Understanding the various OperationContext.Stage values, and what should/should not be done in those stages, is important for doing things properly.

Having some javadoc noting what stages various methods will be called will help a bit. The old school stuff wildfly-subsystem replaces wasn't great about that either, but it was somewhat apparent via things like 'performRuntime' as a method name.

The specific thing that comes to mind is ResourceServiceConfigurator.configure.