metadata_supplier.go

// Copyright The OpenTelemetry Authors
// SPDX-License-Identifier: Apache-2.0

package otelgrpc // import "go.opentelemetry.io/contrib/instrumentation/google.golang.org/grpc/otelgrpc"

import (
	"context"

	"go.opentelemetry.io/otel/propagation"
	"google.golang.org/grpc/metadata"
)

type metadataSupplier struct {
	metadata metadata.MD
}

// assert that metadataSupplier implements the TextMapCarrier interface.
var _ propagation.TextMapCarrier = metadataSupplier{}

func (s metadataSupplier) Get(key string) string {
	values := s.metadata.Get(key)
	if len(values) == 0 {
		return ""
	}
	return values[0]
}

func (s metadataSupplier) Set(key, value string) {
	s.metadata.Set(key, value)
}

func (s metadataSupplier) Keys() []string {
	out := make([]string, 0, len(s.metadata))
	for key := range s.metadata {
		out = append(out, key)
	}
	return out
}

func inject(ctx context.Context, propagators propagation.TextMapPropagator) context.Context {
	md, ok := metadata.FromOutgoingContext(ctx)
	if !ok {
		md = metadata.MD{}
	}
	propagators.Inject(ctx, metadataSupplier{
		metadata: md,
	})
	return metadata.NewOutgoingContext(ctx, md)
}

func extract(ctx context.Context, propagators propagation.TextMapPropagator) context.Context {
	md, ok := metadata.FromIncomingContext(ctx)
	if !ok {
		md = metadata.MD{}
	}

	return propagators.Extract(ctx, metadataSupplier{
		metadata: md,
	})
}