Opentracing support

vendor/github.com/openzipkin/zipkin-go-opentracing/observer.go

@@ -0,0 +1,52 @@
+package zipkintracer
+
+import (
+	opentracing "github.com/opentracing/opentracing-go"
+	otobserver "github.com/opentracing-contrib/go-observer"
+)
+
+// observer is a dispatcher to other observers
+type observer struct {
+	observers []otobserver.Observer
+}
+
+// spanObserver is a dispatcher to other span observers
+type spanObserver struct {
+	observers []otobserver.SpanObserver
+}
+
+func (o observer) OnStartSpan(sp opentracing.Span, operationName string, options opentracing.StartSpanOptions) (otobserver.SpanObserver, bool) {
+	var spanObservers []otobserver.SpanObserver
+	for _, obs := range o.observers {
+		spanObs, ok := obs.OnStartSpan(sp, operationName, options)
+		if ok {
+			if spanObservers == nil {
+				spanObservers = make([]otobserver.SpanObserver, 0, len(o.observers))
+			}
+			spanObservers = append(spanObservers, spanObs)
+		}
+	}
+	if len(spanObservers) == 0 {
+		return nil, false
+	}
+
+	return spanObserver{observers: spanObservers}, true
+}
+
+func (o spanObserver) OnSetOperationName(operationName string) {
+	for _, obs := range o.observers {
+		obs.OnSetOperationName(operationName)
+	}
+}
+
+func (o spanObserver) OnSetTag(key string, value interface{}) {
+	for _, obs := range o.observers {
+		obs.OnSetTag(key, value)
+	}
+}
+
+func (o spanObserver) OnFinish(options opentracing.FinishOptions) {
+	for _, obs := range o.observers {
+		obs.OnFinish(options)
+	}
+}