Azure Durable Functions

Durable Functions scales as needed and provides a cost-effective means of implementing complex workflows in the cloud. Some benefits of using Durable Functions include:

• They enable you to write event-driven code. A durable function can wait asynchronously for one or more external events and then perform a series of tasks in response to these events.
• You can chain functions together. You can implement common patterns such as fan-out/fan-in, which uses one function to invoke others in parallel, and then accumulate the results.
• You can orchestrate and coordinate functions and specify the order in which functions should execute.
• The state is managed for you. You don't have to write your own code to save state information for a long-running function.

You can use three durable function types: Client, Orchestrator, and Activity.

• Client functions are the entry point for creating an instance of a Durable Functions orchestration. They can run in response to an event from many sources, such as a new HTTP request arriving, a message being posted to a message queue, an event arriving in an event stream. You can write them in any of the supported languages.
• Orchestrator functions describe how actions are executed and the order in which they are run. You write the orchestration logic in code (C# or JavaScript).
• Activity functions are the basic units of work in a durable function orchestration. An activity function contains the actual work performed by the tasks being orchestrated.