There is not register process like eucalyptus or AWS.

As of now, the users can be created from keystone and the same user can be logged in Horizon.

are you looking for user registration function or function to be executed (like logging) when the login page is loaded?

Or a function to be run during logging in?jest before djang_login() is executed?

Are you asking how to implement a self-registration feature, or if one exists. If the latter, shausy is correct and a method integrated into Horizon does not exist. If you are asking how to implement this feature you will have a difficult time doing this without getting changes made in Keystone, as it does not currently have a method to self-register users. User creation currently requires an authenticated user.