[cschneid]

When I worked at ScoutAPM, that list is basically the exact areas where we had issues supporting. We didn't do full-on tracing in the OpenTracing kind of way, but the agent was pretty similar, with spans (mostly automatically inserted), and annotations on those spans with timing, parentage, and extra info (like the sql query this represented in Active record).

The really hard things, which we had reasonable answers for, but never quite perfect: * Rails websockets (actioncable) * very long running background jobs (we stopped collecting at some limit, to prevent unbounded memory) * trying to profile code, we used a modified version of Stackprof to do sampling instead of exact profiling. That worked surprisingly well at finding hotspots, with low overhead.

All sorts of other tricks came along too. I should go look at that codebase again to remind me. That'd be good for my resume.... :)

https://github.com/scoutapp/scout_apm_ruby