Monday 1 July 2019

Deploying Azure Function Proxies along with Function Apps

I am working with Azure Function Proxies in my latest project and I have found them to be a really handy tool! With Function Proxies, we can expose endpoints in a Functions App which redirect to other resources in Azure (or anywhere really).

I won't go into much detail describing Proxies, Microsoft docs has some great info already:

"With proxies, you can specify endpoints on your function app that are implemented by another resource. You can use these proxies to break a large API into multiple function apps (as in a microservice architecture), while still presenting a single API surface for clients."

In my case, we are working on a front-end app built using TypeScript and React which uses Azure Functions as the back-end. For hosting the front-end, we have turned on the static website hosting for blob storage and then placed the HTML, JS and CSS files in it. Then, used Azure Function Proxies to redirect the endpoints in the Function App to the blob storage URLs of the front-end resources. It's all working quite nicely!

Only speed-bump in this type of architecture is the cold start experienced by serverless resources on the consumption plan. This is not a problem for us right now because this application is a proof of concept for a larger project. (There are other options available as well which include moving the Function App to an App Service Plan or using the Azure Functions Premium plan when it comes out preview. But that is a discussion for another time)

Back to the current post! When I was looking into deploying this application as part of the CI/CD pipeline using Azure DevOps, I was looking for an easy way to deploy the Azure Function Proxy configuration as well. Fortunately, I came across this Microsoft docs article which talks about a file called proxies.json. If this file is found within your Function App, the functions runtime reads it and creates the necessary proxies!

Here is how my proxies.json file looks in Visual Studio. Make sure the file is copied to the output directory:

And once the Functions App is deployed:

This way, if you are deploying and recreating Function Apps with your CI/CD pipeline, you can automate the creation of Function Proxies as well!

Hope you found this post useful.