filer.remote.sync: exit when directory is unmounted

this will not propagate the deletions back to the cloud

weed/remote_storage/track_sync_offset.go

@@ -0,0 +1,73 @@
+package remote_storage
+
+import (
+	"context"
+	"errors"
+	"github.com/chrislusf/seaweedfs/weed/pb"
+	"github.com/chrislusf/seaweedfs/weed/pb/filer_pb"
+	"github.com/chrislusf/seaweedfs/weed/util"
+	"google.golang.org/grpc"
+)
+
+const (
+	SyncKeyPrefix = "remote.sync."
+)
+
+func GetSyncOffset(grpcDialOption grpc.DialOption, filer string, dir string) (lastOffsetTsNs int64, readErr error) {
+
+	dirHash := uint32(util.HashStringToLong(dir))
+
+	readErr = pb.WithFilerClient(filer, grpcDialOption, func(client filer_pb.SeaweedFilerClient) error {
+		syncKey := []byte(SyncKeyPrefix + "____")
+		util.Uint32toBytes(syncKey[len(SyncKeyPrefix):len(SyncKeyPrefix)+4], dirHash)
+
+		resp, err := client.KvGet(context.Background(), &filer_pb.KvGetRequest{Key: syncKey})
+		if err != nil {
+			return err
+		}
+
+		if len(resp.Error) != 0 {
+			return errors.New(resp.Error)
+		}
+		if len(resp.Value) < 8 {
+			return nil
+		}
+
+		lastOffsetTsNs = int64(util.BytesToUint64(resp.Value))
+
+		return nil
+	})
+
+	return
+
+}
+
+func SetSyncOffset(grpcDialOption grpc.DialOption, filer string, dir string, offsetTsNs int64) error {
+
+	dirHash := uint32(util.HashStringToLong(dir))
+
+	return pb.WithFilerClient(filer, grpcDialOption, func(client filer_pb.SeaweedFilerClient) error {
+
+		syncKey := []byte(SyncKeyPrefix + "____")
+		util.Uint32toBytes(syncKey[len(SyncKeyPrefix):len(SyncKeyPrefix)+4], dirHash)
+
+		valueBuf := make([]byte, 8)
+		util.Uint64toBytes(valueBuf, uint64(offsetTsNs))
+
+		resp, err := client.KvPut(context.Background(), &filer_pb.KvPutRequest{
+			Key:   syncKey,
+			Value: valueBuf,
+		})
+		if err != nil {
+			return err
+		}
+
+		if len(resp.Error) != 0 {
+			return errors.New(resp.Error)
+		}
+
+		return nil
+
+	})
+
+}