cloudflared-mirror/vendor/go.opentelemetry.io/otel/trace/tracestate.go

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2022-04-06 23:20:29 +00:00
// Copyright The OpenTelemetry 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 trace // import "go.opentelemetry.io/otel/trace"
import (
"encoding/json"
"fmt"
"regexp"
"strings"
)
var (
maxListMembers = 32
listDelimiter = ","
// based on the W3C Trace Context specification, see
// https://www.w3.org/TR/trace-context-1/#tracestate-header
noTenantKeyFormat = `[a-z][_0-9a-z\-\*\/]{0,255}`
withTenantKeyFormat = `[a-z0-9][_0-9a-z\-\*\/]{0,240}@[a-z][_0-9a-z\-\*\/]{0,13}`
valueFormat = `[\x20-\x2b\x2d-\x3c\x3e-\x7e]{0,255}[\x21-\x2b\x2d-\x3c\x3e-\x7e]`
keyRe = regexp.MustCompile(`^((` + noTenantKeyFormat + `)|(` + withTenantKeyFormat + `))$`)
valueRe = regexp.MustCompile(`^(` + valueFormat + `)$`)
memberRe = regexp.MustCompile(`^\s*((` + noTenantKeyFormat + `)|(` + withTenantKeyFormat + `))=(` + valueFormat + `)\s*$`)
errInvalidKey errorConst = "invalid tracestate key"
errInvalidValue errorConst = "invalid tracestate value"
errInvalidMember errorConst = "invalid tracestate list-member"
errMemberNumber errorConst = "too many list-members in tracestate"
errDuplicate errorConst = "duplicate list-member in tracestate"
)
type member struct {
Key string
Value string
}
func newMember(key, value string) (member, error) {
if !keyRe.MatchString(key) {
return member{}, fmt.Errorf("%w: %s", errInvalidKey, key)
}
if !valueRe.MatchString(value) {
return member{}, fmt.Errorf("%w: %s", errInvalidValue, value)
}
return member{Key: key, Value: value}, nil
}
func parseMember(m string) (member, error) {
matches := memberRe.FindStringSubmatch(m)
if len(matches) != 5 {
return member{}, fmt.Errorf("%w: %s", errInvalidMember, m)
}
return member{
Key: matches[1],
Value: matches[4],
}, nil
}
// String encodes member into a string compliant with the W3C Trace Context
// specification.
func (m member) String() string {
return fmt.Sprintf("%s=%s", m.Key, m.Value)
}
// TraceState provides additional vendor-specific trace identification
// information across different distributed tracing systems. It represents an
// immutable list consisting of key/value pairs, each pair is referred to as a
// list-member.
//
// TraceState conforms to the W3C Trace Context specification
// (https://www.w3.org/TR/trace-context-1). All operations that create or copy
// a TraceState do so by validating all input and will only produce TraceState
// that conform to the specification. Specifically, this means that all
// list-member's key/value pairs are valid, no duplicate list-members exist,
// and the maximum number of list-members (32) is not exceeded.
type TraceState struct { //nolint:revive // revive complains about stutter of `trace.TraceState`
// list is the members in order.
list []member
}
var _ json.Marshaler = TraceState{}
// ParseTraceState attempts to decode a TraceState from the passed
// string. It returns an error if the input is invalid according to the W3C
// Trace Context specification.
func ParseTraceState(tracestate string) (TraceState, error) {
if tracestate == "" {
return TraceState{}, nil
}
wrapErr := func(err error) error {
return fmt.Errorf("failed to parse tracestate: %w", err)
}
var members []member
found := make(map[string]struct{})
for _, memberStr := range strings.Split(tracestate, listDelimiter) {
if len(memberStr) == 0 {
continue
}
m, err := parseMember(memberStr)
if err != nil {
return TraceState{}, wrapErr(err)
}
if _, ok := found[m.Key]; ok {
return TraceState{}, wrapErr(errDuplicate)
}
found[m.Key] = struct{}{}
members = append(members, m)
if n := len(members); n > maxListMembers {
return TraceState{}, wrapErr(errMemberNumber)
}
}
return TraceState{list: members}, nil
}
// MarshalJSON marshals the TraceState into JSON.
func (ts TraceState) MarshalJSON() ([]byte, error) {
return json.Marshal(ts.String())
}
// String encodes the TraceState into a string compliant with the W3C
// Trace Context specification. The returned string will be invalid if the
// TraceState contains any invalid members.
func (ts TraceState) String() string {
members := make([]string, len(ts.list))
for i, m := range ts.list {
members[i] = m.String()
}
return strings.Join(members, listDelimiter)
}
// Get returns the value paired with key from the corresponding TraceState
// list-member if it exists, otherwise an empty string is returned.
func (ts TraceState) Get(key string) string {
for _, member := range ts.list {
if member.Key == key {
return member.Value
}
}
return ""
}
// Insert adds a new list-member defined by the key/value pair to the
// TraceState. If a list-member already exists for the given key, that
// list-member's value is updated. The new or updated list-member is always
// moved to the beginning of the TraceState as specified by the W3C Trace
// Context specification.
//
// If key or value are invalid according to the W3C Trace Context
// specification an error is returned with the original TraceState.
//
// If adding a new list-member means the TraceState would have more members
// then is allowed, the new list-member will be inserted and the right-most
// list-member will be dropped in the returned TraceState.
func (ts TraceState) Insert(key, value string) (TraceState, error) {
m, err := newMember(key, value)
if err != nil {
return ts, err
}
cTS := ts.Delete(key)
if cTS.Len()+1 <= maxListMembers {
cTS.list = append(cTS.list, member{})
}
// When the number of members exceeds capacity, drop the "right-most".
copy(cTS.list[1:], cTS.list)
cTS.list[0] = m
return cTS, nil
}
// Delete returns a copy of the TraceState with the list-member identified by
// key removed.
func (ts TraceState) Delete(key string) TraceState {
members := make([]member, ts.Len())
copy(members, ts.list)
for i, member := range ts.list {
if member.Key == key {
members = append(members[:i], members[i+1:]...)
// TraceState should contain no duplicate members.
break
}
}
return TraceState{list: members}
}
// Len returns the number of list-members in the TraceState.
func (ts TraceState) Len() int {
return len(ts.list)
}