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- package opentracing
- import "context"
- type contextKey struct{}
- var activeSpanKey = contextKey{}
- // ContextWithSpan returns a new `context.Context` that holds a reference to
- // the span. If span is nil, a new context without an active span is returned.
- func ContextWithSpan(ctx context.Context, span Span) context.Context {
- if span != nil {
- if tracerWithHook, ok := span.Tracer().(TracerContextWithSpanExtension); ok {
- ctx = tracerWithHook.ContextWithSpanHook(ctx, span)
- }
- }
- return context.WithValue(ctx, activeSpanKey, span)
- }
- // SpanFromContext returns the `Span` previously associated with `ctx`, or
- // `nil` if no such `Span` could be found.
- //
- // NOTE: context.Context != SpanContext: the former is Go's intra-process
- // context propagation mechanism, and the latter houses OpenTracing's per-Span
- // identity and baggage information.
- func SpanFromContext(ctx context.Context) Span {
- val := ctx.Value(activeSpanKey)
- if sp, ok := val.(Span); ok {
- return sp
- }
- return nil
- }
- // StartSpanFromContext starts and returns a Span with `operationName`, using
- // any Span found within `ctx` as a ChildOfRef. If no such parent could be
- // found, StartSpanFromContext creates a root (parentless) Span.
- //
- // The second return value is a context.Context object built around the
- // returned Span.
- //
- // Example usage:
- //
- // SomeFunction(ctx context.Context, ...) {
- // sp, ctx := opentracing.StartSpanFromContext(ctx, "SomeFunction")
- // defer sp.Finish()
- // ...
- // }
- func StartSpanFromContext(ctx context.Context, operationName string, opts ...StartSpanOption) (Span, context.Context) {
- return StartSpanFromContextWithTracer(ctx, GlobalTracer(), operationName, opts...)
- }
- // StartSpanFromContextWithTracer starts and returns a span with `operationName`
- // using a span found within the context as a ChildOfRef. If that doesn't exist
- // it creates a root span. It also returns a context.Context object built
- // around the returned span.
- //
- // It's behavior is identical to StartSpanFromContext except that it takes an explicit
- // tracer as opposed to using the global tracer.
- func StartSpanFromContextWithTracer(ctx context.Context, tracer Tracer, operationName string, opts ...StartSpanOption) (Span, context.Context) {
- if parentSpan := SpanFromContext(ctx); parentSpan != nil {
- opts = append(opts, ChildOf(parentSpan.Context()))
- }
- span := tracer.StartSpan(operationName, opts...)
- return span, ContextWithSpan(ctx, span)
- }
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