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// Copyright 2021 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package otel
import (
"context"
"go.opentelemetry.io/otel/trace"
"golang.org/x/exp/event"
)
type TraceHandler struct {
tracer trace.Tracer
}
func NewTraceHandler(t trace.Tracer) *TraceHandler {
return &TraceHandler{tracer: t}
}
type spanKey struct{}
func (t *TraceHandler) Event(ctx context.Context, ev *event.Event) context.Context {
switch ev.Kind {
case event.StartKind:
name, opts := labelsToSpanStartOptions(ev.Labels)
octx, span := t.tracer.Start(ctx, name, opts...)
return context.WithValue(octx, spanKey{}, span)
case event.EndKind:
span, ok := ctx.Value(spanKey{}).(trace.Span)
if !ok {
panic("End called on context with no span")
}
span.End()
return ctx
default:
return ctx
}
}
func labelsToSpanStartOptions(ls []event.Label) (string, []trace.SpanStartOption) {
var opts []trace.SpanStartOption
var name string
for _, l := range ls {
switch l.Name {
case "link":
opts = append(opts, trace.WithLinks(l.Interface().(trace.Link)))
case "newRoot":
opts = append(opts, trace.WithNewRoot())
case "spanKind":
opts = append(opts, trace.WithSpanKind(l.Interface().(trace.SpanKind)))
case "name":
name = l.String()
}
}
return name, opts
}
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