1 // Copyright The OpenTelemetry Authors
2 // SPDX-License-Identifier: Apache-2.0
3 4 package otelhttp // import "go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp"
5 6 import (
7 "context"
8 "sync"
9 10 "go.opentelemetry.io/otel/attribute"
11 )
12 13 // Labeler is used to allow instrumented HTTP handlers to add custom attributes to
14 // the metrics recorded by the net/http instrumentation.
15 type Labeler struct {
16 mu sync.Mutex
17 attributes []attribute.KeyValue
18 }
19 20 // Add attributes to a Labeler.
21 func (l *Labeler) Add(ls ...attribute.KeyValue) {
22 l.mu.Lock()
23 defer l.mu.Unlock()
24 l.attributes = append(l.attributes, ls...)
25 }
26 27 // Get returns a copy of the attributes added to the Labeler.
28 func (l *Labeler) Get() []attribute.KeyValue {
29 l.mu.Lock()
30 defer l.mu.Unlock()
31 ret := make([]attribute.KeyValue, len(l.attributes))
32 copy(ret, l.attributes)
33 return ret
34 }
35 36 type labelerContextKeyType int
37 38 const labelerContextKey labelerContextKeyType = 0
39 40 // ContextWithLabeler returns a new context with the provided Labeler instance.
41 // Attributes added to the specified labeler will be injected into metrics
42 // emitted by the instrumentation. Only one labeller can be injected into the
43 // context. Injecting it multiple times will override the previous calls.
44 func ContextWithLabeler(parent context.Context, l *Labeler) context.Context {
45 return context.WithValue(parent, labelerContextKey, l)
46 }
47 48 // LabelerFromContext retrieves a Labeler instance from the provided context if
49 // one is available. If no Labeler was found in the provided context a new, empty
50 // Labeler is returned and the second return value is false. In this case it is
51 // safe to use the Labeler but any attributes added to it will not be used.
52 func LabelerFromContext(ctx context.Context) (*Labeler, bool) {
53 l, ok := ctx.Value(labelerContextKey).(*Labeler)
54 if !ok {
55 l = &Labeler{}
56 }
57 return l, ok
58 }
59