[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
 		}

weed/topology/topology.go

@@ -254,7 +254,7 @@ func (t *Topology) PickForWrite(requestedCount uint64, option *VolumeGrowOption,
 		return "", 0, nil, shouldGrow, fmt.Errorf("failed to find writable volumes for collection:%s replication:%s ttl:%s error: %v", option.Collection, option.ReplicaPlacement.String(), option.Ttl.String(), err)
 	}
 	if volumeLocationList == nil || volumeLocationList.Length() == 0 {
-		return "", 0, nil, shouldGrow, fmt.Errorf("%s available for collection:%s replication:%s ttl:%s", noWritableVolumes, option.Collection, option.ReplicaPlacement.String(), option.Ttl.String())
+		return "", 0, nil, shouldGrow, fmt.Errorf("%s available for collection:%s replication:%s ttl:%s", NoWritableVolumes, option.Collection, option.ReplicaPlacement.String(), option.Ttl.String())
 	}
 	nextFileId := t.Sequence.NextFileId(requestedCount)
 	fileId = needle.NewFileId(vid, nextFileId, rand.Uint32()).String()

weed/topology/volume_layout.go

@@ -31,7 +31,7 @@ const (
 	readOnlyState     volumeState = "ReadOnly"
 	oversizedState                = "Oversized"
 	crowdedState                  = "Crowded"
-	noWritableVolumes             = "No writable volumes"
+	NoWritableVolumes             = "No writable volumes"
 )
 
 type stateIndicator func(copyState) bool
@@ -302,7 +302,7 @@ func (vl *VolumeLayout) PickForWrite(count uint64, option *VolumeGrowOption) (vi
 
 	lenWriters := len(vl.writables)
 	if lenWriters <= 0 {
-		return 0, 0, nil, true, fmt.Errorf("%s", noWritableVolumes)
+		return 0, 0, nil, true, fmt.Errorf("%s", NoWritableVolumes)
 	}
 	if option.DataCenter == "" && option.Rack == "" && option.DataNode == "" {
 		vid := vl.writables[rand.IntN(lenWriters)]
@@ -337,7 +337,7 @@ func (vl *VolumeLayout) PickForWrite(count uint64, option *VolumeGrowOption) (vi
 			return
 		}
 	}
-	return vid, count, locationList, true, fmt.Errorf("%s in DataCenter:%v Rack:%v DataNode:%v", noWritableVolumes, option.DataCenter, option.Rack, option.DataNode)
+	return vid, count, locationList, true, fmt.Errorf("%s in DataCenter:%v Rack:%v DataNode:%v", NoWritableVolumes, option.DataCenter, option.Rack, option.DataNode)
 }
 
 func (vl *VolumeLayout) HasGrowRequest() bool {