Move code to pkg

pkg/middlewares/tracing/wrapper.go

@@ -0,0 +1,68 @@
+package tracing
+
+import (
+	"context"
+	"net/http"
+
+	"github.com/containous/alice"
+	"github.com/containous/traefik/pkg/log"
+	"github.com/containous/traefik/pkg/tracing"
+	"github.com/opentracing/opentracing-go/ext"
+)
+
+// Tracable embeds tracing information.
+type Tracable interface {
+	GetTracingInformation() (name string, spanKind ext.SpanKindEnum)
+}
+
+// Wrap adds tracability to an alice.Constructor.
+func Wrap(ctx context.Context, constructor alice.Constructor) alice.Constructor {
+	return func(next http.Handler) (http.Handler, error) {
+		if constructor == nil {
+			return nil, nil
+		}
+		handler, err := constructor(next)
+		if err != nil {
+			return nil, err
+		}
+
+		if tracableHandler, ok := handler.(Tracable); ok {
+			name, spanKind := tracableHandler.GetTracingInformation()
+			log.FromContext(ctx).WithField(log.MiddlewareName, name).Debug("Adding tracing to middleware")
+			return NewWrapper(handler, name, spanKind), nil
+		}
+		return handler, nil
+	}
+}
+
+// NewWrapper returns a http.Handler struct
+func NewWrapper(next http.Handler, name string, spanKind ext.SpanKindEnum) http.Handler {
+	return &Wrapper{
+		next:     next,
+		name:     name,
+		spanKind: spanKind,
+	}
+}
+
+// Wrapper is used to wrap http handler middleware.
+type Wrapper struct {
+	next     http.Handler
+	name     string
+	spanKind ext.SpanKindEnum
+}
+
+func (w *Wrapper) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
+	_, err := tracing.FromContext(req.Context())
+	if err != nil {
+		w.next.ServeHTTP(rw, req)
+		return
+	}
+
+	var finish func()
+	_, req, finish = tracing.StartSpan(req, w.name, w.spanKind)
+	defer finish()
+
+	if w.next != nil {
+		w.next.ServeHTTP(rw, req)
+	}
+}