How to setup profiling with traces_sampler

[paxw-panevo]

In the docs, it says that

The profiles_sample_rate setting is relative to the traces_sample_rate setting.

We use a traces_sampler. Is my assumption correct that sentry can only profile what's been traced? Is it correct, then, that regardless whether we use profiles_sampler or profiles_sample_rate, it is still relative to whatever traces_sampler returns?

[antonpirker]

Yes, you are correct, profiles can be only recorded to sampled traces.

For example if you have set profiles_sample_rate=0.2 and in your traces_sampler you discard 60% of your traces, there will be profiles attached to 20% (the 0.2) of the remaining 40% of the traces that have been sampled by traces_sampler.