backup,restore: support backing up / restore system databases (#1048) (…

…#1078)

cmd/br/backup.go

@@ -109,7 +109,7 @@ func newFullBackupCommand() *cobra.Command {
 			return runBackupCommand(command, "Full backup")
 		},
 	}
-	task.DefineFilterFlags(command)
+	task.DefineFilterFlags(command, acceptAllTables)
 	return command
 }
 

cmd/br/cmd.go

@@ -32,6 +32,20 @@ var (
 	hasLogFile      uint64
 	tidbGlue        = gluetidb.New()
 	envLogToTermKey = "BR_LOG_TO_TERM"
+
+	filterOutSysAndMemTables = []string{
+		"*.*",
+		fmt.Sprintf("!%s.*", utils.TemporaryDBName("*")),
+		"!mysql.*",
+		"!sys.*",
+		"!INFORMATION_SCHEMA.*",
+		"!PERFORMANCE_SCHEMA.*",
+		"!METRICS_SCHEMA.*",
+		"!INSPECTION_SCHEMA.*",
+	}
+	acceptAllTables = []string{
+		"*.*",
+	}
 )
 
 const (

cmd/br/restore.go

@@ -120,7 +120,7 @@ func newFullRestoreCommand() *cobra.Command {
 			return runRestoreCommand(cmd, "Full restore")
 		},
 	}
-	task.DefineFilterFlags(command)
+	task.DefineFilterFlags(command, filterOutSysAndMemTables)
 	return command
 }
 
@@ -159,7 +159,7 @@ func newLogRestoreCommand() *cobra.Command {
 			return runLogRestoreCommand(cmd)
 		},
 	}
-	task.DefineFilterFlags(command)
+	task.DefineFilterFlags(command, filterOutSysAndMemTables)
 	task.DefineLogRestoreFlags(command)
 	return command
 }

errors.toml

@@ -196,3 +196,8 @@ error = '''
 failed to write and ingest
 '''
 
+["BR:Restore:ErrUnsupportedSysTable"]
+error = '''
+the system table isn't supported for restoring yet
+'''
+

pkg/backup/client.go

@@ -302,7 +302,7 @@ func BuildBackupRangeAndSchema(
 
 	for _, dbInfo := range dbs {
 		// skip system databases
-		if util.IsMemOrSysDB(dbInfo.Name.L) {
+		if !tableFilter.MatchSchema(dbInfo.Name.O) || util.IsMemDB(dbInfo.Name.L) {
 			continue
 		}
 

pkg/backup/schema.go

@@ -130,6 +130,9 @@ func (ss *Schemas) BackupSchemas(
 
 	schemas := make([]*backuppb.Schema, 0, len(ss.schemas))
 	for name, schema := range ss.schemas {
+		if utils.IsSysDB(schema.dbInfo.Name.L) {
+			schema.dbInfo.Name = utils.TemporaryDBName(schema.dbInfo.Name.O)
+		}
 		dbBytes, err := json.Marshal(schema.dbInfo)
 		if err != nil {
 			return nil, errors.Trace(err)

pkg/backup/schema_test.go

@@ -73,7 +73,8 @@ func (s *testBackupSchemaSuite) TestBuildBackupRangeAndSchema(c *C) {
 	c.Assert(backupSchemas, IsNil)
 
 	// Empty database.
-	noFilter, err := filter.Parse([]string{"*.*"})
+	// Filter out system tables manually.
+	noFilter, err := filter.Parse([]string{"*.*", "!mysql.*"})
 	c.Assert(err, IsNil)
 	_, backupSchemas, err = backup.BuildBackupRangeAndSchema(
 		s.mock.Storage, noFilter, math.MaxUint64)

pkg/errors/errors.go

@@ -44,6 +44,7 @@ var (
 	ErrRestoreInvalidRange     = errors.Normalize("invalid restore range", errors.RFCCodeText("BR:Restore:ErrRestoreInvalidRange"))
 	ErrRestoreWriteAndIngest   = errors.Normalize("failed to write and ingest", errors.RFCCodeText("BR:Restore:ErrRestoreWriteAndIngest"))
 	ErrRestoreSchemaNotExists  = errors.Normalize("schema not exists", errors.RFCCodeText("BR:Restore:ErrRestoreSchemaNotExists"))
+	ErrUnsupportedSystemTable  = errors.Normalize("the system table isn't supported for restoring yet", errors.RFCCodeText("BR:Restore:ErrUnsupportedSysTable"))
 
 	// TODO maybe it belongs to PiTR.
 	ErrRestoreRTsConstrain = errors.Normalize("resolved ts constrain violation", errors.RFCCodeText("BR:Restore:ErrRestoreResolvedTsConstrain"))

pkg/gluetidb/glue.go

@@ -105,7 +105,7 @@ func (g Glue) GetVersion() string {
 
 // Execute implements glue.Session.
 func (gs *tidbSession) Execute(ctx context.Context, sql string) error {
-	_, err := gs.se.Execute(ctx, sql)
+	_, err := gs.se.ExecuteInternal(ctx, sql)
 	return errors.Trace(err)
 }
 

pkg/restore/systable_restore.go

@@ -0,0 +1,185 @@
+// Copyright 2020 PingCAP, Inc. Licensed under Apache-2.0.
+
+package restore
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/pingcap/errors"
+	"github.com/pingcap/log"
+	"github.com/pingcap/parser/model"
+	"github.com/pingcap/parser/mysql"
+	filter "github.com/pingcap/tidb-tools/pkg/table-filter"
+	"go.uber.org/multierr"
+	"go.uber.org/zap"
+
+	berrors "github.com/pingcap/br/pkg/errors"
+	"github.com/pingcap/br/pkg/logutil"
+	"github.com/pingcap/br/pkg/utils"
+)
+
+var statsTables = map[string]struct{}{
+	"stats_buckets":    {},
+	"stats_extended":   {},
+	"stats_feedback":   {},
+	"stats_fm_sketch":  {},
+	"stats_histograms": {},
+	"stats_meta":       {},
+	"stats_top_n":      {},
+}
+
+func isStatsTable(tableName string) bool {
+	_, ok := statsTables[tableName]
+	return ok
+}
+
+// RestoreSystemSchemas restores the system schema(i.e. the `mysql` schema).
+// Detail see https://github.com/pingcap/br/issues/679#issuecomment-762592254.
+func (rc *Client) RestoreSystemSchemas(ctx context.Context, f filter.Filter) {
+	sysDB := mysql.SystemDB
+
+	temporaryDB := utils.TemporaryDBName(sysDB)
+	defer rc.cleanTemporaryDatabase(ctx, sysDB)
+
+	if !f.MatchSchema(temporaryDB.O) {
+		log.Debug("system database filtered out", zap.String("database", sysDB))
+		return
+	}
+	originDatabase, ok := rc.databases[temporaryDB.O]
+	if !ok {
+		log.Info("system database not backed up, skipping", zap.String("database", sysDB))
+		return
+	}
+	db, ok := rc.getDatabaseByName(sysDB)
+	if !ok {
+		// Or should we create the database here?
+		log.Warn("target database not exist, aborting", zap.String("database", sysDB))
+		return
+	}
+
+	tablesRestored := make([]string, 0, len(originDatabase.Tables))
+	for _, table := range originDatabase.Tables {
+		tableName := table.Info.Name
+		if f.MatchTable(sysDB, tableName.O) {
+			if err := rc.replaceTemporaryTableToSystable(ctx, tableName.L, db); err != nil {
+				logutil.WarnTerm("error during merging temporary tables into system tables",
+					logutil.ShortError(err),
+					zap.Stringer("table", tableName),
+				)
+			}
+		}
+		tablesRestored = append(tablesRestored, tableName.L)
+	}
+	if err := rc.afterSystemTablesReplaced(ctx, tablesRestored); err != nil {
+		for _, e := range multierr.Errors(err) {
+			logutil.WarnTerm("error during reconfigurating the system tables", zap.String("database", sysDB), logutil.ShortError(e))
+		}
+	}
+}
+
+// database is a record of a database.
+// For fast querying whether a table exists and the temporary database of it.
+type database struct {
+	ExistingTables map[string]*model.TableInfo
+	Name           model.CIStr
+	TemporaryName  model.CIStr
+}
+
+// getDatabaseByName make a record of a database from info schema by its name.
+func (rc *Client) getDatabaseByName(name string) (*database, bool) {
+	infoSchema := rc.dom.InfoSchema()
+	schema, ok := infoSchema.SchemaByName(model.NewCIStr(name))
+	if !ok {
+		return nil, false
+	}
+	db := &database{
+		ExistingTables: map[string]*model.TableInfo{},
+		Name:           model.NewCIStr(name),
+		TemporaryName:  utils.TemporaryDBName(name),
+	}
+	for _, t := range schema.Tables {
+		db.ExistingTables[t.Name.L] = t
+	}
+	return db, true
+}
+
+// afterSystemTablesReplaced do some extra work for special system tables.
+// e.g. after inserting to the table mysql.user, we must execute `FLUSH PRIVILEGES` to allow it take effect.
+func (rc *Client) afterSystemTablesReplaced(ctx context.Context, tables []string) error {
+	var err error
+	for _, table := range tables {
+		switch {
+		case table == "user":
+			// We cannot execute `rc.dom.NotifyUpdatePrivilege` here, because there isn't
+			// sessionctx.Context provided by the glue.
+			// TODO: update the glue type and allow we retrive a session context from it.
+			err = multierr.Append(err, errors.Annotatef(berrors.ErrUnsupportedSystemTable,
+				"restored user info may not take effect, until you should execute `FLUSH PRIVILEGES` manually"))
+		}
+	}
+	return err
+}
+
+// replaceTemporaryTableToSystable replaces the temporary table to real system table.
+func (rc *Client) replaceTemporaryTableToSystable(ctx context.Context, tableName string, db *database) error {
+	execSQL := func(sql string) error {
+		// SQLs here only contain table name and database name, seems it is no need to redact them.
+		if err := rc.db.se.Execute(ctx, sql); err != nil {
+			log.Warn("failed to execute SQL restore system database",
+				zap.String("table", tableName),
+				zap.Stringer("database", db.Name),
+				zap.String("sql", sql),
+				zap.Error(err),
+			)
+			return berrors.ErrUnknown.Wrap(err).GenWithStack("failed to execute %s", sql)
+		}
+		log.Info("successfully restore system database",
+			zap.String("table", tableName),
+			zap.Stringer("database", db.Name),
+			zap.String("sql", sql),
+		)
+		return nil
+	}
+
+	// The newly created tables have different table IDs with original tables,
+	// 	hence the old statistics are invalid.
+	//
+	// TODO:
+	// 	1   ) Rewrite the table IDs via `UPDATE _temporary_mysql.stats_xxx SET table_id = new_table_id WHERE table_id = old_table_id`
+	//		BEFORE replacing into and then execute `rc.statsHandler.Update(rc.dom.InfoSchema())`.
+	//  1.5 ) (Optional) The UPDATE statement sometimes costs, the whole system tables restore step can be place into the restore pipeline.
+	//  2   ) Deprecate the origin interface for backing up statistics.
+	if isStatsTable(tableName) {
+		return berrors.ErrUnsupportedSystemTable.GenWithStack("restoring stats via `mysql` schema isn't support yet: " +
+			"the table ID is out-of-date and may corrupt existing statistics")
+	}
+
+	if db.ExistingTables[tableName] != nil {
+		log.Info("table existing, using replace into for restore",
+			zap.String("table", tableName),
+			zap.Stringer("schema", db.Name))
+		replaceIntoSQL := fmt.Sprintf("REPLACE INTO %s SELECT * FROM %s;",
+			utils.EncloseDBAndTable(db.Name.L, tableName),
+			utils.EncloseDBAndTable(db.TemporaryName.L, tableName))
+		return execSQL(replaceIntoSQL)
+	}
+
+	renameSQL := fmt.Sprintf("RENAME TABLE %s TO %s;",
+		utils.EncloseDBAndTable(db.TemporaryName.L, tableName),
+		utils.EncloseDBAndTable(db.Name.L, tableName),
+	)
+	return execSQL(renameSQL)
+}
+
+func (rc *Client) cleanTemporaryDatabase(ctx context.Context, originDB string) {
+	database := utils.TemporaryDBName(originDB)
+	log.Debug("dropping temporary database", zap.Stringer("database", database))
+	sql := fmt.Sprintf("DROP DATABASE IF EXISTS %s", utils.EncloseName(database.L))
+	if err := rc.db.se.Execute(ctx, sql); err != nil {
+		logutil.WarnTerm("failed to drop temporary database, it should be dropped manually",
+			zap.Stringer("database", database),
+			logutil.ShortError(err),
+		)
+	}
+}

pkg/task/common.go

@@ -199,9 +199,9 @@ func DefineTableFlags(command *cobra.Command) {
 }
 
 // DefineFilterFlags defines the --filter and --case-sensitive flags for `full` subcommand.
-func DefineFilterFlags(command *cobra.Command) {
+func DefineFilterFlags(command *cobra.Command, defaultFilter []string) {
 	flags := command.Flags()
-	flags.StringArrayP(flagFilter, "f", []string{"*.*"}, "select tables to process")
+	flags.StringArrayP(flagFilter, "f", defaultFilter, "select tables to process")
 	flags.Bool(flagCaseSensitive, false, "whether the table names used in --filter should be case-sensitive")
 }
 

pkg/task/restore.go

@@ -419,6 +419,10 @@ func RunRestore(c context.Context, g glue.Glue, cmdName string, cfg *RestoreConf
 		return errors.Trace(err)
 	}
 
+	// The cost of rename user table / replace into system table wouldn't be so high.
+	// So leave it out of the pipeline for easier implementation.
+	client.RestoreSystemSchemas(ctx, cfg.TableFilter)
+
 	// Set task summary to success status.
 	summary.SetSuccessStatus(true)
 	return nil

pkg/utils/schema.go

@@ -11,6 +11,7 @@ import (
 	backuppb "github.com/pingcap/kvproto/pkg/backup"
 	"github.com/pingcap/log"
 	"github.com/pingcap/parser/model"
+	"github.com/pingcap/parser/mysql"
 	"github.com/pingcap/tidb/statistics/handle"
 	"github.com/pingcap/tidb/tablecodec"
 
@@ -161,3 +162,14 @@ func EncloseName(name string) string {
 func EncloseDBAndTable(database, table string) string {
 	return fmt.Sprintf("%s.%s", EncloseName(database), EncloseName(table))
 }
+
+// IsSysDB tests whether the database is system DB.
+// Currently, the only system DB is mysql.
+func IsSysDB(dbLowerName string) bool {
+	return dbLowerName == mysql.SystemDB
+}
+
+// TemporaryDBName makes a 'private' database name.
+func TemporaryDBName(db string) model.CIStr {
+	return model.NewCIStr("__TiDB_BR_Temporary_" + db)
+}

tests/br_full_ddl/run.sh

@@ -74,7 +74,7 @@ cluster_index_before_backup=$(run_sql "show variables like '%cluster%';" | awk '
 run_br --pd $PD_ADDR backup full -s "local://$TEST_DIR/$DB" --ratelimit 5 --concurrency 4 --log-file $LOG --ignore-stats=false || cat $LOG
 checksum_count=$(cat $LOG | grep "checksum success" | wc -l | xargs)
 
-if [ "${checksum_count}" != "1" ];then
+if [ "${checksum_count}" -lt "1" ];then
     echo "TEST: [$TEST_NAME] fail on fast checksum"
     echo $(cat $LOG | grep checksum)
     exit 1

tests/br_full_index/run.sh

@@ -44,8 +44,8 @@ BR_LOG_TO_TERM=1
 
 checksum_count=$(cat $LOG | grep "checksum success" | wc -l | xargs)
 
-if [ "${checksum_count}" != "$DB_COUNT" ];then
-    echo "TEST: [$TEST_NAME] fail on fast checksum"
+if [ "${checksum_count}" -lt "$DB_COUNT" ];then
+    echo "TEST: [$TEST_NAME] fail on fast checksum: required $DB_COUNT databases checked, but only ${checksum_count} dbs checked"
     echo $(cat $LOG | grep checksum)
     exit 1
 fi