W3C is compatible with B3 protocol

[dino-ma]

I want to ask how to be compatible with W3C and Zipkin B3 protocol at the same time, and what should I do if W3C protocol takes precedence? I think I need an example.

B3：https://github.com/openzipkin/b3-propagation W3C：https://w3c.github.io/trace-context/ Jaeger：https://github.com/open-telemetry/opentelemetry-go-contrib/blob/main/propagators/jaeger/jaeger_propagator.go

If I can, I hope I can be compatible with these three at the same time.

reference resources: https://github.com/open-telemetry/opentelemetry-go-contrib/tree/main/propagators https://github.com/open-telemetry/opentelemetry-go/blob/main/example/passthrough/handler/handler.go https://github.com/open-telemetry/opentelemetry-go-contrib/blob/main/propagators/b3/b3_example_test.go

My code.

 import(
       "go.opentelemetry.io/contrib/propagators/b3"
    jaegerPropagators "go.opentelemetry.io/contrib/propagators/jaeger"
    "go.opentelemetry.io/otel"
    "go.opentelemetry.io/otel/attribute"
    "go.opentelemetry.io/otel/codes"
    "go.opentelemetry.io/otel/exporters/jaeger"
    "go.opentelemetry.io/otel/propagation"
    "go.opentelemetry.io/otel/sdk/resource"
    tracesdk "go.opentelemetry.io/otel/sdk/trace"
    semconv "go.opentelemetry.io/otel/semconv/v1.7.0"
    "go.opentelemetry.io/otel/trace"
)

    jaegerPropagator := jaegerPropagators.Jaeger{}
        b3Propagators := b3.New(b3.WithInjectEncoding(b3.B3MultipleHeader | b3.B3SingleHeader))
        otel.SetTextMapPropagator(propagation.NewCompositeTextMapPropagator(propagation.TraceContext{}, propagation.Baggage{}, b3Propagators, jaegerPropagator))

request Header：

• [x] B3: key: x-b3-traceid value:463ac35c9f6413ad48485a3953bb6124
• [x] Jaeger: key:uber-trace-id value:518ee099f68f3974:17531754249a513a:518ee099f68f3974:1

At present, Jaeger is OK, B3 is not.

@yurishkuro @Aneurysm9

[MrAlias]

There can only ever be one value for span context values. A span can only belong to a single trace, and that span needs to uniquely be identified.

The way a composite propagator resolves any conflicts is the last propagator wins. That is why you are decoding Jaeger values and not B3 for the trace ID. For extraction of trace data propagators should be passed in order of precedence.

For injection, all propagators of a composite propagator will inject the context. This allows downstream systems that use different context propagation protocols to understand the data.