tracker: get some session variables from downtream (pingcap#1032)

_utils/terror_gen/errors_release.txt

@@ -459,6 +459,7 @@ ErrSchemaTrackerCannotParseDownstreamTable,[code=44008:class=schema-tracker:scop
 ErrSchemaTrackerInvalidCreateTableStmt,[code=44009:class=schema-tracker:scope=internal:level=medium], "Message: %s is not a valid `CREATE TABLE` statement"
 ErrSchemaTrackerRestoreStmtFail,[code=44010:class=schema-tracker:scope=internal:level=medium], "Message: fail to restore the statement"
 ErrSchemaTrackerCannotDropTable,[code=44011:class=schema-tracker:scope=internal:level=high], "Message: failed to drop table for `%s`.`%s` in schema tracker"
+ErrSchemaTrackerInit,[code=44012:class=schema-tracker:scope=internal:level=high], "Message: failed to create schema tracker"
 ErrSchedulerNotStarted,[code=46001:class=scheduler:scope=internal:level=high], "Message: the scheduler has not started"
 ErrSchedulerStarted,[code=46002:class=scheduler:scope=internal:level=medium], "Message: the scheduler has already started"
 ErrSchedulerWorkerExist,[code=46003:class=scheduler:scope=internal:level=medium], "Message: dm-worker with name %s already exists"

dm/config/subtask.go

@@ -81,10 +81,11 @@ func (c *RawDBConfig) SetMaxIdleConns(value int) *RawDBConfig {
 
 // DBConfig is the DB configuration.
 type DBConfig struct {
-	Host             string            `toml:"host" json:"host" yaml:"host"`
-	Port             int               `toml:"port" json:"port" yaml:"port"`
-	User             string            `toml:"user" json:"user" yaml:"user"`
-	Password         string            `toml:"password" json:"-" yaml:"password"` // omit it for privacy
+	Host     string `toml:"host" json:"host" yaml:"host"`
+	Port     int    `toml:"port" json:"port" yaml:"port"`
+	User     string `toml:"user" json:"user" yaml:"user"`
+	Password string `toml:"password" json:"-" yaml:"password"` // omit it for privacy
+	// deprecated, mysql driver could automatically fetch this value
 	MaxAllowedPacket *int              `toml:"max-allowed-packet" json:"max-allowed-packet" yaml:"max-allowed-packet"`
 	Session          map[string]string `toml:"session" json:"session" yaml:"session"`
 
@@ -121,10 +122,6 @@ func (db *DBConfig) Decode(data string) error {
 
 // Adjust adjusts the config.
 func (db *DBConfig) Adjust() {
-	if db.MaxAllowedPacket == nil {
-		cloneV := defaultMaxAllowedPacket
-		db.MaxAllowedPacket = &cloneV
-	}
 }
 
 // SubTaskConfig is the configuration for SubTask

dm/worker/worker.go

@@ -410,6 +410,7 @@ func (w *Worker) handleSubTaskStage(ctx context.Context, stageCh chan ha.Stage,
 		case stage, ok := <-stageCh:
 			if !ok {
 				closed = true
+				break
 			}
 			opType, err := w.operateSubTaskStageWithoutConfig(stage)
 			if err != nil {
@@ -422,6 +423,7 @@ func (w *Worker) handleSubTaskStage(ctx context.Context, stageCh chan ha.Stage,
 		case err, ok := <-errCh:
 			if !ok {
 				closed = true
+				break
 			}
 			// TODO: deal with err
 			log.L().Error("WatchSubTaskStage received an error", zap.Error(err))

errors.toml

@@ -2764,6 +2764,12 @@ description = ""
 workaround = ""
 tags = ["internal", "high"]
 
+[error.DM-schema-tracker-44012]
+message = "failed to create schema tracker"
+description = ""
+workaround = ""
+tags = ["internal", "high"]
+
 [error.DM-scheduler-46001]
 message = "the scheduler has not started"
 description = ""

loader/status.go

@@ -27,7 +27,7 @@ var (
 	printStatusInterval = time.Second * 5
 )
 
-// Status implements SubTaskUnit.Status
+// Status implements Unit.Status
 func (l *Loader) Status() interface{} {
 	finishedSize := l.finishedDataSize.Get()
 	totalSize := l.totalDataSize.Get()
@@ -41,7 +41,7 @@ func (l *Loader) Status() interface{} {
 	return s
 }
 
-// Error implements SubTaskUnit.Error
+// Error implements Unit.Error
 func (l *Loader) Error() interface{} {
 	return &pb.LoadError{}
 }

pkg/conn/basedb.go

@@ -57,8 +57,10 @@ var mockDB sqlmock.Sqlmock
 
 // Apply will build BaseDB with DBConfig
 func (d *DefaultDBProviderImpl) Apply(config config.DBConfig) (*BaseDB, error) {
-	dsn := fmt.Sprintf("%s:%s@tcp(%s:%d)/?charset=utf8mb4&interpolateParams=true&maxAllowedPacket=%d",
-		config.User, config.Password, config.Host, config.Port, *config.MaxAllowedPacket)
+	// maxAllowedPacket=0 can be used to automatically fetch the max_allowed_packet variable from server on every connection.
+	// https://github.com/go-sql-driver/mysql#maxallowedpacket
+	dsn := fmt.Sprintf("%s:%s@tcp(%s:%d)/?charset=utf8mb4&interpolateParams=true&maxAllowedPacket=0",
+		config.User, config.Password, config.Host, config.Port)
 
 	doFuncInClose := func() {}
 	if config.Security != nil && len(config.Security.SSLCA) != 0 &&

pkg/retry/errors.go

@@ -31,6 +31,7 @@ var (
 		"unsupported drop integer primary key",
 		"Unsupported collation",
 		"Invalid default value for",
+		"Unsupported drop primary key",
 	}
 
 	// UnsupportedDMLMsgs list the error messages of some un-recoverable DML, which is used in task auto recovery

pkg/schema/tracker.go

@@ -24,28 +24,67 @@ import (
 	"github.com/pingcap/parser/model"
 	"github.com/pingcap/tidb-tools/pkg/dbutil"
 	"github.com/pingcap/tidb-tools/pkg/filter"
+	tidbConfig "github.com/pingcap/tidb/config"
 	"github.com/pingcap/tidb/domain"
 	"github.com/pingcap/tidb/infoschema"
 	"github.com/pingcap/tidb/kv"
 	"github.com/pingcap/tidb/meta"
 	"github.com/pingcap/tidb/session"
 	"github.com/pingcap/tidb/store/mockstore"
+
+	"github.com/pingcap/dm/pkg/conn"
+	tcontext "github.com/pingcap/dm/pkg/context"
 )
 
 const (
 	waitDDLRetryCount = 10
 	schemaLeaseTime   = 10 * time.Millisecond
 )
 
+var (
+	sessionVars = []string{"sql_mode", "tidb_skip_utf8_check"}
+)
+
 // Tracker is used to track schema locally.
 type Tracker struct {
 	store kv.Storage
 	dom   *domain.Domain
 	se    session.Session
 }
 
-// NewTracker creates a new tracker.
-func NewTracker(sessionCfg map[string]string) (*Tracker, error) {
+// NewTracker creates a new tracker. `sessionCfg` will be set as tracker's session variables if specified, or retrieve
+// some variable from downstream TiDB using `tidbConn`.
+func NewTracker(sessionCfg map[string]string, tidbConn *conn.BaseConn) (*Tracker, error) {
+	// NOTE: tidb uses a **global** config so can't isolate tracker's config from each other. If that isolation is needed,
+	// we might SetGlobalConfig before every call to tracker, or use some patch like https://github.com/bouk/monkey
+	toSet := tidbConfig.NewConfig()
+	toSet.AlterPrimaryKey = true
+	tidbConfig.StoreGlobalConfig(toSet)
+
+	if len(sessionCfg) == 0 {
+		sessionCfg = make(map[string]string)
+		var ignoredColumn interface{}
+		for _, k := range sessionVars {
+			rows, err2 := tidbConn.QuerySQL(tcontext.Background(), fmt.Sprintf("show variables like '%s'", k))
+			if err2 != nil {
+				return nil, err2
+			}
+			if rows.Next() {
+				var value string
+				if err3 := rows.Scan(&ignoredColumn, &value); err3 != nil {
+					return nil, err3
+				}
+				sessionCfg[k] = value
+			}
+			if err2 = rows.Close(); err2 != nil {
+				return nil, err2
+			}
+			if err2 = rows.Err(); err2 != nil {
+				return nil, err2
+			}
+		}
+	}
+
 	store, err := mockstore.NewMockStore(mockstore.WithStoreType(mockstore.MockTiKV))
 	if err != nil {
 		return nil, err

pkg/schema/tracker_test.go

@@ -11,19 +11,22 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-package schema_test
+package schema
 
 import (
 	"context"
+	"database/sql"
 	"encoding/json"
 	"sort"
 	"testing"
 
+	"github.com/DATA-DOG/go-sqlmock"
 	. "github.com/pingcap/check"
-	"github.com/pingcap/dm/pkg/schema"
 	"github.com/pingcap/log"
 	"github.com/pingcap/parser/model"
 	"go.uber.org/zap/zapcore"
+
+	"github.com/pingcap/dm/pkg/conn"
 )
 
 func Test(t *testing.T) {
@@ -32,17 +35,78 @@ func Test(t *testing.T) {
 
 var _ = Suite(&trackerSuite{})
 
-type trackerSuite struct{}
+var (
+	defaultTestSessionCfg = map[string]string{"sql_mode": "ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION"}
+)
+
+type trackerSuite struct {
+	baseConn   *conn.BaseConn
+	db         *sql.DB
+	backupKeys []string
+}
+
+func (s *trackerSuite) SetUpSuite(c *C) {
+	s.backupKeys = sessionVars
+	sessionVars = []string{"sql_mode"}
+	db, _, err := sqlmock.New()
+	s.db = db
+	c.Assert(err, IsNil)
+	con, err := db.Conn(context.Background())
+	c.Assert(err, IsNil)
+	s.baseConn = conn.NewBaseConn(con, nil)
+}
+
+func (s *trackerSuite) TearDownSuite(c *C) {
+	s.db.Close()
+	sessionVars = s.backupKeys
+}
 
-func (s *trackerSuite) TestSessionCfg(c *C) {
+func (s *trackerSuite) TestTiDBAndSessionCfg(c *C) {
 	log.SetLevel(zapcore.ErrorLevel)
 
+	db, mock, err := sqlmock.New()
+	c.Assert(err, IsNil)
+	defer db.Close()
+	con, err := db.Conn(context.Background())
+	c.Assert(err, IsNil)
+	baseConn := conn.NewBaseConn(con, nil)
+
+	// user give correct session config
+	_, err = NewTracker(defaultTestSessionCfg, baseConn)
+	c.Assert(err, IsNil)
+
+	// user give wrong session session, will return error
 	sessionCfg := map[string]string{"sql_mode": "HaHa"}
-	tracker, err := schema.NewTracker(sessionCfg)
+	_, err = NewTracker(sessionCfg, baseConn)
 	c.Assert(err, NotNil)
 
-	tracker, err = schema.NewTracker(nil)
+	// discover session config failed, will return error
+	mock.ExpectQuery("show variables like 'sql_mode'").WillReturnRows(
+		sqlmock.NewRows([]string{"Variable_name", "Value"}).
+			AddRow("sql_mode", "HaHa"))
+	_, err = NewTracker(nil, baseConn)
+	c.Assert(err, NotNil)
+
+	// empty or default config in downstream
+	mock.ExpectQuery("show variables like 'sql_mode'").WillReturnRows(
+		sqlmock.NewRows([]string{"Variable_name", "Value"}).
+			AddRow("sql_mode", ""))
+	tracker, err := NewTracker(nil, baseConn)
+	c.Assert(err, IsNil)
+	c.Assert(mock.ExpectationsWereMet(), IsNil)
+	err = tracker.Exec(context.Background(), "", "create database testdb;")
 	c.Assert(err, IsNil)
+
+	// found session config in downstream
+	mock.ExpectQuery("show variables like 'sql_mode'").WillReturnRows(
+		sqlmock.NewRows([]string{"Variable_name", "Value"}).
+			AddRow("sql_mode", "ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,NO_ZERO_DATE,NO_ZERO_IN_DATE"))
+	tracker, err = NewTracker(nil, baseConn)
+	c.Assert(err, IsNil)
+	c.Assert(mock.ExpectationsWereMet(), IsNil)
+	c.Assert(tracker.se.GetSessionVars().SQLMode.HasOnlyFullGroupBy(), IsTrue)
+	c.Assert(tracker.se.GetSessionVars().SQLMode.HasStrictMode(), IsTrue)
+
 	ctx := context.Background()
 	err = tracker.Exec(ctx, "", "create database testdb;")
 	c.Assert(err, IsNil)
@@ -51,11 +115,12 @@ func (s *trackerSuite) TestSessionCfg(c *C) {
 	err = tracker.Exec(ctx, "testdb", "create table foo (a varchar(255) primary key, b DATETIME NOT NULL DEFAULT '0000-00-00 00:00:00')")
 	c.Assert(err, NotNil)
 
-	// set session config
+	// user set session config, get tracker config from downstream
 	// no `STRICT_TRANS_TABLES`, no error now
 	sessionCfg = map[string]string{"sql_mode": "NO_ZERO_DATE,NO_ZERO_IN_DATE,ANSI_QUOTES"}
-	tracker, err = schema.NewTracker(sessionCfg)
+	tracker, err = NewTracker(sessionCfg, baseConn)
 	c.Assert(err, IsNil)
+	c.Assert(mock.ExpectationsWereMet(), IsNil)
 
 	err = tracker.Exec(ctx, "", "create database testdb;")
 	c.Assert(err, IsNil)
@@ -75,30 +140,34 @@ func (s *trackerSuite) TestSessionCfg(c *C) {
 	cts, err = tracker.GetCreateTable(context.Background(), "testdb", "foo")
 	c.Assert(err, IsNil)
 	c.Assert(cts, Equals, "CREATE TABLE \"foo\" ( \"a\" varchar(255) NOT NULL, PRIMARY KEY (\"a\")) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin")
+
+	// test alter primary key
+	err = tracker.Exec(ctx, "testdb", "alter table \"foo\" drop primary key")
+	c.Assert(err, IsNil)
 }
 
 func (s *trackerSuite) TestDDL(c *C) {
 	log.SetLevel(zapcore.ErrorLevel)
 
-	tracker, err := schema.NewTracker(nil)
+	tracker, err := NewTracker(defaultTestSessionCfg, s.baseConn)
 	c.Assert(err, IsNil)
 
 	// Table shouldn't exist before initialization.
 	_, err = tracker.GetTable("testdb", "foo")
 	c.Assert(err, ErrorMatches, `.*Table 'testdb\.foo' doesn't exist`)
-	c.Assert(schema.IsTableNotExists(err), IsTrue)
+	c.Assert(IsTableNotExists(err), IsTrue)
 
 	_, err = tracker.GetCreateTable(context.Background(), "testdb", "foo")
 	c.Assert(err, ErrorMatches, `.*Table 'testdb\.foo' doesn't exist`)
-	c.Assert(schema.IsTableNotExists(err), IsTrue)
+	c.Assert(IsTableNotExists(err), IsTrue)
 
 	ctx := context.Background()
 	err = tracker.Exec(ctx, "", "create database testdb;")
 	c.Assert(err, IsNil)
 
 	_, err = tracker.GetTable("testdb", "foo")
 	c.Assert(err, ErrorMatches, `.*Table 'testdb\.foo' doesn't exist`)
-	c.Assert(schema.IsTableNotExists(err), IsTrue)
+	c.Assert(IsTableNotExists(err), IsTrue)
 
 	// Now create the table with 3 columns.
 	err = tracker.Exec(ctx, "testdb", "create table foo (a varchar(255) primary key, b varchar(255) as (concat(a, a)), c int)")
@@ -147,7 +216,7 @@ func (s *trackerSuite) TestDDL(c *C) {
 func (s *trackerSuite) TestGetSingleColumnIndices(c *C) {
 	log.SetLevel(zapcore.ErrorLevel)
 
-	tracker, err := schema.NewTracker(nil)
+	tracker, err := NewTracker(defaultTestSessionCfg, s.baseConn)
 	c.Assert(err, IsNil)
 
 	ctx := context.Background()
@@ -186,7 +255,7 @@ func (s *trackerSuite) TestGetSingleColumnIndices(c *C) {
 func (s *trackerSuite) TestCreateSchemaIfNotExists(c *C) {
 	log.SetLevel(zapcore.ErrorLevel)
 
-	tracker, err := schema.NewTracker(nil)
+	tracker, err := NewTracker(defaultTestSessionCfg, s.baseConn)
 	c.Assert(err, IsNil)
 
 	// We cannot create a table without a database.
@@ -214,7 +283,7 @@ func (s *trackerSuite) TestCreateSchemaIfNotExists(c *C) {
 func (s *trackerSuite) TestMultiDrop(c *C) {
 	log.SetLevel(zapcore.ErrorLevel)
 
-	tracker, err := schema.NewTracker(nil)
+	tracker, err := NewTracker(defaultTestSessionCfg, s.baseConn)
 	c.Assert(err, IsNil)
 
 	ctx := context.Background()
@@ -258,7 +327,7 @@ func (aj asJSON) String() string {
 func (s *trackerSuite) TestCreateTableIfNotExists(c *C) {
 	log.SetLevel(zapcore.ErrorLevel)
 
-	tracker, err := schema.NewTracker(nil)
+	tracker, err := NewTracker(defaultTestSessionCfg, s.baseConn)
 	c.Assert(err, IsNil)
 
 	// Create some sort of complicated table.
@@ -322,7 +391,7 @@ func (s *trackerSuite) TestAllSchemas(c *C) {
 	log.SetLevel(zapcore.ErrorLevel)
 	ctx := context.Background()
 
-	tracker, err := schema.NewTracker(nil)
+	tracker, err := NewTracker(defaultTestSessionCfg, s.baseConn)
 	c.Assert(err, IsNil)
 
 	// nothing should exist...