Service creation states

This may be a FAQ, but is there a state diagram and/or description of the states a 1.12 service goes through on startup? The documentation for “service ps” describes the desired states (I’m not actually sure what “accepted” means, btw) but not the possible current states. Specifically I have a service which appears to be stuck “Allocating” a resource and would like to know how best to determine what is happening.