Azure Function Proxies for Response Header API Version and API Path Version

In my Azure Function project I had two problems:

  1. I wanted my Azure Functions to have a path with v1 in it
  2. I wanted to always return a response header with a version identifier

Here’s how I solved.

Response Header Version Info

Let’s say you want to return an API version in the response header. The response header could be something like this below.

[caption id="attachment_4740” align="aligncenter” width="618”]2018-08-06_21-12-53.png spl-version: 2018-08-03[/caption]

If we were using ASP.NET Core we could write a piece of middleware to return this. With Azure Functions we don’t have this full framework goodness but we do have a useful tool: Proxies.

You can edit the proxies via the web UI or locally, if you have a local project. If it’s the latter you need a proxies.json file at the root of your project.

The key piece is line 10. What we’re doing is setting a response override. In other words: always return this. In my case I choose to return a date. You can enter whatever you like.

Version Number in Path

By default Azure Functions will give you a URL line this:

I wanted it to have a version number in the path. I want something like this:

To do this, I need to two things:

  1. Define a route. You can see it in line 6. What this is saying it “anything ending with /api/v1/” send it to the path at line 8. The value {*restOfPath} is a variable
  2. Line 8 has the destination. I’m saying: “take whatever was after v1 and put it here.

Note how I am using https://localhost. Using this means I can avoid a round trip to my destination URL.

Voila - all done!