opt(stream): add option to directly copy over tables from lower levels (

dgraph-io#1700)

This PR adds FullCopy option in Stream. This allows sending the table entirely to the writer. If this option is set to true we directly copy over the tables from the last 2 levels. This option increases the stream speed while also lowering the memory consumption on the DB that is streaming the KVs.
For 71GB, compressed and encrypted DB we observed 3x improvement in speed. The DB contained ~65GB in the last 2 levels while remaining in the above levels.

To use this option, the following options should be set in Stream.

stream.KeyToList = nil
stream.ChooseKey = nil
stream.SinceTs = 0
db.managedTxns = true

If we use stream writer for receiving the KVs, the encryption mode has to be the same in sender and receiver. This will restrict db.StreamDB() to use the same encryption mode in both input and output DB. Added TODO for allowing different encryption modes.

badger/cmd/stream.go

@@ -117,6 +117,7 @@ func stream(cmd *cobra.Command, args []string) error {
 			WithValueDir(so.outDir).
 			WithNumVersionsToKeep(so.numVersions).
 			WithCompression(options.CompressionType(so.compressionType)).
+			WithEncryptionKey(encKey).
 			WithReadOnly(false)
 		err = inDB.StreamDB(outOpt)
 

db.go

@@ -813,13 +813,10 @@ func (db *DB) writeRequests(reqs []*request) error {
 		}
 	}
 	db.opt.Debugf("writeRequests called. Writing to value log")
-	if !db.opt.managedTxns {
-		// Don't do value log writes in managed mode.
-		err := db.vlog.write(reqs)
-		if err != nil {
-			done(err)
-			return err
-		}
+	err := db.vlog.write(reqs)
+	if err != nil {
+		done(err)
+		return err
 	}
 
 	db.opt.Debugf("Sending updates to subscribers")
@@ -2194,6 +2191,7 @@ func (db *DB) StreamDB(outOptions Options) error {
 	// Stream contents of DB to the output DB.
 	stream := db.NewStreamAt(math.MaxUint64)
 	stream.LogPrefix = fmt.Sprintf("Streaming DB to new DB at %s", outDir)
+	stream.FullCopy = true
 
 	stream.Send = func(buf *z.Buffer) error {
 		return writer.Write(buf)

iterator.go

@@ -368,17 +368,17 @@ func (opt *IteratorOptions) pickTable(t table.TableInterface) bool {
 // that the tables are sorted in the right order.
 func (opt *IteratorOptions) pickTables(all []*table.Table) []*table.Table {
 	filterTables := func(tables []*table.Table) []*table.Table {
-		if opt.SinceTs > 0 {
-			tmp := tables[:0]
-			for _, t := range tables {
-				if t.MaxVersion() < opt.SinceTs {
-					continue
-				}
-				tmp = append(tmp, t)
+		if opt.SinceTs == 0 {
+			return tables
+		}
+		out := tables[:0]
+		for _, t := range tables {
+			if t.MaxVersion() < opt.SinceTs {
+				continue
 			}
-			tables = tmp
+			out = append(out, t)
 		}
-		return tables
+		return out
 	}
 
 	if len(opt.Prefix) == 0 {
@@ -492,7 +492,7 @@ func (txn *Txn) NewIterator(opt IteratorOptions) *Iterator {
 	for i := 0; i < len(tables); i++ {
 		iters = append(iters, tables[i].sl.NewUniIterator(opt.Reverse))
 	}
-	iters = txn.db.lc.appendIterators(iters, &opt) // This will increment references.
+	iters = append(iters, txn.db.lc.iterators(&opt)...) // This will increment references.
 	res := &Iterator{
 		txn:    txn,
 		iitr:   table.NewMergeIterator(iters, opt.Reverse),

key_registry.go

@@ -30,6 +30,7 @@ import (
 
 	"github.com/dgraph-io/badger/v3/pb"
 	"github.com/dgraph-io/badger/v3/y"
+	"github.com/pkg/errors"
 )
 
 const (
@@ -264,7 +265,7 @@ func WriteKeyRegistry(reg *KeyRegistry, opt KeyRegistryOptions) error {
 	// Write all the datakeys to the buf.
 	for _, k := range reg.dataKeys {
 		// Writing the datakey to the given buffer.
-		if err := storeDataKey(buf, opt.EncryptionKey, k); err != nil {
+		if err := storeDataKey(buf, opt.EncryptionKey, *k); err != nil {
 			return y.Wrapf(err, "Error while storing datakey in WriteKeyRegistry")
 		}
 	}
@@ -338,44 +339,58 @@ func (kr *KeyRegistry) LatestDataKey() (*pb.DataKey, error) {
 	defer kr.Unlock()
 	// Key might have generated by another go routine. So,
 	// checking once again.
-	key, valid = validKey()
-	if valid {
+	if key, valid := validKey(); valid {
 		return key, nil
 	}
 	k := make([]byte, len(kr.opt.EncryptionKey))
 	iv, err := y.GenerateIV()
 	if err != nil {
 		return nil, err
 	}
-	_, err = rand.Read(k)
-	if err != nil {
+
+	if _, err = rand.Read(k); err != nil {
 		return nil, err
 	}
 	// Otherwise Increment the KeyID and generate new datakey.
 	kr.nextKeyID++
-	dk := &pb.DataKey{
+	dk := pb.DataKey{
 		KeyId:     kr.nextKeyID,
 		Data:      k,
 		CreatedAt: time.Now().Unix(),
 		Iv:        iv,
 	}
+	kr.lastCreated = dk.CreatedAt
+	kr.dataKeys[kr.nextKeyID] = &dk
 	// Don't store the datakey on file if badger is running in InMemory mode.
-	if !kr.opt.InMemory {
-		// Store the datekey.
-		buf := &bytes.Buffer{}
-		if err = storeDataKey(buf, kr.opt.EncryptionKey, dk); err != nil {
-			return nil, err
-		}
-		// Persist the datakey to the disk
-		if _, err = kr.fp.Write(buf.Bytes()); err != nil {
-			return nil, err
-		}
+	if kr.opt.InMemory {
+		return &dk, nil
+
 	}
-	// storeDatakey encrypts the datakey So, placing un-encrypted key in the memory.
-	dk.Data = k
-	kr.lastCreated = dk.CreatedAt
-	kr.dataKeys[kr.nextKeyID] = dk
-	return dk, nil
+	// Store the datekey.
+	if err = storeDataKey(kr.fp, kr.opt.EncryptionKey, dk); err != nil {
+		return nil, err
+	}
+	return &dk, nil
+}
+
+func (kr *KeyRegistry) AddKey(dk pb.DataKey) (uint64, error) {
+	// If we don't have a encryption key, we cannot store the datakey.
+	if len(kr.opt.EncryptionKey) == 0 {
+		return 0, errors.New("No encryption key found. Cannot add data key")
+	}
+
+	if _, ok := kr.dataKeys[dk.KeyId]; !ok {
+		// If KeyId does not exists already, then use the next available KeyId to store data key.
+		kr.nextKeyID++
+		dk.KeyId = kr.nextKeyID
+	}
+	kr.dataKeys[dk.KeyId] = &dk
+
+	if kr.opt.InMemory {
+		return dk.KeyId, nil
+	}
+	// Store the datakey.
+	return dk.KeyId, storeDataKey(kr.fp, kr.opt.EncryptionKey, dk)
 }
 
 // Close closes the key registry.
@@ -387,38 +402,30 @@ func (kr *KeyRegistry) Close() error {
 }
 
 // storeDataKey stores datakey in an encrypted format in the given buffer. If storage key preset.
-func storeDataKey(buf *bytes.Buffer, storageKey []byte, k *pb.DataKey) error {
+// DO NOT use a pointer for key. storeDataKey modifies the kv.Data field.
+func storeDataKey(w io.Writer, storageKey []byte, key pb.DataKey) error {
 	// xor will encrypt the IV and xor with the given data.
 	// It'll used for both encryption and decryption.
 	xor := func() error {
 		if len(storageKey) == 0 {
 			return nil
 		}
 		var err error
-		k.Data, err = y.XORBlockAllocate(k.Data, storageKey, k.Iv)
+		key.Data, err = y.XORBlockAllocate(key.Data, storageKey, key.Iv)
 		return err
 	}
 	// In memory datakey will be plain text so encrypting before storing to the disk.
-	var err error
-	if err = xor(); err != nil {
+	if err := xor(); err != nil {
 		return y.Wrapf(err, "Error while encrypting datakey in storeDataKey")
 	}
-	var data []byte
-	if data, err = k.Marshal(); err != nil {
-		err = y.Wrapf(err, "Error while marshaling datakey in storeDataKey")
-		var err2 error
-		// decrypting the datakey back.
-		if err2 = xor(); err2 != nil {
-			return y.Wrapf(err,
-				y.Wrapf(err2, "Error while decrypting datakey in storeDataKey").Error())
-		}
-		return err
+	data, err := key.Marshal()
+	if err != nil {
+		return y.Wrapf(err, "Error while marshaling datakey in storeDataKey")
 	}
 	var lenCrcBuf [8]byte
 	binary.BigEndian.PutUint32(lenCrcBuf[0:4], uint32(len(data)))
 	binary.BigEndian.PutUint32(lenCrcBuf[4:8], crc32.Checksum(data, y.CastagnoliCrcTable))
-	y.Check2(buf.Write(lenCrcBuf[:]))
-	y.Check2(buf.Write(data))
-	// Decrypting the datakey back since we're using the pointer.
-	return xor()
+	y.Check2(w.Write(lenCrcBuf[:]))
+	y.Check2(w.Write(data))
+	return nil
 }

level_handler.go

@@ -304,9 +304,9 @@ func (s *levelHandler) get(key []byte) (y.ValueStruct, error) {
 	return maxVs, decr()
 }
 
-// appendIterators appends iterators to an array of iterators, for merging.
+// iterators returns an array of iterators, for merging.
 // Note: This obtains references for the table handlers. Remember to close these iterators.
-func (s *levelHandler) appendIterators(iters []y.Iterator, opt *IteratorOptions) []y.Iterator {
+func (s *levelHandler) iterators(opt *IteratorOptions) []y.Iterator {
 	s.RLock()
 	defer s.RUnlock()
 
@@ -324,14 +324,41 @@ func (s *levelHandler) appendIterators(iters []y.Iterator, opt *IteratorOptions)
 				out = append(out, t)
 			}
 		}
-		return appendIteratorsReversed(iters, out, topt)
+		return iteratorsReversed(out, topt)
 	}
 
 	tables := opt.pickTables(s.tables)
 	if len(tables) == 0 {
-		return iters
+		return nil
 	}
-	return append(iters, table.NewConcatIterator(tables, topt))
+	return []y.Iterator{table.NewConcatIterator(tables, topt)}
+}
+
+func (s *levelHandler) getTables(opt *IteratorOptions) []*table.Table {
+	if opt.Reverse {
+		panic("Invalid option for getTables")
+	}
+
+	// Typically this would only be called for the last level.
+	s.RLock()
+	defer s.RUnlock()
+
+	if s.level == 0 {
+		var out []*table.Table
+		for _, t := range s.tables {
+			if opt.pickTable(t) {
+				t.IncrRef()
+				out = append(out, t)
+			}
+		}
+		return out
+	}
+
+	tables := opt.pickTables(s.tables)
+	for _, t := range tables {
+		t.IncrRef()
+	}
+	return tables
 }
 
 type levelHandlerRLocked struct{}

levels.go

@@ -32,6 +32,7 @@ import (
 
 	otrace "go.opencensus.io/trace"
 
+	"github.com/dgraph-io/badger/v3/options"
 	"github.com/dgraph-io/badger/v3/pb"
 	"github.com/dgraph-io/badger/v3/table"
 	"github.com/dgraph-io/badger/v3/y"
@@ -900,7 +901,7 @@ func (s *levelsController) compactBuildTables(
 		var iters []y.Iterator
 		switch {
 		case lev == 0:
-			iters = appendIteratorsReversed(iters, topTables, table.NOCACHE)
+			iters = append(iters, iteratorsReversed(topTables, table.NOCACHE)...)
 		case len(topTables) > 0:
 			y.AssertTrue(len(topTables) == 1)
 			iters = []y.Iterator{topTables[0].NewIterator(table.NOCACHE)}
@@ -1606,24 +1607,34 @@ func (s *levelsController) get(key []byte, maxVs y.ValueStruct, startLevel int)
 	return maxVs, nil
 }
 
-func appendIteratorsReversed(out []y.Iterator, th []*table.Table, opt int) []y.Iterator {
+func iteratorsReversed(th []*table.Table, opt int) []y.Iterator {
+	out := make([]y.Iterator, 0, len(th))
 	for i := len(th) - 1; i >= 0; i-- {
 		// This will increment the reference of the table handler.
 		out = append(out, th[i].NewIterator(opt))
 	}
 	return out
 }
 
-// appendIterators appends iterators to an array of iterators, for merging.
+// getTables return tables from all levels. It would call IncrRef on all returned tables.
+func (s *levelsController) getTables(opt *IteratorOptions) [][]*table.Table {
+	res := make([][]*table.Table, 0, len(s.levels))
+	for _, level := range s.levels {
+		res = append(res, level.getTables(opt))
+	}
+	return res
+}
+
+// iterators returns an array of iterators, for merging.
 // Note: This obtains references for the table handlers. Remember to close these iterators.
-func (s *levelsController) appendIterators(
-	iters []y.Iterator, opt *IteratorOptions) []y.Iterator {
+func (s *levelsController) iterators(opt *IteratorOptions) []y.Iterator {
 	// Just like with get, it's important we iterate the levels from 0 on upward, to avoid missing
 	// data when there's a compaction.
+	itrs := make([]y.Iterator, 0, len(s.levels))
 	for _, level := range s.levels {
-		iters = level.appendIterators(iters, opt)
+		itrs = append(itrs, level.iterators(opt)...)
 	}
-	return iters
+	return itrs
 }
 
 // TableInfo represents the information about a table.
@@ -1750,3 +1761,46 @@ func (s *levelsController) keySplits(numPerTable int, prefix []byte) []string {
 	sort.Strings(splits)
 	return splits
 }
+
+// AddTable builds the table from the KV.value options passed through the KV.Key.
+func (lc *levelsController) AddTable(
+	kv *pb.KV, lev int, dk *pb.DataKey, change *pb.ManifestChange) error {
+	// TODO: Encryption / Decryption might be required for the table, if the sender and receiver
+	// don't have same encryption mode. See if inplace encryption/decryption can be done.
+	// Tables are sent in the sorted order, so no need to sort them here.
+	encrypted := len(lc.kv.opt.EncryptionKey) > 0
+	y.AssertTrue((dk != nil && encrypted) || (dk == nil && !encrypted))
+	// The keyId is zero if there is no encryption.
+	opts := buildTableOptions(lc.kv)
+	opts.Compression = options.CompressionType(change.Compression)
+	opts.DataKey = dk
+
+	fileID := lc.reserveFileID()
+	fname := table.NewFilename(fileID, lc.kv.opt.Dir)
+
+	// kv.Value is owned by the z.buffer. Ensure that we copy this buffer.
+	var tbl *table.Table
+	var err error
+	if lc.kv.opt.InMemory {
+		if tbl, err = table.OpenInMemoryTable(y.Copy(kv.Value), fileID, &opts); err != nil {
+			return errors.Wrap(err, "while creating in-memory table from buffer")
+		}
+	} else {
+		if tbl, err = table.CreateTableFromBuffer(fname, kv.Value, opts); err != nil {
+			return errors.Wrap(err, "while creating table from buffer")
+		}
+	}
+
+	lc.levels[lev].addTable(tbl)
+	// Release the ref held by OpenTable. addTable would add a reference.
+	_ = tbl.DecrRef()
+
+	change.Id = fileID
+	change.Level = uint32(lev)
+	if dk != nil {
+		change.KeyId = dk.KeyId
+	}
+	// We use the same data KeyId. So, change.KeyId remains the same.
+	y.AssertTrue(change.Op == pb.ManifestChange_CREATE)
+	return lc.kv.manifest.addChanges([]*pb.ManifestChange{change})
+}