config, sysvar: add config instance.enable_ddl and sysvar `tidb_ena…

…ble_ddl` (pingcap#35425)

ref pingcap#34960

br/cmd/br/BUILD.bazel

@@ -30,7 +30,6 @@ go_library(
         "//br/pkg/utils",
         "//br/pkg/version/build",
         "//config",
-        "//ddl",
         "//parser/model",
         "//session",
         "//util",

br/cmd/br/backup.go

@@ -11,7 +11,7 @@ import (
 	"github.com/pingcap/tidb/br/pkg/trace"
 	"github.com/pingcap/tidb/br/pkg/utils"
 	"github.com/pingcap/tidb/br/pkg/version/build"
-	"github.com/pingcap/tidb/ddl"
+	"github.com/pingcap/tidb/config"
 	"github.com/pingcap/tidb/session"
 	"github.com/spf13/cobra"
 	"go.uber.org/zap"
@@ -78,7 +78,7 @@ func NewBackupCommand() *cobra.Command {
 			task.LogArguments(c)
 
 			// Do not run ddl worker in BR.
-			ddl.RunWorker = false
+			config.GetGlobalConfig().Instance.TiDBEnableDDL.Store(false)
 
 			summary.SetUnit(summary.BackupUnit)
 			return nil

cmd/ddltest/BUILD.bazel

@@ -11,7 +11,7 @@ go_test(
     ],
     flaky = True,
     deps = [
-        "//ddl",
+        "//config",
         "//domain",
         "//kv",
         "//parser/model",

cmd/ddltest/ddl_test.go

@@ -33,7 +33,7 @@ import (
 	_ "github.com/go-sql-driver/mysql"
 	"github.com/pingcap/errors"
 	"github.com/pingcap/log"
-	"github.com/pingcap/tidb/ddl"
+	"github.com/pingcap/tidb/config"
 	"github.com/pingcap/tidb/domain"
 	"github.com/pingcap/tidb/kv"
 	"github.com/pingcap/tidb/parser/model"
@@ -116,7 +116,7 @@ func createDDLSuite(t *testing.T) (s *ddlSuite) {
 	// Stop current DDL worker, so that we can't be the owner now.
 	err = domain.GetDomain(s.ctx).DDL().Stop()
 	require.NoError(t, err)
-	ddl.RunWorker = false
+	config.GetGlobalConfig().Instance.TiDBEnableDDL.Store(false)
 	session.ResetStoreForWithTiKVTest(s.store)
 	s.dom.Close()
 	require.NoError(t, s.store.Close())

config/config.go

@@ -119,6 +119,7 @@ var (
 				"check-mb4-value-in-utf8":       "tidb_check_mb4_value_in_utf8",
 				"enable-collect-execution-info": "tidb_enable_collect_execution_info",
 				"max-server-connections":        "max_connections",
+				"run-ddl":                       "tidb_enable_ddl",
 			},
 		},
 		{
@@ -480,10 +481,11 @@ type Instance struct {
 	ForcePriority         string     `toml:"tidb_force_priority" json:"tidb_force_priority"`
 	MemoryUsageAlarmRatio float64    `toml:"tidb_memory_usage_alarm_ratio" json:"tidb_memory_usage_alarm_ratio"`
 	// EnableCollectExecutionInfo enables the TiDB to collect execution info.
-	EnableCollectExecutionInfo bool   `toml:"tidb_enable_collect_execution_info" json:"tidb_enable_collect_execution_info"`
-	PluginDir                  string `toml:"plugin_dir" json:"plugin_dir"`
-	PluginLoad                 string `toml:"plugin_load" json:"plugin_load"`
-	MaxConnections             uint32 `toml:"max_connections" json:"max_connections"`
+	EnableCollectExecutionInfo bool       `toml:"tidb_enable_collect_execution_info" json:"tidb_enable_collect_execution_info"`
+	PluginDir                  string     `toml:"plugin_dir" json:"plugin_dir"`
+	PluginLoad                 string     `toml:"plugin_load" json:"plugin_load"`
+	MaxConnections             uint32     `toml:"max_connections" json:"max_connections"`
+	TiDBEnableDDL              AtomicBool `toml:"tidb_enable_ddl" json:"tidb_enable_ddl"`
 }
 
 func (l *Log) getDisableTimestamp() bool {
@@ -859,6 +861,7 @@ var defaultConf = Config{
 		PluginDir:                   "/data/deploy/plugin",
 		PluginLoad:                  "",
 		MaxConnections:              0,
+		TiDBEnableDDL:               *NewAtomicBool(true),
 	},
 	Status: Status{
 		ReportStatus:          true,
@@ -1194,7 +1197,7 @@ func (c *Config) Valid() error {
 		}
 		return fmt.Errorf("invalid store=%s, valid storages=%v", c.Store, nameList)
 	}
-	if c.Store == "mocktikv" && !c.RunDDL {
+	if c.Store == "mocktikv" && !c.Instance.TiDBEnableDDL.Load() {
 		return fmt.Errorf("can't disable DDL on mocktikv")
 	}
 	if c.MaxIndexLength < DefMaxIndexLength || c.MaxIndexLength > DefMaxOfMaxIndexLength {

config/config.toml.example

@@ -18,9 +18,6 @@ path = "/tmp/tidb"
 # The socket file to use for connection.
 socket = "/tmp/tidb-{Port}.sock"
 
-# Run ddl worker on this tidb-server.
-run-ddl = true
-
 # Schema lease duration, very dangerous to change only if you know what you do.
 lease = "45s"
 
@@ -462,3 +459,6 @@ tidb_record_plan_in_slow_log = 1
 
 # The maximum permitted number of simultaneous client connections. When the value is 0, the number of connections is unlimited.
 max_connections = 0
+
+# Run ddl worker on this tidb-server.
+tidb_enable_ddl = true

config/config_test.go

@@ -195,9 +195,6 @@ path = "/tmp/tidb"
 # The socket file to use for connection.
 socket = "/tmp/tidb-{Port}.sock"
 
-# Run ddl worker on this tidb-server.
-run-ddl = true
-
 # Schema lease duration, very dangerous to change only if you know what you do.
 lease = "45s"
 
@@ -310,6 +307,9 @@ enable-enum-length-limit = true
 # The maximum permitted number of simultaneous client connections. When the value is 0, the number of connections is unlimited.
 max_connections = 0
 
+# Run ddl worker on this tidb-server.
+tidb_enable_ddl = true
+
 [log]
 # Log level: debug, info, warn, error, fatal.
 level = "info"
@@ -1022,7 +1022,10 @@ func TestConflictInstanceConfig(t *testing.T) {
 	// Just receive a warning and keep their respective values.
 	expectedConflictOptions := map[string]InstanceConfigSection{
 		"": {
-			"", map[string]string{"check-mb4-value-in-utf8": "tidb_check_mb4_value_in_utf8"},
+			"", map[string]string{
+				"check-mb4-value-in-utf8": "tidb_check_mb4_value_in_utf8",
+				"run-ddl":                 "tidb_enable_ddl",
+			},
 		},
 		"log": {
 			"log", map[string]string{"enable-slow-log": "tidb_enable_slow_log"},
@@ -1031,10 +1034,10 @@ func TestConflictInstanceConfig(t *testing.T) {
 			"performance", map[string]string{"force-priority": "tidb_force_priority"},
 		},
 	}
-	_, err = f.WriteString("check-mb4-value-in-utf8 = true \n" +
+	_, err = f.WriteString("check-mb4-value-in-utf8 = true \nrun-ddl = true \n" +
 		"[log] \nenable-slow-log = true \n" +
 		"[performance] \nforce-priority = \"NO_PRIORITY\"\n" +
-		"[instance] \ntidb_check_mb4_value_in_utf8 = false \ntidb_enable_slow_log = false \ntidb_force_priority = \"LOW_PRIORITY\"")
+		"[instance] \ntidb_check_mb4_value_in_utf8 = false \ntidb_enable_slow_log = false \ntidb_force_priority = \"LOW_PRIORITY\"\ntidb_enable_ddl = false")
 	require.NoError(t, err)
 	require.NoError(t, f.Sync())
 	err = conf.Load(configFile)
@@ -1046,6 +1049,8 @@ func TestConflictInstanceConfig(t *testing.T) {
 	require.Equal(t, false, conf.Instance.EnableSlowLog.Load())
 	require.Equal(t, "NO_PRIORITY", conf.Performance.ForcePriority)
 	require.Equal(t, "LOW_PRIORITY", conf.Instance.ForcePriority)
+	require.Equal(t, true, conf.RunDDL)
+	require.Equal(t, false, conf.Instance.TiDBEnableDDL.Load())
 	require.Equal(t, 0, len(DeprecatedOptions))
 	for _, conflictOption := range ConflictOptions {
 		expectedConflictOption, ok := expectedConflictOptions[conflictOption.SectionName]
@@ -1075,6 +1080,7 @@ func TestDeprecatedConfig(t *testing.T) {
 		"": {
 			"", map[string]string{
 				"enable-collect-execution-info": "tidb_enable_collect_execution_info",
+				"run-ddl":                       "tidb_enable_ddl",
 			},
 		},
 		"log": {
@@ -1090,7 +1096,7 @@ func TestDeprecatedConfig(t *testing.T) {
 			},
 		},
 	}
-	_, err = f.WriteString("enable-collect-execution-info = false \n" +
+	_, err = f.WriteString("enable-collect-execution-info = false \nrun-ddl = false \n" +
 		"[plugin] \ndir=\"/plugin-path\" \nload=\"audit-1,whitelist-1\" \n" +
 		"[log] \nslow-threshold = 100 \n" +
 		"[performance] \nmemory-usage-alarm-ratio = 0.5")

ddl/ddl.go

@@ -37,6 +37,7 @@ import (
 	"github.com/pingcap/kvproto/pkg/kvrpcpb"
 	"github.com/pingcap/tidb/config"
 	"github.com/pingcap/tidb/ddl/util"
+	"github.com/pingcap/tidb/domain/infosync"
 	"github.com/pingcap/tidb/infoschema"
 	"github.com/pingcap/tidb/kv"
 	"github.com/pingcap/tidb/meta"
@@ -565,6 +566,9 @@ func newDDL(ctx context.Context, options ...Option) *ddl {
 		ddlJobCh:          make(chan struct{}, 100),
 	}
 
+	// Register functions for enable/disable ddl when changing system variable `tidb_enable_ddl`.
+	variable.EnableDDL = d.EnableDDL
+	variable.DisableDDL = d.DisableDDL
 	variable.SwitchConcurrentDDL = d.SwitchConcurrentDDL
 
 	return d
@@ -638,37 +642,36 @@ func (d *ddl) prepareWorkers4legacyDDL() {
 
 // Start implements DDL.Start interface.
 func (d *ddl) Start(ctxPool *pools.ResourcePool) error {
-	logutil.BgLogger().Info("[ddl] start DDL", zap.String("ID", d.uuid), zap.Bool("runWorker", RunWorker))
+	logutil.BgLogger().Info("[ddl] start DDL", zap.String("ID", d.uuid), zap.Bool("runWorker", config.GetGlobalConfig().Instance.TiDBEnableDDL.Load()))
 
 	d.wg.Run(d.limitDDLJobs)
 	d.sessPool = newSessionPool(ctxPool, d.store)
-	// If RunWorker is true, we need campaign owner and do DDL job.
-	// Otherwise, we needn't do that.
-	if RunWorker {
-		d.ownerManager.SetBeOwnerHook(func() {
-			var err error
-			d.ddlSeqNumMu.seqNum, err = d.GetNextDDLSeqNum()
-			if err != nil {
-				logutil.BgLogger().Error("error when getting the ddl history count", zap.Error(err))
-			}
-		})
-
-		err := d.ownerManager.CampaignOwner()
+	d.ownerManager.SetBeOwnerHook(func() {
+		var err error
+		d.ddlSeqNumMu.seqNum, err = d.GetNextDDLSeqNum()
 		if err != nil {
-			return errors.Trace(err)
+			logutil.BgLogger().Error("error when getting the ddl history count", zap.Error(err))
 		}
+	})
+
+	d.delRangeMgr = d.newDeleteRangeManager(ctxPool == nil)
 
-		d.delRangeMgr = d.newDeleteRangeManager(ctxPool == nil)
+	d.prepareWorkers4ConcurrencyDDL()
+	d.prepareWorkers4legacyDDL()
 
-		d.prepareWorkers4ConcurrencyDDL()
-		d.prepareWorkers4legacyDDL()
+	go d.schemaSyncer.StartCleanWork()
+	if config.TableLockEnabled() {
+		d.wg.Add(1)
+		go d.startCleanDeadTableLock()
+	}
+	metrics.DDLCounter.WithLabelValues(metrics.StartCleanWork).Inc()
 
-		go d.schemaSyncer.StartCleanWork()
-		if config.TableLockEnabled() {
-			d.wg.Add(1)
-			go d.startCleanDeadTableLock()
+	// If tidb_enable_ddl is true, we need campaign owner and do DDL job.
+	// Otherwise, we needn't do that.
+	if config.GetGlobalConfig().Instance.TiDBEnableDDL.Load() {
+		if err := d.EnableDDL(); err != nil {
+			return err
 		}
-		metrics.DDLCounter.WithLabelValues(metrics.StartCleanWork).Inc()
 	}
 
 	variable.RegisterStatistics(d)
@@ -681,6 +684,35 @@ func (d *ddl) Start(ctxPool *pools.ResourcePool) error {
 	return nil
 }
 
+// EnableDDL enable this node to execute ddl.
+// Since ownerManager.CampaignOwner will start a new goroutine to run ownerManager.campaignLoop,
+// we should make sure that before invoking EnableDDL(), ddl is DISABLE.
+func (d *ddl) EnableDDL() error {
+	err := d.ownerManager.CampaignOwner()
+	return errors.Trace(err)
+}
+
+// DisableDDL disable this node to execute ddl.
+// We should make sure that before invoking DisableDDL(), ddl is ENABLE.
+func (d *ddl) DisableDDL() error {
+	if d.ownerManager.IsOwner() {
+		// If there is only one node, we should NOT disable ddl.
+		serverInfo, err := infosync.GetAllServerInfo(d.ctx)
+		if err != nil {
+			logutil.BgLogger().Error("[ddl] error when GetAllServerInfo", zap.Error(err))
+			return err
+		}
+		if len(serverInfo) <= 1 {
+			return dbterror.ErrDDLSetting.GenWithStackByArgs("can not disable ddl when there is only one instance")
+		}
+		// FIXME: if possible, when this node is the only node with DDL, ths setting of DisableDDL should fail.
+	}
+
+	// disable campaign by interrupting campaignLoop
+	d.ownerManager.CampaignCancel()
+	return nil
+}
+
 // GetNextDDLSeqNum return the next DDL seq num.
 func (d *ddl) GetNextDDLSeqNum() (uint64, error) {
 	var count uint64
@@ -830,7 +862,7 @@ func getJobCheckInterval(job *model.Job, i int) (time.Duration, bool) {
 
 func (d *ddl) asyncNotifyWorker(job *model.Job) {
 	// If the workers don't run, we needn't notify workers.
-	if !RunWorker {
+	if !config.GetGlobalConfig().Instance.TiDBEnableDDL.Load() {
 		return
 	}
 	if variable.EnableConcurrentDDL.Load() {

ddl/ddl_worker.go

@@ -50,8 +50,6 @@ import (
 )
 
 var (
-	// RunWorker indicates if this TiDB server starts DDL worker and can run DDL job.
-	RunWorker = true
 	// ddlWorkerID is used for generating the next DDL worker ID.
 	ddlWorkerID = atomicutil.NewInt32(0)
 	// WaitTimeWhenErrorOccurred is waiting interval when processing DDL jobs encounter errors.

errno/errcode.go

@@ -1073,6 +1073,8 @@ const (
 	ErrHTTPServiceError                   = 8243
 	ErrPartitionColumnStatsMissing        = 8244
 	ErrColumnInChange                     = 8245
+	ErrDDLSetting                         = 8246
+
 	// TiKV/PD/TiFlash errors.
 	ErrPDServerTimeout           = 9001
 	ErrTiKVServerTimeout         = 9002

errno/errname.go

@@ -1066,6 +1066,7 @@ var MySQLErrName = map[uint16]*mysql.ErrMessage{
 	ErrJSONObjectKeyTooLong:        mysql.Message("TiDB does not yet support JSON objects with the key length >= 65536", nil),
 	ErrPartitionStatsMissing:       mysql.Message("Build table: %s global-level stats failed due to missing partition-level stats", nil),
 	ErrPartitionColumnStatsMissing: mysql.Message("Build table: %s global-level stats failed due to missing partition-level column stats, please run analyze table to refresh columns of all partitions", nil),
+	ErrDDLSetting:                  mysql.Message("Error happened when enable/disable DDL: %s", nil),
 	ErrNotSupportedWithSem:         mysql.Message("Feature '%s' is not supported when security enhanced mode is enabled", nil),
 
 	ErrPlacementPolicyCheck:            mysql.Message("Placement policy didn't meet the constraint, reason: %s", nil),

errors.toml

@@ -1261,6 +1261,11 @@ error = '''
 column %s id %d does not exist, this column may have been updated by other DDL ran in parallel
 '''
 
+["ddl:8246"]
+error = '''
+Error happened when enable/disable DDL: %s
+'''
+
 ["domain:8027"]
 error = '''
 Information schema is out of date: schema failed to update in 1 lease, please make sure TiDB can connect to TiKV