[bug] Tracing Custom Sampler ShouldSample Execute Before Custom Propagator

[yehaotian]

Package

OpenTelemetry

Package Version

Package Name	Version
OpenTelemetry.Api	1.12.0
OpenTelemetry	1.12.0
TBD	TBD

Runtime Version

net8.0

Description

Tracing Custom Sampler ShouldSample Execute Before Custom Propagator

Steps to Reproduce

steps to reproduce

.SetSampler(new ParentBasedSampler(
                        rootSampler: new CustomSampler(samplingRate)
                        ))

...

var propagators = new List<TextMapPropagator>
        {
            new TestContextPropagator(),
            new BaggagePropagator(),
            new CustomPropagator(),
        };

        Sdk.SetDefaultTextMapPropagator(new CompositeTextMapPropagator(propagators));

Add logs in the CustomSampler and CustomPropagator and you can see CustomSampler.ShouldSample run before CustomPropagator.

Expected Result

All propagator should run before Sampler so that we can use propagated info in SamplingParameters to do advanced sampling logic

Actual Result

Add logs in the CustomSampler and CustomPropagator and you can see CustomSampler.ShouldSample run before CustomPropagator.

Additional Context

No response

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[cijothomas]

AFAICT, OTel SDK never calls the propagators. It provides the ability to set/get propagators, but it never calls the propagators themselves. It's either called by user code, or instrumentation libraries. You'd need to share a minimal repro application to know more.

(Also, .NET's propagators part of a bit messy due to runtime also offering similar concept. Its a known issue #5667 (comment)). However, this is unlikely to be the culprit in this issue, but need to see minimal repro.