I have always preferred the library approach myself, but it seems like people are converging on "sidecar" proxies to connect up their microservices. Istio and Linkerd are the big ones. Istio uses Envoy which you can use without a whole "service mesh" to add things like circuit breaking, load balancing, rate limiting, etc.
Even though it seems it is no longer maintained, the circuit breakers, fail over modes and all that are well documented.
And I don't know why Hystrix hasn't been adopted by a wide audience yet. It seems like a necessity in the micro service landscape.