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// Copyright The OpenTelemetry Authors
// SPDX-License-Identifier: Apache-2.0
package otelhttp // import "go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp"
import (
"context"
"sync"
"go.opentelemetry.io/otel/attribute"
)
// Labeler is used to allow instrumented HTTP handlers to add custom attributes to
// the metrics recorded by the net/http instrumentation.
type Labeler struct {
mu sync.Mutex
attributes []attribute.KeyValue
}
// Add attributes to a Labeler.
func (l *Labeler) Add(ls ...attribute.KeyValue) {
l.mu.Lock()
defer l.mu.Unlock()
l.attributes = append(l.attributes, ls...)
}
// Get returns a copy of the attributes added to the Labeler.
func (l *Labeler) Get() []attribute.KeyValue {
l.mu.Lock()
defer l.mu.Unlock()
ret := make([]attribute.KeyValue, len(l.attributes))
copy(ret, l.attributes)
return ret
}
type labelerContextKeyType int
const lablelerContextKey labelerContextKeyType = 0
// ContextWithLabeler returns a new context with the provided Labeler instance.
// Attributes added to the specified labeler will be injected into metrics
// emitted by the instrumentation. Only one labeller can be injected into the
// context. Injecting it multiple times will override the previous calls.
func ContextWithLabeler(parent context.Context, l *Labeler) context.Context {
return context.WithValue(parent, lablelerContextKey, l)
}
// LabelerFromContext retrieves a Labeler instance from the provided context if
// one is available. If no Labeler was found in the provided context a new, empty
// Labeler is returned and the second return value is false. In this case it is
// safe to use the Labeler but any attributes added to it will not be used.
func LabelerFromContext(ctx context.Context) (*Labeler, bool) {
l, ok := ctx.Value(lablelerContextKey).(*Labeler)
if !ok {
l = &Labeler{}
}
return l, ok
}
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