tracestate.go raw
1 // Copyright The OpenTelemetry Authors
2 // SPDX-License-Identifier: Apache-2.0
3
4 package trace // import "go.opentelemetry.io/otel/trace"
5
6 import (
7 "encoding/json"
8 "fmt"
9 "strings"
10 )
11
12 const (
13 maxListMembers = 32
14
15 listDelimiters = ","
16 memberDelimiter = "="
17
18 errInvalidKey errorConst = "invalid tracestate key"
19 errInvalidValue errorConst = "invalid tracestate value"
20 errInvalidMember errorConst = "invalid tracestate list-member"
21 errMemberNumber errorConst = "too many list-members in tracestate"
22 errDuplicate errorConst = "duplicate list-member in tracestate"
23 )
24
25 type member struct {
26 Key string
27 Value string
28 }
29
30 // according to (chr = %x20 / (nblk-char = %x21-2B / %x2D-3C / %x3E-7E) )
31 // means (chr = %x20-2B / %x2D-3C / %x3E-7E) .
32 func checkValueChar(v byte) bool {
33 return v >= '\x20' && v <= '\x7e' && v != '\x2c' && v != '\x3d'
34 }
35
36 // according to (nblk-chr = %x21-2B / %x2D-3C / %x3E-7E) .
37 func checkValueLast(v byte) bool {
38 return v >= '\x21' && v <= '\x7e' && v != '\x2c' && v != '\x3d'
39 }
40
41 // based on the W3C Trace Context specification
42 //
43 // value = (0*255(chr)) nblk-chr
44 // nblk-chr = %x21-2B / %x2D-3C / %x3E-7E
45 // chr = %x20 / nblk-chr
46 //
47 // see https://www.w3.org/TR/trace-context-1/#value
48 func checkValue(val string) bool {
49 n := len(val)
50 if n == 0 || n > 256 {
51 return false
52 }
53 for i := 0; i < n-1; i++ {
54 if !checkValueChar(val[i]) {
55 return false
56 }
57 }
58 return checkValueLast(val[n-1])
59 }
60
61 func checkKeyRemain(key string) bool {
62 // ( lcalpha / DIGIT / "_" / "-"/ "*" / "/" )
63 for _, v := range key {
64 if isAlphaNum(byte(v)) {
65 continue
66 }
67 switch v {
68 case '_', '-', '*', '/':
69 continue
70 }
71 return false
72 }
73 return true
74 }
75
76 // according to
77 //
78 // simple-key = lcalpha (0*255( lcalpha / DIGIT / "_" / "-"/ "*" / "/" ))
79 // system-id = lcalpha (0*13( lcalpha / DIGIT / "_" / "-"/ "*" / "/" ))
80 //
81 // param n is remain part length, should be 255 in simple-key or 13 in system-id.
82 func checkKeyPart(key string, n int) bool {
83 if key == "" {
84 return false
85 }
86 first := key[0] // key's first char
87 ret := len(key[1:]) <= n
88 ret = ret && first >= 'a' && first <= 'z'
89 return ret && checkKeyRemain(key[1:])
90 }
91
92 func isAlphaNum(c byte) bool {
93 if c >= 'a' && c <= 'z' {
94 return true
95 }
96 return c >= '0' && c <= '9'
97 }
98
99 // according to
100 //
101 // tenant-id = ( lcalpha / DIGIT ) 0*240( lcalpha / DIGIT / "_" / "-"/ "*" / "/" )
102 //
103 // param n is remain part length, should be 240 exactly.
104 func checkKeyTenant(key string, n int) bool {
105 if key == "" {
106 return false
107 }
108 return isAlphaNum(key[0]) && len(key[1:]) <= n && checkKeyRemain(key[1:])
109 }
110
111 // based on the W3C Trace Context specification
112 //
113 // key = simple-key / multi-tenant-key
114 // simple-key = lcalpha (0*255( lcalpha / DIGIT / "_" / "-"/ "*" / "/" ))
115 // multi-tenant-key = tenant-id "@" system-id
116 // tenant-id = ( lcalpha / DIGIT ) (0*240( lcalpha / DIGIT / "_" / "-"/ "*" / "/" ))
117 // system-id = lcalpha (0*13( lcalpha / DIGIT / "_" / "-"/ "*" / "/" ))
118 // lcalpha = %x61-7A ; a-z
119 //
120 // see https://www.w3.org/TR/trace-context-1/#tracestate-header.
121 func checkKey(key string) bool {
122 tenant, system, ok := strings.Cut(key, "@")
123 if !ok {
124 return checkKeyPart(key, 255)
125 }
126 return checkKeyTenant(tenant, 240) && checkKeyPart(system, 13)
127 }
128
129 func newMember(key, value string) (member, error) {
130 if !checkKey(key) {
131 return member{}, errInvalidKey
132 }
133 if !checkValue(value) {
134 return member{}, errInvalidValue
135 }
136 return member{Key: key, Value: value}, nil
137 }
138
139 func parseMember(m string) (member, error) {
140 key, val, ok := strings.Cut(m, memberDelimiter)
141 if !ok {
142 return member{}, fmt.Errorf("%w: %s", errInvalidMember, m)
143 }
144 key = strings.TrimLeft(key, " \t")
145 val = strings.TrimRight(val, " \t")
146 result, e := newMember(key, val)
147 if e != nil {
148 return member{}, fmt.Errorf("%w: %s", errInvalidMember, m)
149 }
150 return result, nil
151 }
152
153 // String encodes member into a string compliant with the W3C Trace Context
154 // specification.
155 func (m member) String() string {
156 return m.Key + "=" + m.Value
157 }
158
159 // TraceState provides additional vendor-specific trace identification
160 // information across different distributed tracing systems. It represents an
161 // immutable list consisting of key/value pairs, each pair is referred to as a
162 // list-member.
163 //
164 // TraceState conforms to the W3C Trace Context specification
165 // (https://www.w3.org/TR/trace-context-1). All operations that create or copy
166 // a TraceState do so by validating all input and will only produce TraceState
167 // that conform to the specification. Specifically, this means that all
168 // list-member's key/value pairs are valid, no duplicate list-members exist,
169 // and the maximum number of list-members (32) is not exceeded.
170 type TraceState struct { //nolint:revive // revive complains about stutter of `trace.TraceState`
171 // list is the members in order.
172 list []member
173 }
174
175 var _ json.Marshaler = TraceState{}
176
177 // ParseTraceState attempts to decode a TraceState from the passed
178 // string. It returns an error if the input is invalid according to the W3C
179 // Trace Context specification.
180 func ParseTraceState(ts string) (TraceState, error) {
181 if ts == "" {
182 return TraceState{}, nil
183 }
184
185 wrapErr := func(err error) error {
186 return fmt.Errorf("failed to parse tracestate: %w", err)
187 }
188
189 var members []member
190 found := make(map[string]struct{})
191 for ts != "" {
192 var memberStr string
193 memberStr, ts, _ = strings.Cut(ts, listDelimiters)
194 if memberStr == "" {
195 continue
196 }
197
198 m, err := parseMember(memberStr)
199 if err != nil {
200 return TraceState{}, wrapErr(err)
201 }
202
203 if _, ok := found[m.Key]; ok {
204 return TraceState{}, wrapErr(errDuplicate)
205 }
206 found[m.Key] = struct{}{}
207
208 members = append(members, m)
209 if n := len(members); n > maxListMembers {
210 return TraceState{}, wrapErr(errMemberNumber)
211 }
212 }
213
214 return TraceState{list: members}, nil
215 }
216
217 // MarshalJSON marshals the TraceState into JSON.
218 func (ts TraceState) MarshalJSON() ([]byte, error) {
219 return json.Marshal(ts.String())
220 }
221
222 // String encodes the TraceState into a string compliant with the W3C
223 // Trace Context specification. The returned string will be invalid if the
224 // TraceState contains any invalid members.
225 func (ts TraceState) String() string {
226 if len(ts.list) == 0 {
227 return ""
228 }
229 var n int
230 n += len(ts.list) // member delimiters: '='
231 n += len(ts.list) - 1 // list delimiters: ','
232 for _, mem := range ts.list {
233 n += len(mem.Key)
234 n += len(mem.Value)
235 }
236
237 var sb strings.Builder
238 sb.Grow(n)
239 _, _ = sb.WriteString(ts.list[0].Key)
240 _ = sb.WriteByte('=')
241 _, _ = sb.WriteString(ts.list[0].Value)
242 for i := 1; i < len(ts.list); i++ {
243 _ = sb.WriteByte(listDelimiters[0])
244 _, _ = sb.WriteString(ts.list[i].Key)
245 _ = sb.WriteByte('=')
246 _, _ = sb.WriteString(ts.list[i].Value)
247 }
248 return sb.String()
249 }
250
251 // Get returns the value paired with key from the corresponding TraceState
252 // list-member if it exists, otherwise an empty string is returned.
253 func (ts TraceState) Get(key string) string {
254 for _, member := range ts.list {
255 if member.Key == key {
256 return member.Value
257 }
258 }
259
260 return ""
261 }
262
263 // Walk walks all key value pairs in the TraceState by calling f
264 // Iteration stops if f returns false.
265 func (ts TraceState) Walk(f func(key, value string) bool) {
266 for _, m := range ts.list {
267 if !f(m.Key, m.Value) {
268 break
269 }
270 }
271 }
272
273 // Insert adds a new list-member defined by the key/value pair to the
274 // TraceState. If a list-member already exists for the given key, that
275 // list-member's value is updated. The new or updated list-member is always
276 // moved to the beginning of the TraceState as specified by the W3C Trace
277 // Context specification.
278 //
279 // If key or value are invalid according to the W3C Trace Context
280 // specification an error is returned with the original TraceState.
281 //
282 // If adding a new list-member means the TraceState would have more members
283 // then is allowed, the new list-member will be inserted and the right-most
284 // list-member will be dropped in the returned TraceState.
285 func (ts TraceState) Insert(key, value string) (TraceState, error) {
286 m, err := newMember(key, value)
287 if err != nil {
288 return ts, err
289 }
290 n := len(ts.list)
291 found := n
292 for i := range ts.list {
293 if ts.list[i].Key == key {
294 found = i
295 }
296 }
297 cTS := TraceState{}
298 if found == n && n < maxListMembers {
299 cTS.list = make([]member, n+1)
300 } else {
301 cTS.list = make([]member, n)
302 }
303 cTS.list[0] = m
304 // When the number of members exceeds capacity, drop the "right-most".
305 copy(cTS.list[1:], ts.list[0:found])
306 if found < n {
307 copy(cTS.list[1+found:], ts.list[found+1:])
308 }
309 return cTS, nil
310 }
311
312 // Delete returns a copy of the TraceState with the list-member identified by
313 // key removed.
314 func (ts TraceState) Delete(key string) TraceState {
315 members := make([]member, ts.Len())
316 copy(members, ts.list)
317 for i, member := range ts.list {
318 if member.Key == key {
319 members = append(members[:i], members[i+1:]...)
320 // TraceState should contain no duplicate members.
321 break
322 }
323 }
324 return TraceState{list: members}
325 }
326
327 // Len returns the number of list-members in the TraceState.
328 func (ts TraceState) Len() int {
329 return len(ts.list)
330 }
331