Google App Engine: single application, multiple domains

Question

I would like to create an App Engine-based web application and use Google accounts to authenticate users. And I need users from multiple domains to be able to log in . From what I read, it seems like this cannot be done using the Google Accounts API. Why is this so? I really like the simplicity of this.

The second authentication option in the application settings is “federated login”, but it is marked as experimental, and only I could find it, this is what is connected with OpenID. Could this solve my problem?

I also found a review (actually on this server) that recommended using Marketplace applications. Firstly, I was very excited about this because I thought the App Marketplace would create a separate instance of my application for each paid domain. But I tried one app engine based on App Engine, and it seems to me that all Marketplace does is a simple redirect, and I have to take care of authentication (perhaps the “federated login” mentioned). Thus, again, it is not possible to use the simplicity of the Google Accounts API. Or am I wrong?

Answer 1

Well, since no one answered my question, I have to do it myself :)

I spent many hours reading Google documentation, and I came to the conclusion that the Marketplace app would be the best solution for me. Marketplace apps use SSO to authenticate users who are referred to as “federated logins.” I found a few usage examples in the documentation, and in fact it is quite simple. I just don’t understand why it is marked as experimental. The downside is that users with a standard Google account will not be able to log in, but this is not a priority. The good thing, on the other hand, is that App Engine provides the Namespaces API. Using this API, you can actually create a separate instance for each domain from which I originally hoped.