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> The worst part about tracing is sprinkling the tracing code in all the places you need it.

On the JVM this is usually done by agents that automatically attach to your process, you don't have to instrument your code at all. I think Datadog open-sourced their implementation?

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Java Flight Recorder is basically 0 overhead as well and built directly into the VM.

Isn't Flight Recorder profiling and not tracing? Or has this been added?

Both JFR and agent based implementations only work with non async code. As soon as you do async anything, stack traces are no longer representative so automatic instrumentation is useless.

That said, I’m really hoping Project Loom will fix that issue by getting rid of most async callback-style I/O.

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