How to successfully migrate Azure Function Apps to use deployment slots

Question

Hi everyone,

Our Azure Functions Apps currently don't use deployment slots and we're looking at migrating our function apps to use them.

If we create deployment slots and then deploy updated code to the slots, what will happen to the original function app? Will it still function with all the relevant settings?

We have applications that link to the original function app name, and since the deployment slot will have a different hostname, we may have issues with production traffic not being routed to the relevant deployment slot etc.

Regards

Chris.

Answer 1

Hello Chris,

Thanks for your question.

Deployment slots, are isolated environments so your original code is fine.

Yes, deployment slots get unique host names.

See below Settings that are swapped and aren't ( from the official doc): https://learn.microsoft.com/en-us/azure/azure-functions/functions-deployment-slots?tabs=azure-portal#manage-deployment-slots

You'd need to ensure DNS and routing mechanisms points to the correct hostname after a swap.

https://learn.microsoft.com/en-us/azure/app-service/app-service-web-tutorial-custom-domain?tabs=root%2Cazurecli

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