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package tracing
import (
"context"
"github.com/go-kratos/kratos/v2"
"github.com/go-kratos/kratos/v2/metadata"
"go.opentelemetry.io/otel/propagation"
)
const serviceHeader = "x-md-service-name"
// Metadata is tracing metadata propagator
type Metadata struct{}
var _ propagation.TextMapPropagator = Metadata{}
// Inject sets metadata key-values from ctx into the carrier.
func (b Metadata) Inject(ctx context.Context, carrier propagation.TextMapCarrier) {
app, ok := kratos.FromContext(ctx)
if ok {
carrier.Set(serviceHeader, app.Name())
}
}
// Extract returns a copy of parent with the metadata from the carrier added.
func (b Metadata) Extract(parent context.Context, carrier propagation.TextMapCarrier) context.Context {
name := carrier.Get(serviceHeader)
if name == "" {
return parent
}
if md, ok := metadata.FromServerContext(parent); ok {
md.Set(serviceHeader, name)
return parent
}
md := metadata.New()
md.Set(serviceHeader, name)
parent = metadata.NewServerContext(parent, md)
return parent
}
// Fields returns the keys who's values are set with Inject.
func (b Metadata) Fields() []string {
return []string{serviceHeader}
}