Currently, the topology description libmongoc provides to event listeners is (a) owned by libmongoc and (b) is freed when control is returned the libmongoc. With server descriptions (provided to other SDAM events), listeners have the ability to copy/destroy those objects; however, this is not the case with topology descriptions.

PHPC-1150 needs such an API to fully implement SDAM monitoring, since its event objects may outlive the listener function.