durable functions

Durable Functions: Fan Out Fan In Patterns

This post is a collaboration between myself and my awesome coworker, Maxime Rouiller.

Durable Functions? Wat. If you’re new to Durable, I suggest you start here with this post that covers all the essentials so that you can properly dive in. In this post, we’re going to dive into one particular use case so that you can see a Durable Function pattern at work!

Today, let’s talk about the Fan Out, Fan In pattern. We’ll do so by retrieving an open issue count from GitHub and then storing what we get. Here’s the repo where all the code lives that we’ll walk through in this post.

View Repo


What are Durable Functions?

Oh no! Not more jargon! What exactly does the term Durable Functions mean? Durable functions have to do with Serverless architectures. It’s an extension of Azure Functions that allow you to write stateful executions in a serverless environment.

Think of it this way. There are a few big benefits that people tend to focus on when they talk about Serverless Functions:

  • They’re cheap
  • They scale with your needs (not necessarily, but that’s the default for many services)
  • They allow you to write event-driven code