Emergent Cascading Distributed Termination - Graceful shutdown for libfbp

Lets stop monkeying around with termination in FBP 

TL;DR Herein proposed Emergent Cascading Distributed Termination (ECDT) whereby the libfbp component, viewed as an isolated push down automaton(PDA)[1], either:

• Reaches its own internal accept/final state and, as part of removing itself from the execution model's purview,  closes all its connection(s).

or

• Reacts to the closed exception(s) thrown by its connections(s) and reaches its own alternative, or only in some cases, final state and, as part of removing itself from the execution model's purview,  closes all its remaining connection(s).

and so on.

Thereby gracefully, and yet unknowingly, cascading the closed connections through the program graph ensemble of components allowing each to reach their final state and spread the cascade.

In order to retain the fungibility and black-box isolation requirements of FBP a component's terminating behaviour must be both dependency inverted, from an OOP perspective, and non-cooperative from a CSP theory perspective. With these immutable axioms in hand how then might libfbp not only terminate but do so gracefully?