blob: 583025ce531cb6df1c0a97373aa4a64d1c092c00 [file] [log] [blame]
package grpc_ctxtags
import (
type ctxMarker struct{}
var (
// ctxMarkerKey is the Context value marker used by *all* logging middleware.
// The logging middleware object must interf
ctxMarkerKey = &ctxMarker{}
// NoopTags is a trivial, minimum overhead implementation of Tags for which all operations are no-ops.
NoopTags = &noopTags{}
// Tags is the interface used for storing request tags between Context calls.
// The default implementation is *not* thread safe, and should be handled only in the context of the request.
type Tags interface {
// Set sets the given key in the metadata tags.
Set(key string, value interface{}) Tags
// Has checks if the given key exists.
Has(key string) bool
// Values returns a map of key to values.
// Do not modify the underlying map, please use Set instead.
Values() map[string]interface{}
type mapTags struct {
values map[string]interface{}
func (t *mapTags) Set(key string, value interface{}) Tags {
t.values[key] = value
return t
func (t *mapTags) Has(key string) bool {
_, ok := t.values[key]
return ok
func (t *mapTags) Values() map[string]interface{} {
return t.values
type noopTags struct{}
func (t *noopTags) Set(key string, value interface{}) Tags {
return t
func (t *noopTags) Has(key string) bool {
return false
func (t *noopTags) Values() map[string]interface{} {
return nil
// Extracts returns a pre-existing Tags object in the Context.
// If the context wasn't set in a tag interceptor, a no-op Tag storage is returned that will *not* be propagated in context.
func Extract(ctx context.Context) Tags {
t, ok := ctx.Value(ctxMarkerKey).(Tags)
if !ok {
return NoopTags
return t
func setInContext(ctx context.Context, tags Tags) context.Context {
return context.WithValue(ctx, ctxMarkerKey, tags)
func newTags() Tags {
return &mapTags{values: make(map[string]interface{})}