[necubi]

Yeah, that's definitely an upside of the dapper approach--very, very minimal overhead for non-traced requests. However for the vast majority of use cases a bit of overhead (microseconds per span) tends to be unnoticeable, and the benefits in terms of introspectability are huge. In general, the overhead is mitigated by the fact that spans tend to be pretty large (on the ms-scale).

[ehsankia]

I guess it depends on your use case. If you are indeed interested in the 99p latency, then yes, the only way would be to trace everything. But in that case, couldn't you temporarily set the Dapper probability to 100%, record the data you need, and then turn it back down. It seems like a lot more malleable for different use cases.