Howdy,
ocaml-trace 0.8 was just released. It features a new trace collector for multiprocess programs, and a new library, trace.subscriber, for handling events in a more modular, compositional way.
For background, trace is a lightweight library that can be used to instrument your code (libraries or executable), either by hand or using ppx_trace, and offers a collector abstraction to actually collect/handle/store/write the trace events somewhere. The overhead when no collector is installed is low. There are also several collectors in trace-tef, trace-fuchsia, and (in a separate repo) tracy-client. See the github repo for more details.