Randomize http redirect.

Randomize http redirect.
Also remove unnecessary empty string checking.

go/weed/weed_server/master_server_handlers_admin.go

@@ -5,6 +5,7 @@ import (
 	"errors"
 	"fmt"
 	"io/ioutil"
+	"math/rand"
 	"net/http"
 	"strconv"
 	"strings"
@@ -122,11 +123,7 @@ func (ms *MasterServer) redirectHandler(w http.ResponseWriter, r *http.Request)
 	}
 	machines := ms.Topo.Lookup("", volumeId)
 	if machines != nil && len(machines) > 0 {
-		url := machines[0].PublicUrl
-		if url == "" {
-			url = machines[0].Url()
-		}
-		http.Redirect(w, r, "http://"+url+r.URL.Path, http.StatusMovedPermanently)
+		http.Redirect(w, r, "http://"+machines[rand.Intn(len(machines))].PublicUrl+r.URL.Path, http.StatusMovedPermanently)
 	} else {
 		writeJsonError(w, r, http.StatusNotFound, fmt.Errorf("volume id %d not found.", volumeId))
 	}