[Sampling]: Example needed for ParentBased sampler with the TraceIDRatioBased sampler

[JRobTS]

URL

https://opentelemetry.io/docs/languages/go/sampling/

Description

The last statement in the document is unclear. It's not clear how to use the ParentBased sampler with the TraceIDRatioBased sampler.

An example would be handy.

I'm guessing here but to setup a 1% sampler, both parent and child services would configure this:

provider := trace.NewTracerProvider(
    trace.WithSampler(trace.ParentBased(trace.WithRemoteParentSampled(trace.TraceIDRatioBased(.01)))),
)

Or, is it more like this?

// In parent application:
provider := trace.NewTracerProvider(
    trace.WithSampler(trace.TraceIDRatioBased(.01)),
)

// In child application
provider := trace.NewTracerProvider()

Do we need to apply the same sampler to both?

// In parent application:
provider := trace.NewTracerProvider(
    trace.WithSampler(trace.TraceIDRatioBased(.01)),
)

// In child application
provider := trace.NewTracerProvider(
    trace.WithSampler(trace.ParentBased(trace.TraceIDRatioBased(.01))),
)

[tiffany76]

Thanks for providing feedback and seeking clarification, @JRobTS!

@open-telemetry/go-approvers, PTAL.

[cartermp]

You need to configure sampling for each application in exactly the same way, yes.

I'd recommend, if doing head sampling like this, to use environment variables instead.