micro/tracer/context.go

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// Package tracer provides an interface for distributed tracing
package tracer
import (
"context"
)
type tracerKey struct{}
// FromContext returns a tracer from context
func FromContext(ctx context.Context) (Tracer, bool) {
if ctx == nil {
return nil, false
}
if tracer, ok := ctx.Value(tracerKey{}).(Tracer); ok {
return tracer, true
}
return nil, false
}
// NewContext saves the tracer in the context
func NewContext(ctx context.Context, tracer Tracer) context.Context {
if ctx == nil {
ctx = context.Background()
}
return context.WithValue(ctx, tracerKey{}, tracer)
}
type spanKey struct{}
// SpanFromContext returns a span from context
func SpanFromContext(ctx context.Context) (Span, bool) {
if ctx == nil {
return nil, false
}
if span, ok := ctx.Value(spanKey{}).(Span); ok {
return span, true
}
return nil, false
}
// NewSpanContext saves the span in the context
func NewSpanContext(ctx context.Context, span Span) context.Context {
if ctx == nil {
ctx = context.Background()
}
return context.WithValue(ctx, spanKey{}, span)
}
// SetOption returns a function to setup a context with given value
func SetOption(k, v interface{}) Option {
return func(o *Options) {
if o.Context == nil {
o.Context = context.Background()
}
o.Context = context.WithValue(o.Context, k, v)
}
}