Only backup the predicates belonging to a group.

dgraph/cmd/alpha/admin_backup.go

@@ -114,10 +114,17 @@ func processHttpBackupRequest(ctx context.Context, r *http.Request) error {
 	if err := worker.UpdateMembershipState(ctx); err != nil {
 		return err
 	}
+
+	// Get the current membership state and parse it for easier processing.
 	state := worker.GetMembershipState()
 	var groups []uint32
-	for gid := range state.Groups {
+	predMap := make(map[uint32][]string)
+	for gid, group := range state.Groups {
 		groups = append(groups, gid)
+		predMap[gid] = make([]string, 0)
+		for pred := range group.Tablets {
+			predMap[gid] = append(predMap[gid], pred)
+		}
 	}
 
 	glog.Infof("Created backup request: %s. Groups=%v\n", &req, groups)
@@ -128,6 +135,7 @@ func processHttpBackupRequest(ctx context.Context, r *http.Request) error {
 	for _, gid := range groups {
 		req := req
 		req.GroupId = gid
+		req.Predicates = predMap[gid]
 		go func(req *pb.BackupRequest) {
 			_, err := worker.BackupGroup(ctx, req)
 			errCh <- err
@@ -141,17 +149,7 @@ func processHttpBackupRequest(ctx context.Context, r *http.Request) error {
 		}
 	}
 
-	// Convert state into a map for writing into the manifest.
-	manifestGroups := make(map[uint32][]string)
-	for gid, group := range state.Groups {
-		var preds []string
-		for key := range group.Tablets {
-			preds = append(preds, key)
-		}
-		manifestGroups[gid] = preds
-	}
-
-	m := backup.Manifest{Since: req.ReadTs, Groups: manifestGroups}
+	m := backup.Manifest{Since: req.ReadTs, Groups: predMap}
 	if req.SinceTs == 0 {
 		m.Type = "full"
 		m.BackupId = x.GetRandomName(1)

ee/backup/backup.go

@@ -22,6 +22,7 @@ import (
 
 	"github.com/dgraph-io/badger"
 	"github.com/dgraph-io/dgraph/protos/pb"
+	"github.com/dgraph-io/dgraph/x"
 	"github.com/golang/glog"
 )
 
@@ -45,7 +46,7 @@ type Manifest struct {
 	// because it will become the timestamp from which to backup in the next
 	// incremental backup.
 	Since uint64 `json:"since"`
-	// Groups is the list of valid groups at the time the backup was created.
+	// Groups is the map of valid groups to predicates at the time the backup was created.
 	Groups map[uint32][]string `json:"groups"`
 	// BackupId is a unique ID assigned to all the backups in the same series
 	// (from the first full backup to the last incremental backup).
@@ -87,8 +88,18 @@ func (pr *Processor) WriteBackup(ctx context.Context) (*pb.Status, error) {
 
 	glog.V(3).Infof("Backup manifest version: %d", pr.Request.SinceTs)
 
+	predMap := make(map[string]struct{})
+	for _, pred := range pr.Request.Predicates {
+		predMap[pred] = struct{}{}
+	}
+
 	stream := pr.DB.NewStreamAt(pr.Request.ReadTs)
 	stream.LogPrefix = "Dgraph.Backup"
+	stream.ChooseKey = func(item *badger.Item) bool {
+		parsedKey := x.Parse(item.Key())
+		_, ok := predMap[parsedKey.Attr]
+		return ok
+	}
 	gzWriter := gzip.NewWriter(handler)
 	newSince, err := stream.Backup(gzWriter, pr.Request.SinceTs)
 

protos/pb.proto

@@ -491,6 +491,10 @@ message BackupRequest {
   // True if no credentials should be used to access the S3 or minio bucket.
   // For example, when using a bucket with a public policy.
   bool anonymous = 9;
+
+  // The predicates to backup. All other predicates present in the group (e.g
+  // stale data from a predicate move) will be ignored.
+  repeated string predicates = 10;
 }
 
 message ExportRequest {