blob: 1831bc9b263716538d11349b849f0fc628cb21a2 [file] [log] [blame]
Girish Kumare48ec8a2020-08-18 12:28:51 +00001package opentracing
2
3import "context"
4
5type contextKey struct{}
6
7var activeSpanKey = contextKey{}
8
9// ContextWithSpan returns a new `context.Context` that holds a reference to
David K. Bainbridgebd6b2882021-08-26 13:31:02 +000010// the span. If span is nil, a new context without an active span is returned.
Girish Kumare48ec8a2020-08-18 12:28:51 +000011func ContextWithSpan(ctx context.Context, span Span) context.Context {
David K. Bainbridgebd6b2882021-08-26 13:31:02 +000012 if span != nil {
13 if tracerWithHook, ok := span.Tracer().(TracerContextWithSpanExtension); ok {
14 ctx = tracerWithHook.ContextWithSpanHook(ctx, span)
15 }
16 }
Girish Kumare48ec8a2020-08-18 12:28:51 +000017 return context.WithValue(ctx, activeSpanKey, span)
18}
19
20// SpanFromContext returns the `Span` previously associated with `ctx`, or
21// `nil` if no such `Span` could be found.
22//
23// NOTE: context.Context != SpanContext: the former is Go's intra-process
24// context propagation mechanism, and the latter houses OpenTracing's per-Span
25// identity and baggage information.
26func SpanFromContext(ctx context.Context) Span {
27 val := ctx.Value(activeSpanKey)
28 if sp, ok := val.(Span); ok {
29 return sp
30 }
31 return nil
32}
33
34// StartSpanFromContext starts and returns a Span with `operationName`, using
35// any Span found within `ctx` as a ChildOfRef. If no such parent could be
36// found, StartSpanFromContext creates a root (parentless) Span.
37//
38// The second return value is a context.Context object built around the
39// returned Span.
40//
41// Example usage:
42//
43// SomeFunction(ctx context.Context, ...) {
44// sp, ctx := opentracing.StartSpanFromContext(ctx, "SomeFunction")
45// defer sp.Finish()
46// ...
47// }
48func StartSpanFromContext(ctx context.Context, operationName string, opts ...StartSpanOption) (Span, context.Context) {
49 return StartSpanFromContextWithTracer(ctx, GlobalTracer(), operationName, opts...)
50}
51
52// StartSpanFromContextWithTracer starts and returns a span with `operationName`
53// using a span found within the context as a ChildOfRef. If that doesn't exist
54// it creates a root span. It also returns a context.Context object built
55// around the returned span.
56//
57// It's behavior is identical to StartSpanFromContext except that it takes an explicit
58// tracer as opposed to using the global tracer.
59func StartSpanFromContextWithTracer(ctx context.Context, tracer Tracer, operationName string, opts ...StartSpanOption) (Span, context.Context) {
60 if parentSpan := SpanFromContext(ctx); parentSpan != nil {
61 opts = append(opts, ChildOf(parentSpan.Context()))
62 }
63 span := tracer.StartSpan(operationName, opts...)
64 return span, ContextWithSpan(ctx, span)
65}