blob: 38f251d31a702ec4f50a89ef63c481e5c246fd18 [file] [log] [blame]
// Copyright 2017 Michal Witkowski. All Rights Reserved.
// See LICENSE for licensing terms.
package grpc_opentracing
import (
"encoding/base64"
"strings"
"fmt"
"google.golang.org/grpc/metadata"
)
const (
binHdrSuffix = "-bin"
)
// metadataTextMap extends a metadata.MD to be an opentracing textmap
type metadataTextMap metadata.MD
// Set is a opentracing.TextMapReader interface that extracts values.
func (m metadataTextMap) Set(key, val string) {
// gRPC allows for complex binary values to be written.
encodedKey, encodedVal := encodeKeyValue(key, val)
// The metadata object is a multimap, and previous values may exist, but for opentracing headers, we do not append
// we just override.
m[encodedKey] = []string{encodedVal}
}
// ForeachKey is a opentracing.TextMapReader interface that extracts values.
func (m metadataTextMap) ForeachKey(callback func(key, val string) error) error {
for k, vv := range m {
for _, v := range vv {
if decodedKey, decodedVal, err := metadata.DecodeKeyValue(k, v); err == nil {
if err = callback(decodedKey, decodedVal); err != nil {
return err
}
} else {
return fmt.Errorf("failed decoding opentracing from gRPC metadata: %v", err)
}
}
}
return nil
}
// encodeKeyValue encodes key and value qualified for transmission via gRPC.
// note: copy pasted from private values of grpc.metadata
func encodeKeyValue(k, v string) (string, string) {
k = strings.ToLower(k)
if strings.HasSuffix(k, binHdrSuffix) {
val := base64.StdEncoding.EncodeToString([]byte(v))
v = string(val)
}
return k, v
}