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// Copyright 2017, OpenCensus Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
package tag
import (
"bytes"
"context"
"fmt"
"sort"
)
// Tag is a key value pair that can be propagated on wire.
type Tag struct {
Key Key
Value string
}
type tagContent struct {
value string
m metadatas
}
// Map is a map of tags. Use New to create a context containing
// a new Map.
type Map struct {
m map[Key]tagContent
}
// Value returns the value for the key if a value for the key exists.
func (m *Map) Value(k Key) (string, bool) {
if m == nil {
return "", false
}
v, ok := m.m[k]
return v.value, ok
}
func (m *Map) String() string {
if m == nil {
return "nil"
}
keys := make([]Key, 0, len(m.m))
for k := range m.m {
keys = append(keys, k)
}
sort.Slice(keys, func(i, j int) bool { return keys[i].Name() < keys[j].Name() })
var buffer bytes.Buffer
buffer.WriteString("{ ")
for _, k := range keys {
buffer.WriteString(fmt.Sprintf("{%v %v}", k.name, m.m[k]))
}
buffer.WriteString(" }")
return buffer.String()
}
func (m *Map) insert(k Key, v string, md metadatas) {
if _, ok := m.m[k]; ok {
return
}
m.m[k] = tagContent{value: v, m: md}
}
func (m *Map) update(k Key, v string, md metadatas) {
if _, ok := m.m[k]; ok {
m.m[k] = tagContent{value: v, m: md}
}
}
func (m *Map) upsert(k Key, v string, md metadatas) {
m.m[k] = tagContent{value: v, m: md}
}
func (m *Map) delete(k Key) {
delete(m.m, k)
}
func newMap() *Map {
return &Map{m: make(map[Key]tagContent)}
}
// Mutator modifies a tag map.
type Mutator interface {
Mutate(t *Map) (*Map, error)
}
// Insert returns a mutator that inserts a
// value associated with k. If k already exists in the tag map,
// mutator doesn't update the value.
// Metadata applies metadata to the tag. It is optional.
// Metadatas are applied in the order in which it is provided.
// If more than one metadata updates the same attribute then
// the update from the last metadata prevails.
func Insert(k Key, v string, mds ...Metadata) Mutator {
return &mutator{
fn: func(m *Map) (*Map, error) {
if !checkValue(v) {
return nil, errInvalidValue
}
m.insert(k, v, createMetadatas(mds...))
return m, nil
},
}
}
// Update returns a mutator that updates the
// value of the tag associated with k with v. If k doesn't
// exists in the tag map, the mutator doesn't insert the value.
// Metadata applies metadata to the tag. It is optional.
// Metadatas are applied in the order in which it is provided.
// If more than one metadata updates the same attribute then
// the update from the last metadata prevails.
func Update(k Key, v string, mds ...Metadata) Mutator {
return &mutator{
fn: func(m *Map) (*Map, error) {
if !checkValue(v) {
return nil, errInvalidValue
}
m.update(k, v, createMetadatas(mds...))
return m, nil
},
}
}
// Upsert returns a mutator that upserts the
// value of the tag associated with k with v. It inserts the
// value if k doesn't exist already. It mutates the value
// if k already exists.
// Metadata applies metadata to the tag. It is optional.
// Metadatas are applied in the order in which it is provided.
// If more than one metadata updates the same attribute then
// the update from the last metadata prevails.
func Upsert(k Key, v string, mds ...Metadata) Mutator {
return &mutator{
fn: func(m *Map) (*Map, error) {
if !checkValue(v) {
return nil, errInvalidValue
}
m.upsert(k, v, createMetadatas(mds...))
return m, nil
},
}
}
func createMetadatas(mds ...Metadata) metadatas {
var metas metadatas
if len(mds) > 0 {
for _, md := range mds {
if md != nil {
md(&metas)
}
}
} else {
WithTTL(TTLUnlimitedPropagation)(&metas)
}
return metas
}
// Delete returns a mutator that deletes
// the value associated with k.
func Delete(k Key) Mutator {
return &mutator{
fn: func(m *Map) (*Map, error) {
m.delete(k)
return m, nil
},
}
}
// New returns a new context that contains a tag map
// originated from the incoming context and modified
// with the provided mutators.
func New(ctx context.Context, mutator ...Mutator) (context.Context, error) {
m := newMap()
orig := FromContext(ctx)
if orig != nil {
for k, v := range orig.m {
if !checkKeyName(k.Name()) {
return ctx, fmt.Errorf("key:%q: %v", k, errInvalidKeyName)
}
if !checkValue(v.value) {
return ctx, fmt.Errorf("key:%q value:%q: %v", k.Name(), v, errInvalidValue)
}
m.insert(k, v.value, v.m)
}
}
var err error
for _, mod := range mutator {
m, err = mod.Mutate(m)
if err != nil {
return ctx, err
}
}
return NewContext(ctx, m), nil
}
// Do is similar to pprof.Do: a convenience for installing the tags
// from the context as Go profiler labels. This allows you to
// correlated runtime profiling with stats.
//
// It converts the key/values from the given map to Go profiler labels
// and calls pprof.Do.
//
// Do is going to do nothing if your Go version is below 1.9.
func Do(ctx context.Context, f func(ctx context.Context)) {
do(ctx, f)
}
type mutator struct {
fn func(t *Map) (*Map, error)
}
func (m *mutator) Mutate(t *Map) (*Map, error) {
return m.fn(t)
}