Add util

util/http/roundtripper.go

@@ -0,0 +1,40 @@
+package http
+
+import (
+	"errors"
+	"fmt"
+	"net/http"
+
+	"github.com/micro/go-micro/selector"
+)
+
+type roundTripper struct {
+	rt   http.RoundTripper
+	st   selector.Strategy
+	opts Options
+}
+
+func (r *roundTripper) RoundTrip(req *http.Request) (*http.Response, error) {
+	s, err := r.opts.Registry.GetService(req.URL.Host)
+	if err != nil {
+		return nil, err
+	}
+
+	next := r.st(s)
+
+	// rudimentary retry 3 times
+	for i := 0; i < 3; i++ {
+		n, err := next()
+		if err != nil {
+			continue
+		}
+		req.URL.Host = fmt.Sprintf("%s:%d", n.Address, n.Port)
+		w, err := r.rt.RoundTrip(req)
+		if err != nil {
+			continue
+		}
+		return w, nil
+	}
+
+	return nil, errors.New("failed request")
+}