2103: feat(schema): do schema versioning and make backup non-blocking…

… for i… (#7856)

* feat(schema): do schema versioning and make backup non-blocking for indexing (#7852)

Issue:
We used to write schema/types at timestamp=1. That single bit violates the Snapshot Isolation. Hence, we couldn't run schema updates and other operations like backup concurrently. This is an issue in a multi-tenant cluster because if the backup is running we couldn't update the schema.
Fix:
This PR writes the schema/types at the startTs of the transaction and enables the schema updates to be made even if the backup is running.

(cherry picked from commit f376a40)

* fix the predicate move

(cherry picked from commit eb0a04b)

posting/index.go

@@ -574,7 +574,6 @@ func (r *rebuilder) Run(ctx context.Context) error {
 		WithNumVersionsToKeep(math.MaxInt32).
 		WithLogger(&x.ToGlog{}).
 		WithCompression(options.None).
-		WithEncryptionKey(x.WorkerConfig.EncryptionKey).
 		WithLoggingLevel(badger.WARNING).
 		WithMetricsEnabled(false)
 
@@ -1242,14 +1241,14 @@ func DeleteData() error {
 }
 
 // DeletePredicate deletes all entries and indices for a given predicate.
-func DeletePredicate(ctx context.Context, attr string) error {
+func DeletePredicate(ctx context.Context, attr string, ts uint64) error {
 	glog.Infof("Dropping predicate: [%s]", attr)
 	prefix := x.PredicatePrefix(attr)
 	if err := pstore.DropPrefix(prefix); err != nil {
 		return err
 	}
 
-	return schema.State().Delete(attr)
+	return schema.State().Delete(attr, ts)
 }
 
 // DeleteNamespace bans the namespace and deletes its predicates/types from the schema.

protos/pb.proto

@@ -334,6 +334,8 @@ message Proposal {
   RestoreRequest restore = 12;
   CDCState cdc_state = 13;
   DeleteNsRequest delete_ns = 14;  // Used to delete namespace.
+  // Skipping 15 as it is used for uint64 key in master and might be needed later here.
+  uint64 start_ts = 16;
 }
 
 message CDCState {

schema/schema.go

@@ -21,6 +21,7 @@ import (
 	"context"
 	"encoding/hex"
 	"fmt"
+	"math"
 	"sync"
 
 	"github.com/golang/glog"
@@ -96,17 +97,17 @@ func (s *state) DeleteAll() {
 }
 
 // Delete updates the schema in memory and disk
-func (s *state) Delete(attr string) error {
+func (s *state) Delete(attr string, ts uint64) error {
 	s.Lock()
 	defer s.Unlock()
 
 	glog.Infof("Deleting schema for predicate: [%s]", attr)
-	txn := pstore.NewTransactionAt(1, true)
+	txn := pstore.NewTransactionAt(ts, true)
 	if err := txn.Delete(x.SchemaKey(attr)); err != nil {
 		return err
 	}
 	// Delete is called rarely so sync write should be fine.
-	if err := txn.CommitAt(1, nil); err != nil {
+	if err := txn.CommitAt(ts, nil); err != nil {
 		return err
 	}
 
@@ -116,7 +117,7 @@ func (s *state) Delete(attr string) error {
 }
 
 // DeleteType updates the schema in memory and disk
-func (s *state) DeleteType(typeName string) error {
+func (s *state) DeleteType(typeName string, ts uint64) error {
 	if s == nil {
 		return nil
 	}
@@ -125,12 +126,12 @@ func (s *state) DeleteType(typeName string) error {
 	defer s.Unlock()
 
 	glog.Infof("Deleting type definition for type: [%s]", typeName)
-	txn := pstore.NewTransactionAt(1, true)
+	txn := pstore.NewTransactionAt(ts, true)
 	if err := txn.Delete(x.TypeKey(typeName)); err != nil {
 		return err
 	}
 	// Delete is called rarely so sync write should be fine.
-	if err := txn.CommitAt(1, nil); err != nil {
+	if err := txn.CommitAt(ts, nil); err != nil {
 		return err
 	}
 
@@ -466,14 +467,14 @@ func Init(ps *badger.DB) {
 	reset()
 }
 
-// Load reads the schema for the given predicate from the DB.
+// Load reads the latest schema for the given predicate from the DB.
 func Load(predicate string) error {
 	if len(predicate) == 0 {
 		return errors.Errorf("Empty predicate")
 	}
 	delete(State().mutSchema, predicate)
 	key := x.SchemaKey(predicate)
-	txn := pstore.NewTransactionAt(1, false)
+	txn := pstore.NewTransactionAt(math.MaxUint64, false)
 	defer txn.Discard()
 	item, err := txn.Get(key)
 	if err == badger.ErrKeyNotFound || err == badger.ErrBannedKey {
@@ -507,7 +508,7 @@ func LoadFromDb() error {
 // LoadSchemaFromDb iterates through the DB and loads all the stored schema updates.
 func LoadSchemaFromDb() error {
 	prefix := x.SchemaPrefix()
-	txn := pstore.NewTransactionAt(1, false)
+	txn := pstore.NewTransactionAt(math.MaxUint64, false)
 	defer txn.Discard()
 	itr := txn.NewIterator(badger.DefaultIteratorOptions) // Need values, reversed=false.
 	defer itr.Close()
@@ -543,7 +544,7 @@ func LoadSchemaFromDb() error {
 // LoadTypesFromDb iterates through the DB and loads all the stored type updates.
 func LoadTypesFromDb() error {
 	prefix := x.TypePrefix()
-	txn := pstore.NewTransactionAt(1, false)
+	txn := pstore.NewTransactionAt(math.MaxUint64, false)
 	defer txn.Discard()
 	itr := txn.NewIterator(badger.DefaultIteratorOptions) // Need values, reversed=false.
 	defer itr.Close()

systest/backup/encryption/backup_test.go

@@ -104,13 +104,13 @@ func TestBackupMinioE(t *testing.T) {
 	t.Log("Pausing to let zero move tablet...")
 	moveOk := false
 	for retry := 5; retry > 0; retry-- {
-		time.Sleep(3 * time.Second)
 		state, err := testutil.GetStateHttps(testutil.GetAlphaClientConfig(t))
 		require.NoError(t, err)
 		if _, ok := state.Groups["1"].Tablets[tabletName]; ok {
 			moveOk = true
 			break
 		}
+		time.Sleep(1 * time.Second)
 	}
 	require.True(t, moveOk)
 

systest/backup/filesystem/backup_test.go

@@ -209,13 +209,13 @@ func TestBackupFilesystem(t *testing.T) {
 	t.Log("Pausing to let zero move tablet...")
 	moveOk := false
 	for retry := 5; retry > 0; retry-- {
-		time.Sleep(3 * time.Second)
 		state, err := testutil.GetStateHttps(testutil.GetAlphaClientConfig(t))
 		require.NoError(t, err)
 		if _, ok := state.Groups["1"].Tablets[x.NamespaceAttr(x.GalaxyNamespace, "movie")]; ok {
 			moveOk = true
 			break
 		}
+		time.Sleep(1 * time.Second)
 	}
 
 	require.True(t, moveOk)

systest/backup/minio-large/backup_test.go

@@ -110,7 +110,6 @@ func setupTablets(t *testing.T, dg *dgo.Dgraph) {
 	t.Log("Pausing to let zero move tablets...")
 	moveOk := false
 	for retry := 5; retry > 0; retry-- {
-		time.Sleep(3 * time.Second)
 		state, err := testutil.GetStateHttps(testutil.GetAlphaClientConfig(t))
 		require.NoError(t, err)
 		_, ok1 := state.Groups["1"].Tablets[x.GalaxyAttr("name1")]
@@ -120,6 +119,7 @@ func setupTablets(t *testing.T, dg *dgo.Dgraph) {
 			moveOk = true
 			break
 		}
+		time.Sleep(1 * time.Second)
 	}
 	require.True(t, moveOk)
 }

systest/backup/minio/backup_test.go

@@ -99,13 +99,13 @@ func TestBackupMinio(t *testing.T) {
 	t.Log("Pausing to let zero move tablet...")
 	moveOk := false
 	for retry := 5; retry > 0; retry-- {
-		time.Sleep(3 * time.Second)
 		state, err := testutil.GetStateHttps(testutil.GetAlphaClientConfig(t))
 		require.NoError(t, err)
 		if _, ok := state.Groups["1"].Tablets[x.NamespaceAttr(x.GalaxyNamespace, "movie")]; ok {
 			moveOk = true
 			break
 		}
+		time.Sleep(1 * time.Second)
 	}
 	require.True(t, moveOk)
 

testutil/backup.go

@@ -20,6 +20,7 @@ import (
 	"context"
 	"fmt"
 	"io/ioutil"
+	"math"
 	"net/http"
 	"strings"
 	"testing"
@@ -178,8 +179,7 @@ func readSchema(pdir string, dType dataType) ([]string, error) {
 	defer db.Close()
 	values := make([]string, 0)
 
-	// Predicates and types in the schema are written with timestamp 1.
-	txn := db.NewTransactionAt(1, false)
+	txn := db.NewTransactionAt(math.MaxUint64, false)
 	defer txn.Discard()
 	itr := txn.NewIterator(badger.DefaultIteratorOptions)
 	defer itr.Close()

worker/backup_ee.go

@@ -52,7 +52,7 @@ func backupCurrentGroup(ctx context.Context, req *pb.BackupRequest) (*pb.BackupR
 		return nil, err
 	}
 
-	closer, err := g.Node.startTask(opBackup)
+	closer, err := g.Node.startTaskAtTs(opBackup, req.ReadTs)
 	if err != nil {
 		return nil, errors.Wrapf(err, "cannot start backup operation")
 	}

worker/backup_processor.go

@@ -236,8 +236,7 @@ func (pr *BackupProcessor) WriteBackup(ctx context.Context) (*pb.BackupResponse,
 		}
 		defer tl.alloc.Release()
 
-		// Schema and types are written at Ts=1.
-		txn := pr.DB.NewTransactionAt(1, false)
+		txn := pr.DB.NewTransactionAt(pr.Request.ReadTs, false)
 		defer txn.Discard()
 		// We don't need to iterate over all versions.
 		iopts := badger.DefaultIteratorOptions