randomize same-dc servers and other-dc servers

weed/filer/filechunk_manifest.go

@@ -6,7 +6,6 @@ import (
 	"github.com/chrislusf/seaweedfs/weed/wdclient"
 	"io"
 	"math"
-	"math/rand"
 	"net/url"
 	"strings"
 	"time"
@@ -143,9 +142,6 @@ func retriedStreamFetchChunkData(writer io.Writer, urlStrings []string, cipherKe
 	var shouldRetry bool
 	var totalWritten int
 
-	rand.Shuffle(len(urlStrings), func(i, j int) {
-		urlStrings[i], urlStrings[j] = urlStrings[j], urlStrings[i]
-	})
 	for waitTime := time.Second; waitTime < util.RetryWaitTime; waitTime += waitTime / 2 {
 		for _, urlString := range urlStrings {
 			var localProcesed int

weed/wdclient/vid_map.go

@@ -4,6 +4,7 @@ import (
 	"errors"
 	"fmt"
 	"github.com/chrislusf/seaweedfs/weed/pb"
+	"math/rand"
 	"strconv"
 	"strings"
 	"sync"
@@ -69,13 +70,21 @@ func (vc *vidMap) LookupVolumeServerUrl(vid string) (serverUrls []string, err er
 	if !found {
 		return nil, fmt.Errorf("volume %d not found", id)
 	}
+	var sameDcServers, otherDcServers []string
 	for _, loc := range locations {
 		if vc.DataCenter == "" || loc.DataCenter == "" || vc.DataCenter != loc.DataCenter {
-			serverUrls = append(serverUrls, loc.Url)
+			sameDcServers = append(sameDcServers, loc.Url)
 		} else {
-			serverUrls = append([]string{loc.Url}, serverUrls...)
+			otherDcServers = append(otherDcServers, loc.Url)
 		}
 	}
+	rand.Shuffle(len(sameDcServers), func(i, j int) {
+		sameDcServers[i], sameDcServers[j] = sameDcServers[j], sameDcServers[i]
+	})
+	rand.Shuffle(len(otherDcServers), func(i, j int) {
+		otherDcServers[i], otherDcServers[j] = otherDcServers[j], otherDcServers[i]
+	})
+	serverUrls = append(sameDcServers, otherDcServers...)
 	return
 }