Q:

In which case, authorization key of azure function will change?

I am working my first Azure function with http trigger. code are stored in TFS, our release team will deploy it use octopus. 
my question is in which situation, authorization key of azure function will change?
remove function app? delete function? any other case? 
Thanks, 
Wes

A:

my question is in which situation, authorization key of azure function will change? remove function app? delete function? any other case?

If you metioned authorization key is authorization code for http trigger. There are 2 types of keys (API Keys and Master key) for the http tigger function.
API Keys:

Function App Level keys means that all of specific function are the same for the current app. (Unless delete the function app, the key will changed/not exist)

Function level keys apply to the specific functions(Delete the specific functions, it will change)

Host: Also commonly referred to as Function App Level keys. Keys defined at this level apply to the entire Function App. You have the ability to define Function Keys at this level, and they would allow clients to authenticate against any function. This is also where your Master Key is defined.

Function: Function level keys apply to the specific functions they're defined under, restricting its use for authentication to that function only.

Master Key:

The master key provides administrative access to the runtime APIs. You should exercise care if you choose to use the Admin authorization level for your functions as we do not recommend redistributing the master key.

We also could use the Rest API to change the key. For more information about Http trigger function, please refer to this document.

