Added integration support for DataDog APM Tracing

vendor/gopkg.in/DataDog/dd-trace-go.v1/ddtrace/opentracer/tracer.go

@@ -0,0 +1,81 @@
+// Package opentracer provides a wrapper on top of the Datadog tracer that can be used with Opentracing.
+// It also provides a set of opentracing.StartSpanOption that are specific to Datadog's APM product.
+// To use it, simply call "New".
+//
+// Note that there are currently some small incompatibilities between the Opentracing spec and the Datadog
+// APM product, which we are in the process of addressing on the long term. When using Datadog, the
+// Opentracing operation name is what is called resource in Datadog's terms and the Opentracing "component"
+// tag is Datadog's operation name. Meaning that in order to define (in Opentracing terms) a span that
+// has the operation name "/user/profile" and the component "http.request", one would do:
+//  opentracing.StartSpan("http.request", opentracer.ResourceName("/user/profile"))
+//
+// Some libraries and frameworks are supported out-of-the-box by using our integrations. You can see a list
+// of supported integrations here: https://godoc.org/gopkg.in/DataDog/dd-trace-go.v1/contrib. They are fully
+// compatible with the Opentracing implementation.
+package opentracer
+
+import (
+	"gopkg.in/DataDog/dd-trace-go.v1/ddtrace"
+	"gopkg.in/DataDog/dd-trace-go.v1/ddtrace/internal"
+	"gopkg.in/DataDog/dd-trace-go.v1/ddtrace/tracer"
+
+	opentracing "github.com/opentracing/opentracing-go"
+)
+
+// New creates, instantiates and returns an Opentracing compatible version of the
+// Datadog tracer using the provided set of options.
+func New(opts ...tracer.StartOption) opentracing.Tracer {
+	tracer.Start(opts...)
+	return &opentracer{internal.GetGlobalTracer()}
+}
+
+var _ opentracing.Tracer = (*opentracer)(nil)
+
+// opentracer implements opentracing.Tracer on top of ddtrace.Tracer.
+type opentracer struct{ ddtrace.Tracer }
+
+// StartSpan implements opentracing.Tracer.
+func (t *opentracer) StartSpan(operationName string, options ...opentracing.StartSpanOption) opentracing.Span {
+	var sso opentracing.StartSpanOptions
+	for _, o := range options {
+		o.Apply(&sso)
+	}
+	opts := []ddtrace.StartSpanOption{tracer.StartTime(sso.StartTime)}
+	for _, ref := range sso.References {
+		if v, ok := ref.ReferencedContext.(ddtrace.SpanContext); ok && ref.Type == opentracing.ChildOfRef {
+			opts = append(opts, tracer.ChildOf(v))
+			break // can only have one parent
+		}
+	}
+	for k, v := range sso.Tags {
+		opts = append(opts, tracer.Tag(k, v))
+	}
+	return &span{
+		Span:       t.Tracer.StartSpan(operationName, opts...),
+		opentracer: t,
+	}
+}
+
+// Inject implements opentracing.Tracer.
+func (t *opentracer) Inject(ctx opentracing.SpanContext, format interface{}, carrier interface{}) error {
+	sctx, ok := ctx.(ddtrace.SpanContext)
+	if !ok {
+		return opentracing.ErrUnsupportedFormat
+	}
+	switch format {
+	case opentracing.TextMap, opentracing.HTTPHeaders:
+		return t.Tracer.Inject(sctx, carrier)
+	default:
+		return opentracing.ErrUnsupportedFormat
+	}
+}
+
+// Extract implements opentracing.Tracer.
+func (t *opentracer) Extract(format interface{}, carrier interface{}) (opentracing.SpanContext, error) {
+	switch format {
+	case opentracing.TextMap, opentracing.HTTPHeaders:
+		return t.Tracer.Extract(carrier)
+	default:
+		return nil, opentracing.ErrUnsupportedFormat
+	}
+}