Zipkin exporter and collector do not agree on wire representation of status codes

[mterwill]

Description

The Zipkin exporter and collector do not agree on wire representation of status codes. Please let me know if this issue should be filed in open-telemetry/opentelemetry-collector-contrib instead.

The Zipkin exporter serializes status codes as Unset, Error, and Ok:

opentelemetry-go/exporters/zipkin/model.go

Lines 211 to 213 in 5568a30

	if data.Status().Code != codes.Unset {
	m["otel.status_code"] = data.Status().Code.String()
	}

opentelemetry-go/codes/codes.go

Lines 38 to 42 in d616df6

	var codeToStr = map[Code]string{
	Unset: "Unset",
	Error: "Error",
	Ok: "Ok",
	}

However, the collector expects STATUS_CODE_UNSET, STATUS_CODE_OK, or STATUS_CODE_ERROR, see here.

Environment

opentelemetry-go v1.11.0
opentelemetry-collector-contrib v0.62.0

Steps To Reproduce

Using Grafana Tempo's local example:

package main

import (
	"context"
	"log"

	"go.opentelemetry.io/otel"
	"go.opentelemetry.io/otel/codes"
	"go.opentelemetry.io/otel/exporters/zipkin"
	sdktrace "go.opentelemetry.io/otel/sdk/trace"
)

func main() {
	ctx := context.Background()

	exporter, err := zipkin.New("")
	if err != nil {
		log.Fatalf("creating exporter: %s", err)
	}

	tp := sdktrace.NewTracerProvider(
		sdktrace.WithSampler(sdktrace.AlwaysSample()),
		sdktrace.WithBatcher(exporter),
	)
	defer tp.Shutdown(ctx)
	otel.SetTracerProvider(tp)

	_, span := otel.Tracer("foo").Start(ctx, "foo")
	log.Printf("trace ID: %s", span.SpanContext().TraceID())
	span.SetStatus(codes.Error, "something went wrong")
	span.End()
}

Expected behavior

Status is correctly passed between exporter and collector.

[MrAlias]

Based on the specification the status value should be the ...

Name of the code, either OK or ERROR. MUST NOT be set if the code is UNSET.

It seems like we are not correctly setting it to an upper case value, but it also seems like the collector is incorrectly expecting it to be one of STATUS_CODE_UNSET, STATUS_CODE_OK, or STATUS_CODE_ERROR. I think fixes need to be applied on both sides.

[MrAlias]

@mterwill can you open an issue with the collector as well to track this parsing error?