master: add configurable volume growth toml setting

weed/command/scaffold.go

@@ -369,6 +369,8 @@ type = "memory"     # Choose [memory|etcd] type for storing the file id sequence
 sequencer_etcd_urls = "http://127.0.0.1:2379"
 
 
+# configurations for tiered cloud storage
+# old volumes are transparently moved to cloud for cost efficiency
 [storage.backend]
 	[storage.backend.s3.default]
 	enabled = false
@@ -377,5 +379,12 @@ sequencer_etcd_urls = "http://127.0.0.1:2379"
 	region = "us-east-2"
 	bucket = "your_bucket_name"    # an existing bucket
 
+# create this number of logical volumes if no more writable volumes
+[master.volume_growth]
+count_1 = 7                # create 1 x 7 = 7 actual volumes
+count_2 = 6                # create 2 x 6 = 12 actual volumes
+count_3 = 3                # create 3 x 3 = 9 actual volumes
+count_other = 1            # create n x 1 = n actual volumes
+
 `
 )

weed/topology/volume_growth.go

@@ -7,6 +7,7 @@ import (
 
 	"github.com/chrislusf/seaweedfs/weed/storage/needle"
 	"github.com/chrislusf/seaweedfs/weed/storage/super_block"
+	"github.com/chrislusf/seaweedfs/weed/util"
 
 	"google.golang.org/grpc"
 
@@ -48,15 +49,20 @@ func NewDefaultVolumeGrowth() *VolumeGrowth {
 // one replication type may need rp.GetCopyCount() actual volumes
 // given copyCount, how many logical volumes to create
 func (vg *VolumeGrowth) findVolumeCount(copyCount int) (count int) {
+	v := util.GetViper()
+	v.SetDefault("master.volume_growth.copy_1", 7)
+	v.SetDefault("master.volume_growth.copy_2", 6)
+	v.SetDefault("master.volume_growth.copy_3", 3)
+	v.SetDefault("master.volume_growth.copy_other", 1)
 	switch copyCount {
 	case 1:
-		count = 7
+		count = v.GetInt("master.volume_growth.copy_1")
 	case 2:
-		count = 6
+		count = v.GetInt("master.volume_growth.copy_2")
 	case 3:
-		count = 3
+		count = v.GetInt("master.volume_growth.copy_3")
 	default:
-		count = 1
+		count = v.GetInt("master.volume_growth.copy_other")
 	}
 	return
 }