148 lines
4.6 KiB
Go
148 lines
4.6 KiB
Go
// Copyright 2018, OpenCensus Authors
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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// Package tracestate implements support for the Tracestate header of the
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// W3C TraceContext propagation format.
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package tracestate
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import (
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"fmt"
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"regexp"
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)
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const (
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keyMaxSize = 256
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valueMaxSize = 256
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maxKeyValuePairs = 32
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)
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const (
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keyWithoutVendorFormat = `[a-z][_0-9a-z\-\*\/]{0,255}`
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keyWithVendorFormat = `[a-z][_0-9a-z\-\*\/]{0,240}@[a-z][_0-9a-z\-\*\/]{0,13}`
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keyFormat = `(` + keyWithoutVendorFormat + `)|(` + keyWithVendorFormat + `)`
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valueFormat = `[\x20-\x2b\x2d-\x3c\x3e-\x7e]{0,255}[\x21-\x2b\x2d-\x3c\x3e-\x7e]`
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)
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var keyValidationRegExp = regexp.MustCompile(`^(` + keyFormat + `)$`)
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var valueValidationRegExp = regexp.MustCompile(`^(` + valueFormat + `)$`)
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// Tracestate represents tracing-system specific context in a list of key-value pairs. Tracestate allows different
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// vendors propagate additional information and inter-operate with their legacy Id formats.
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type Tracestate struct {
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entries []Entry
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}
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// Entry represents one key-value pair in a list of key-value pair of Tracestate.
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type Entry struct {
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// Key is an opaque string up to 256 characters printable. It MUST begin with a lowercase letter,
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// and can only contain lowercase letters a-z, digits 0-9, underscores _, dashes -, asterisks *, and
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// forward slashes /.
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Key string
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// Value is an opaque string up to 256 characters printable ASCII RFC0020 characters (i.e., the
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// range 0x20 to 0x7E) except comma , and =.
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Value string
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}
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// Entries returns a slice of Entry.
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func (ts *Tracestate) Entries() []Entry {
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if ts == nil {
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return nil
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}
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return ts.entries
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}
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func (ts *Tracestate) remove(key string) *Entry {
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for index, entry := range ts.entries {
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if entry.Key == key {
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ts.entries = append(ts.entries[:index], ts.entries[index+1:]...)
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return &entry
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}
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}
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return nil
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}
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func (ts *Tracestate) add(entries []Entry) error {
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for _, entry := range entries {
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ts.remove(entry.Key)
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}
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if len(ts.entries)+len(entries) > maxKeyValuePairs {
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return fmt.Errorf("adding %d key-value pairs to current %d pairs exceeds the limit of %d",
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len(entries), len(ts.entries), maxKeyValuePairs)
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}
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ts.entries = append(entries, ts.entries...)
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return nil
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}
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func isValid(entry Entry) bool {
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return keyValidationRegExp.MatchString(entry.Key) &&
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valueValidationRegExp.MatchString(entry.Value)
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}
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func containsDuplicateKey(entries ...Entry) (string, bool) {
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keyMap := make(map[string]int)
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for _, entry := range entries {
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if _, ok := keyMap[entry.Key]; ok {
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return entry.Key, true
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}
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keyMap[entry.Key] = 1
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}
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return "", false
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}
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func areEntriesValid(entries ...Entry) (*Entry, bool) {
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for _, entry := range entries {
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if !isValid(entry) {
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return &entry, false
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}
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}
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return nil, true
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}
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// New creates a Tracestate object from a parent and/or entries (key-value pair).
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// Entries from the parent are copied if present. The entries passed to this function
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// are inserted in front of those copied from the parent. If an entry copied from the
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// parent contains the same key as one of the entry in entries then the entry copied
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// from the parent is removed. See add func.
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//
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// An error is returned with nil Tracestate if
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// 1. one or more entry in entries is invalid.
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// 2. two or more entries in the input entries have the same key.
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// 3. the number of entries combined from the parent and the input entries exceeds maxKeyValuePairs.
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// (duplicate entry is counted only once).
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func New(parent *Tracestate, entries ...Entry) (*Tracestate, error) {
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if parent == nil && len(entries) == 0 {
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return nil, nil
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}
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if entry, ok := areEntriesValid(entries...); !ok {
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return nil, fmt.Errorf("key-value pair {%s, %s} is invalid", entry.Key, entry.Value)
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}
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if key, duplicate := containsDuplicateKey(entries...); duplicate {
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return nil, fmt.Errorf("contains duplicate keys (%s)", key)
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}
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tracestate := Tracestate{}
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if parent != nil && len(parent.entries) > 0 {
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tracestate.entries = append([]Entry{}, parent.entries...)
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}
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err := tracestate.add(entries)
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if err != nil {
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return nil, err
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}
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return &tracestate, nil
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}
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