[tmd83]

By traditional APM I primarily meant stacktrace sampling based monitoring of applications.

As for overhead of tracing I wanted roughly compare (obviously it depends on the application a lot) stacktrace sampling vs. tracing based one. Are they usually of similar overhead or say tracing is lighter?

I was thinking tail based sampling could be a lot more expensive because say a head based sampling is doing trace for 10% request whereas regardless of how many sample are kept a tail based one is dong 100% trace. So tracing overhead would be much higher right?

I'm not sure why head based sampling is being called accurate in your doc? Isn't it the least accurate in a sense that it's purely statistical and rare outlier like latency spike or error could be missed?

And yes obviously a tail based sampling has to be something like (trace 5% random request or 1 every five + any outlier that gets calculated based on the captured trace)/