Dynamic Configuration Refactoring

old/middlewares/tracing/forwarder.go

@@ -0,0 +1,63 @@
+package tracing
+
+import (
+	"fmt"
+	"net/http"
+
+	"github.com/containous/traefik/old/log"
+	"github.com/opentracing/opentracing-go/ext"
+	"github.com/urfave/negroni"
+)
+
+type forwarderMiddleware struct {
+	frontend string
+	backend  string
+	opName   string
+	*Tracing
+}
+
+// NewForwarderMiddleware creates a new forwarder middleware that traces the outgoing request
+func (t *Tracing) NewForwarderMiddleware(frontend, backend string) negroni.Handler {
+	log.Debugf("Added outgoing tracing middleware %s", frontend)
+	return &forwarderMiddleware{
+		Tracing:  t,
+		frontend: frontend,
+		backend:  backend,
+		opName:   generateForwardSpanName(frontend, backend, t.SpanNameLimit),
+	}
+}
+
+func (f *forwarderMiddleware) ServeHTTP(w http.ResponseWriter, r *http.Request, next http.HandlerFunc) {
+	span, r, finish := StartSpan(r, f.opName, true)
+	defer finish()
+	span.SetTag("frontend.name", f.frontend)
+	span.SetTag("backend.name", f.backend)
+	ext.HTTPMethod.Set(span, r.Method)
+	ext.HTTPUrl.Set(span, fmt.Sprintf("%s%s", r.URL.String(), r.RequestURI))
+	span.SetTag("http.host", r.Host)
+
+	InjectRequestHeaders(r)
+
+	recorder := newStatusCodeRecoder(w, 200)
+
+	next(recorder, r)
+
+	LogResponseCode(span, recorder.Status())
+}
+
+// generateForwardSpanName will return a Span name of an appropriate lenth based on the 'spanLimit' argument.  If needed, it will be truncated, but will not be less than 21 characters
+func generateForwardSpanName(frontend, backend string, spanLimit int) string {
+	name := fmt.Sprintf("forward %s/%s", frontend, backend)
+
+	if spanLimit > 0 && len(name) > spanLimit {
+		if spanLimit < ForwardMaxLengthNumber {
+			log.Warnf("SpanNameLimit is set to be less than required static number of characters, defaulting to %d + 3", ForwardMaxLengthNumber)
+			spanLimit = ForwardMaxLengthNumber + 3
+		}
+		hash := computeHash(name)
+		limit := (spanLimit - ForwardMaxLengthNumber) / 2
+		name = fmt.Sprintf("forward %s/%s/%s", truncateString(frontend, limit), truncateString(backend, limit), hash)
+	}
+
+	return name
+}