles can occur when there are breaking changes or updates in the dependencies of the underlying binding extensions. These breaking changes, often introduced in Azure SDKs, require updates to the bundle to remain compatible.

The support cycle of a GA extension bundle follows these distinct phases:

You can view the extension bundle versions and their included extensions in the Azure Functions Extension Bundles GitHub repo. Individual .NET packages are found on https://nuget.org.

Related articles

To learn more about binding extensions, see Register Azure Functions binding extensions.