[master] avoid timeout when assigning for main request with filter by DC or rack (#6291)

* avoid timeout when assigning for main request with filter by DC or rack

https://github.com/seaweedfs/seaweedfs/issues/6290

* use constant NoWritableVolumes

weed/server/master_grpc_server_assign.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"github.com/seaweedfs/seaweedfs/weed/glog"
 	"github.com/seaweedfs/seaweedfs/weed/stats"
+	"strings"
 	"time"
 
 	"github.com/seaweedfs/raft"
@@ -100,6 +101,9 @@ func (ms *MasterServer) Assign(ctx context.Context, req *master_pb.AssignRequest
 			glog.V(1).Infof("assign %v %v: %v", req, option.String(), err)
 			stats.MasterPickForWriteErrorCounter.Inc()
 			lastErr = err
+			if (req.DataCenter != "" || req.Rack != "") && strings.Contains(err.Error(), topology.NoWritableVolumes) {
+				break
+			}
 			time.Sleep(200 * time.Millisecond)
 			continue
 		}