avoid aggressive volume assignment

weed/storage/store.go

@@ -292,7 +292,18 @@ func (s *Store) CollectHeartbeat() *master_pb.Heartbeat {
 	collectionVolumeReadOnlyCount := make(map[string]map[string]uint8)
 	for _, location := range s.Locations {
 		var deleteVids []needle.VolumeId
-		maxVolumeCounts[string(location.DiskType)] += uint32(location.MaxVolumeCount)
+		effectiveMaxCount := location.MaxVolumeCount
+		if location.isDiskSpaceLow {
+			usedSlots := int32(location.LocalVolumesLen())
+			if ecShardCount := location.EcShardCount(); ecShardCount > 0 {
+				usedSlots += int32((ecShardCount + erasure_coding.DataShardsCount - 1) / erasure_coding.DataShardsCount)
+			}
+			effectiveMaxCount = usedSlots
+		}
+		if effectiveMaxCount < 0 {
+			effectiveMaxCount = 0
+		}
+		maxVolumeCounts[string(location.DiskType)] += uint32(effectiveMaxCount)
 		location.volumesLock.RLock()
 		for _, v := range location.volumes {
 			curMaxFileKey, volumeMessage := v.ToVolumeInformationMessage()

weed/storage/store_disk_space_test.go

@@ -4,6 +4,7 @@ import (
 	"testing"
 
 	"github.com/seaweedfs/seaweedfs/weed/storage/needle"
+	"github.com/seaweedfs/seaweedfs/weed/storage/types"
 )
 
 func TestHasFreeDiskLocation(t *testing.T) {
@@ -92,3 +93,31 @@ func TestHasFreeDiskLocation(t *testing.T) {
 		})
 	}
 }
+
+func TestCollectHeartbeatRespectsLowDiskSpace(t *testing.T) {
+	diskType := types.ToDiskType("hdd")
+	location := &DiskLocation{
+		volumes:        make(map[needle.VolumeId]*Volume),
+		isDiskSpaceLow: true,
+		MaxVolumeCount: 10,
+		DiskType:       diskType,
+	}
+	location.volumes[needle.VolumeId(1)] = &Volume{}
+	location.volumes[needle.VolumeId(2)] = &Volume{}
+	location.volumes[needle.VolumeId(3)] = &Volume{}
+
+	store := &Store{
+		Locations: []*DiskLocation{location},
+	}
+
+	hb := store.CollectHeartbeat()
+	if got := hb.MaxVolumeCounts[string(diskType)]; got != 3 {
+		t.Fatalf("expected low disk space to cap max volume count to used slots, got %d", got)
+	}
+
+	location.isDiskSpaceLow = false
+	hb = store.CollectHeartbeat()
+	if got := hb.MaxVolumeCounts[string(diskType)]; got != 10 {
+		t.Fatalf("expected normal disk space to report configured max volume count, got %d", got)
+	}
+}