The earlier User Federation SPI required you to create a local copy of a user in the Keycloak’s database and import information from your external store to the local copy. However, this is no longer a requirement. You can still port your earlier provider as-is, but you should consider whether a non-import strategy might be a better approach.

Advantages of the import strategy:

There are some obvious disadvantages though to using an import strategy:

The first thing to notice is that UserFederationProvider was a complete interface. You implemented every method in this interface. However, UserStorageProvider has instead broken up this interface into multiple capability interfaces that you implement as needed.

UserFederationProvider.getUserByUsername() and getUserByEmail() have exact equivalents in the new SPI. The difference between the two is how you import. If you are going to continue with an import strategy, you no longer call KeycloakSession.userStorage().addUser() to create the user locally. Instead you call KeycloakSession.userLocalStorage().addUser(). The userStorage() method no longer exists.

The UserFederationProvider.validateAndProxy() method has been moved to an optional capability interface, ImportedUserValidation. You want to implement this interface if you are porting your earlier provider as-is. Also note that in the earlier SPI, this method was called every time the user was accessed, even if the local user is in the cache. In the later SPI, this method is only called when the local user is loaded from local storage. If the local user is cached, then the ImportedUserValidation.validate() method is not called at all.

The UserFederationProvider.isValid() method no longer exists in the later model.

The UserFederationProvider methods synchronizeRegistrations(), registerUser(), and removeUser() have been moved to the UserRegistrationProvider capability interface. This new interface is optional to implement so if your provider does not support creating and removing users, you don’t have to implement it. If your earlier provider had switch to toggle support for registering new users, this is supported in the new SPI, returning null from UserRegistrationProvider.addUser() if the provider doesn’t support adding users.

The earlier UserFederationProvider methods centered around credentials are now encapsulated in the CredentialInputValidator and CredentialInputUpdater interfaces, which are also optional to implement depending on if you support validating or updating credentials. Credential management used to exist in UserModel methods. These also have been moved to the CredentialInputValidator and CredentialInputUpdater interfaces. One thing to note that if you do not implement the CredentialInputUpdater interface, then any credentials provided by your provider can be overridden locally in Keycloak storage. So if you want your credentials to be read-only, implement the CredentialInputUpdater.updateCredential() method and return a ReadOnlyException.

The UserFederationProvider query methods such as searchByAttributes() and getGroupMembers() are now encapsulated in an optional interface UserQueryProvider. If you do not implement this interface, then users will not be viewable in the admin console. You’ll still be able to login though.

The synchronization methods in the earlier SPI are now encapsulated within an optional ImportSynchronization interface. If you have implemented synchronization logic, then have your new UserStorageProviderFactory implement the ImportSynchronization interface.

The User Storage SPI instances are stored in a different set of relational tables. Keycloak automatically runs a migration script. If any earlier User Federation providers are deployed for a realm, they are converted to the later storage model as is, including the id of the data. This migration will only happen if a User Storage provider exists with the same provider ID (i.e., "ldap", "kerberos") as the earlier User Federation provider.

So, knowing this there are different approaches you can take.

If you have decided to get rid of the import strategy and rewrite your User Storage provider, we suggest that you remove the earlier provider before upgrading Keycloak. This will remove linked local imported copies of any user you imported.