Opentracing support

vendor/github.com/opentracing-contrib/go-stdlib/nethttp/server.go

@@ -0,0 +1,96 @@
+// +build go1.7
+
+package nethttp
+
+import (
+	"net/http"
+
+	opentracing "github.com/opentracing/opentracing-go"
+	"github.com/opentracing/opentracing-go/ext"
+)
+
+type statusCodeTracker struct {
+	http.ResponseWriter
+	status int
+}
+
+func (w *statusCodeTracker) WriteHeader(status int) {
+	w.status = status
+	w.ResponseWriter.WriteHeader(status)
+}
+
+type mwOptions struct {
+	opNameFunc    func(r *http.Request) string
+	componentName string
+}
+
+// MWOption controls the behavior of the Middleware.
+type MWOption func(*mwOptions)
+
+// OperationNameFunc returns a MWOption that uses given function f
+// to generate operation name for each server-side span.
+func OperationNameFunc(f func(r *http.Request) string) MWOption {
+	return func(options *mwOptions) {
+		options.opNameFunc = f
+	}
+}
+
+// MWComponentName returns a MWOption that sets the component name
+// name for the server-side span.
+func MWComponentName(componentName string) MWOption {
+	return func(options *mwOptions) {
+		options.componentName = componentName
+	}
+}
+
+// Middleware wraps an http.Handler and traces incoming requests.
+// Additionally, it adds the span to the request's context.
+//
+// By default, the operation name of the spans is set to "HTTP {method}".
+// This can be overriden with options.
+//
+// Example:
+// 	 http.ListenAndServe("localhost:80", nethttp.Middleware(tracer, http.DefaultServeMux))
+//
+// The options allow fine tuning the behavior of the middleware.
+//
+// Example:
+//   mw := nethttp.Middleware(
+//      tracer,
+//      http.DefaultServeMux,
+//      nethttp.OperationName(func(r *http.Request) string {
+//	        return "HTTP " + r.Method + ":/api/customers"
+//      }),
+//   )
+func Middleware(tr opentracing.Tracer, h http.Handler, options ...MWOption) http.Handler {
+	opts := mwOptions{
+		opNameFunc: func(r *http.Request) string {
+			return "HTTP " + r.Method
+		},
+	}
+	for _, opt := range options {
+		opt(&opts)
+	}
+	fn := func(w http.ResponseWriter, r *http.Request) {
+		ctx, _ := tr.Extract(opentracing.HTTPHeaders, opentracing.HTTPHeadersCarrier(r.Header))
+		sp := tr.StartSpan(opts.opNameFunc(r), ext.RPCServerOption(ctx))
+		ext.HTTPMethod.Set(sp, r.Method)
+		ext.HTTPUrl.Set(sp, r.URL.String())
+
+		// set component name, use "net/http" if caller does not specify
+		componentName := opts.componentName
+		if componentName == "" {
+			componentName = defaultComponentName
+		}
+		ext.Component.Set(sp, componentName)
+
+		w = &statusCodeTracker{w, 200}
+		r = r.WithContext(opentracing.ContextWithSpan(r.Context(), sp))
+
+		h.ServeHTTP(w, r)
+
+		ext.HTTPStatusCode.Set(sp, uint16(w.(*statusCodeTracker).status))
+		sp.Finish()
+	}
+	return http.HandlerFunc(fn)
+}