Phusion Passenger - How to run code after request has been sent to the client?

This is similar to Is there an easy way to run Garbage Collection outside of the request cycle in Passenger? , but the accepted answer is 7+ years old and recommends patching the internals of Phusion passenger itself -- not something that I'd like to do in a production environment.

Is there a better way to do this in the newer versions of Phusion Passenger? Use-cases:

• Out of band garbage collection
• Pushing request/response stats (like cache hit ratio, time taken to render views, etc) to a collectd daemon