Upstart doesn't have a formal dependency system, instead it orders things based on named preconditions and postconditions called events. Though these can be use

Upstart doesn't have a formal dependency system, instead it orders things based on named preconditions and postconditions called events. Though these can be used to fulfill ordering requirements, I'd wager the information wasn't granular enough for parallelization to be efficient. Actually the main problem is that a lot of modern systems do not make their dependency graphs well observable, but instead treat them as in-memory ephemera that are constantly recalculated and cannot e.g. be written to persistent storage as known-good checkpoints. This is one area where s6-rc gets it right. You have to compile a manifest of your service dependencies and consistently boot from that well-known state, so for any changes it must be regenerated. serel was an earlier example of a service dependency system and parallel launcher which directly had you specify the nodes and edges of a directed graph as an RDF manifest. Clever.