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Durable Functions versions overview

  • Article

Durable Functions is an extension of Azure Functions and Azure WebJobs that lets you write stateful functions in a serverless environment. The extension manages state, checkpoints, and restarts for you. If you aren't already familiar with Durable Functions, see the overview documentation.

Microsoft.Azure.WebJobs.Extensions.DurableTask v3.x

This section introduces the new Microsoft.Azure.WebJobs.Extensions.DurableTask v3 package (referred to as WebJobs.Extensions.DurableTask in subsequent sections) and provides details on its updates and changes. This update is only considered a breaking-change for customers running Durable C# apps that use the in-process model.

Note

The Durable Functions .NET out-of-process package, Microsoft.Azure.Functions.Worker.Extensions.DurableTask, references Microsoft.Azure.WebJobs.Extensions.DurableTask as its underlying assembly. Thus, this update also applies to Microsoft.Azure.Functions.Worker.Extensions.DurableTask, starting from version 1.2.x.

New Azure Storage SDK

By default, Durable Functions use Azure Storage as a storage backend to durably save application state. In WebJobs.Extensions.DurableTask v3, the Azure Storage backend was upgraded to use the latest versions of the Azure Storage SDKs: Azure.Data.Tables, Azure.Storage.Blobs, and Azure.Storage.Queues. The new Azure Storage SDKs are more secured and offer enhanced support for Managed Identity. They also offer better performance, more efficient data handling, and other latest storage features.

Improved cost efficiency for the Azure Storage backend

In the Azure Storage backend, the Partition Manager is responsible for distributing partitions/control queues among workers. The WebJobs.Extensions.DurableTask v3 package uses Partition Manager V3 by default, which is a new design that leverages Azure Tables to manage partition assignments instead of Azure Blob leases. This design can significantly reduce storage costs while making debugging easier. When Partition Manager V3 is used, a new table, named Partitions, is created in your storage account, allowing you to easily check the partition information.

Removed support for the Functions v1 runtime

WebJobs.Extensions.DurableTask v3 no longer supports version 1.x of the Azure Functions runtime, support for which is scheduled to end in September 2026. If you must use Functions runtime v1, please use a Durable Functions extension version lower than v2.11.0. Keep in mind that when the scheduled end of support comes, Durable Functions will drop its support for runtime v1 as well.

.NET Framework Update

WebJobs.Extensions.DurableTask v3 updates the .NET framework from .NET Core 3.1 to .NET 6, offering improved performance and enhanced compatibility with modern .NET features and libraries. This update aligns with future releases of the Azure Functions extension bundles.

Migration from WebJobs.Extensions.DurableTask v2.x to v3.x

Migration from WebJobs.Extensions.DurableTask v2.x to v3.x is designed to be straightforward with no code changes required, as the changes are in the background. Simply update your dependencies to start taking advantage of the new features and improvements in v3.x.

Note

WebJobs.Extensions.DurableTask v3 uses the latest version of the Azure Storage SDK, which has a different text encoding (Base64) when compared to the one used in v2 (UTF-8). If you need to downgrade from v3.x to v2.x, to ensure backward compatibility, use at least v2.13.5. For .NET out-of-process users with Microsoft.Azure.Functions.Worker.Extensions.DurableTask, downgrade to v1.1.5 or higher if reverting from v1.2.x or higher.

Support and Maintenance of v2.x

WebJobs.Extensions.DurableTask v2.x continues to receive security updates and bug fixes, ensuring that your existing applications remain secure and stable. However, all new features and enhancements are added exclusively to v3.x. Because of this, you should upgrade to WebJobs.Extensions.DurableTask v3 as soon as you can to take advantage of the latest capabilities and ongoing improvements.

New features in Microsoft.Azure.WebJobs.Extensions.DurableTask v2.x

This section describes the features of Durable Functions that are added in version 2.x.

Note

This section does not apply to Durable Functions in dotnet isolated worker. For that, see durable functions isolated process overview.

Durable entities

In Durable Functions 2.x, we introduced a new entity functions concept.

Entity functions define operations for reading and updating small pieces of state, known as durable entities. Like orchestrator functions, entity functions are functions with a special trigger type, entity trigger. Unlike orchestrator functions, entity functions don't have any specific code constraints. Entity functions also manage state explicitly rather than implicitly representing state via control flow.

To learn more, see the durable entities article.

Durable HTTP

In Durable Functions 2.x, we introduced a new Durable HTTP feature that allows you to:

  • Call HTTP APIs directly from orchestration functions (with some documented limitations).
  • Implement automatic client-side HTTP 202 status polling.
  • Built-in support for Azure Managed Identities.

To learn more, see the HTTP features article.

Migrate from 1.x to 2.x

This section describes how to migrate your existing version 1.x Durable Functions to version 2.x to take advantage of the new features.

Upgrade the extension

Install the latest 2.x version of the Durable Functions bindings extension in your project.

JavaScript, Python, and PowerShell

Durable Functions 2.x is available starting in version 2.x of the Azure Functions extension bundle.

Python support in Durable Functions requires Durable Functions 2.x or greater.

To update the extension bundle version in your project, open host.json and update the extensionBundle section to use version 4.x ([4.*, 5.0.0)).

JSON 
{
    "version": "2.0",
    "extensionBundle": {
        "id": "Microsoft.Azure.Functions.ExtensionBundle",
        "version": "[4.*, 5.0.0)"
    }
}

Note

If Visual Studio Code is not displaying the correct templates after you change the extension bundle version, reload the window by running the Developer: Reload Window command (Ctrl+R on Windows and Linux, Command+R on macOS).

Java

Durable Functions 2.x is available starting in version 4.x of the Azure Functions extension bundle. You must use the Azure Functions 4.0 runtime to execute Java functions.

To update the extension bundle version in your project, open host.json and update the extensionBundle section to use version 4.x ([4.*, 5.0.0)).

JSON 
{
    "version": "2.0",
    "extensionBundle": {
        "id": "Microsoft.Azure.Functions.ExtensionBundle",
        "version": "[4.*, 5.0.0)"
    }
}

.NET

Update your .NET project to use the latest version of the Durable Functions bindings extension.

See Register Azure Functions binding extensions for more information.

Update your code

Durable Functions 2.x introduces several breaking changes. Durable Functions 1.x applications aren't compatible with Durable Functions 2.x without code changes. This section lists some of the changes you must make when upgrading your version 1.x functions to 2.x.

Host.json schema

Durable Functions 2.x uses a new host.json schema. The main changes from 1.x include:

  • "storageProvider" (and the "azureStorage" subsection) for storage-specific configuration.
  • "tracing" for tracing and logging configuration.
  • "notifications" (and the "eventGrid" subsection) for Event Grid notification configuration.

See the Durable Functions host.json reference documentation for details.

Default task hub name changes

In version 1.x, if a task hub name wasn't specified in host.json, it was defaulted to "DurableFunctionsHub". In version 2.x, the default task hub name is now derived from the name of the function app. Because of this, if you haven't specified a task hub name when upgrading to 2.x, your code will be operating with new task hub, and all in-flight orchestrations will no longer have an application processing them. To work around this, you can either explicitly set your task hub name to the v1.x default of "DurableFunctionsHub", or you can follow our zero-downtime deployment guidance for details on how to handle breaking changes for in-flight orchestrations.

Public interface changes (.NET only)

In version 1.x, the various context objects supported by Durable Functions have abstract base classes intended for use in unit testing. As part of Durable Functions 2.x, these abstract base classes are replaced with interfaces.

The following table represents the main changes:

1.x 2.x
DurableOrchestrationClientBase IDurableOrchestrationClient or IDurableClient
DurableOrchestrationContext or DurableOrchestrationContextBase IDurableOrchestrationContext
DurableActivityContext or DurableActivityContextBase IDurableActivityContext
OrchestrationClientAttribute DurableClientAttribute

In the case where an abstract base class contained virtual methods, these virtual methods have been replaced by extension methods defined in DurableContextExtensions.

function.json changes

In Durable Functions 1.x, the orchestration client binding uses a type of orchestrationClient. Version 2.x uses durableClient instead.

Raise event changes

In Durable Functions 1.x, calling the raise event API and specifying an instance that didn't exist resulted in a silent failure. Starting in 2.x, raising an event to a non-existent orchestration results in an exception.