58 lines
2.0 KiB
Go
58 lines
2.0 KiB
Go
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package opentracing
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import "golang.org/x/net/context"
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type contextKey struct{}
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var activeSpanKey = contextKey{}
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// ContextWithSpan returns a new `context.Context` that holds a reference to
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// `span`'s SpanContext.
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func ContextWithSpan(ctx context.Context, span Span) context.Context {
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return context.WithValue(ctx, activeSpanKey, span)
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}
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// SpanFromContext returns the `Span` previously associated with `ctx`, or
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// `nil` if no such `Span` could be found.
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//
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// NOTE: context.Context != SpanContext: the former is Go's intra-process
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// context propagation mechanism, and the latter houses OpenTracing's per-Span
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// identity and baggage information.
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func SpanFromContext(ctx context.Context) Span {
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val := ctx.Value(activeSpanKey)
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if sp, ok := val.(Span); ok {
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return sp
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}
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return nil
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}
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// StartSpanFromContext starts and returns a Span with `operationName`, using
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// any Span found within `ctx` as a ChildOfRef. If no such parent could be
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// found, StartSpanFromContext creates a root (parentless) Span.
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//
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// The second return value is a context.Context object built around the
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// returned Span.
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//
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// Example usage:
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//
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// SomeFunction(ctx context.Context, ...) {
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// sp, ctx := opentracing.StartSpanFromContext(ctx, "SomeFunction")
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// defer sp.Finish()
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// ...
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// }
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func StartSpanFromContext(ctx context.Context, operationName string, opts ...StartSpanOption) (Span, context.Context) {
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return startSpanFromContextWithTracer(ctx, GlobalTracer(), operationName, opts...)
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}
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// startSpanFromContextWithTracer is factored out for testing purposes.
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func startSpanFromContextWithTracer(ctx context.Context, tracer Tracer, operationName string, opts ...StartSpanOption) (Span, context.Context) {
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var span Span
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if parentSpan := SpanFromContext(ctx); parentSpan != nil {
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opts = append(opts, ChildOf(parentSpan.Context()))
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span = tracer.StartSpan(operationName, opts...)
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} else {
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span = tracer.StartSpan(operationName, opts...)
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}
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return span, ContextWithSpan(ctx, span)
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}
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