export LockName so clients aquiring locks can get their lockname

pkg/dbconn/metadatalock.go

@@ -26,6 +26,7 @@ type MetadataLock struct {
 	closeCh         chan error
 	refreshInterval time.Duration
 	db              *sql.DB
+	lockName        string
 }
 
 func NewMetadataLock(ctx context.Context, dsn string, table *table.TableInfo, logger loggers.Advanced, optionFns ...func(*MetadataLock)) (*MetadataLock, error) {
@@ -51,8 +52,6 @@ func NewMetadataLock(ctx context.Context, dsn string, table *table.TableInfo, lo
 		return nil, err
 	}
 
-	var lockName string
-
 	// Function to acquire the lock
 	getLock := func() error {
 		// https://dev.mysql.com/doc/refman/8.0/en/locking-functions.html#function_get-lock
@@ -63,26 +62,28 @@ func NewMetadataLock(ctx context.Context, dsn string, table *table.TableInfo, lo
 		// The hash is truncated to 8 characters to avoid the maximum lock length.
 		// bizarrely_long_schema_name.thisisareallylongtablenamethisisareallylongtablename60charac ==>
 		// bizarrely_long_schem.thisisareallylongtablenamethisis-66fec116
-		lockName = computeLockName(table)
-		stmt := sqlescape.MustEscapeSQL("SELECT GET_LOCK(%?, %?)", lockName, getLockTimeout.Seconds())
+		mdl.lockName = computeLockName(table)
+		stmt := sqlescape.MustEscapeSQL("SELECT GET_LOCK(%?, %?)", mdl.lockName, getLockTimeout.Seconds())
 		if err := mdl.db.QueryRowContext(ctx, stmt).Scan(&answer); err != nil {
 			return fmt.Errorf("could not acquire metadata lock: %s", err)
 		}
 		if answer == 0 {
 			// 0 means the lock is held by another connection
 			// TODO: we could lookup the connection that holds the lock and report details about it
-			logger.Warnf("could not acquire metadata lock for %s, lock is held by another connection", lockName)
-			return fmt.Errorf("could not acquire metadata lock for %s, lock is held by another connection", lockName)
+			logger.Warnf("could not acquire metadata lock for %s, lock is held by another connection", mdl.lockName)
+
+			// TODO: we could deal in error codes instead of string contains checks.
+			return fmt.Errorf("could not acquire metadata lock for %s, lock is held by another connection", mdl.lockName)
 		} else if answer != 1 {
 			// probably we never get here, but just in case
-			return fmt.Errorf("could not acquire metadata lock %s, GET_LOCK returned: %d", lockName, answer)
+			return fmt.Errorf("could not acquire metadata lock %s, GET_LOCK returned: %d", mdl.lockName, answer)
 		}
 		return nil
 	}
 
 	// Acquire the lock or return an error immediately
 	// We only Infof the initial acquisition.
-	logger.Infof("attempting to acquire metadata lock %s", lockName)
+	logger.Infof("attempting to acquire metadata lock %s", mdl.lockName)
 	if err = getLock(); err != nil {
 		return nil, err
 	}
@@ -98,7 +99,7 @@ func NewMetadataLock(ctx context.Context, dsn string, table *table.TableInfo, lo
 			select {
 			case <-ctx.Done():
 				// Close the dedicated connection to release the lock
-				logger.Warnf("releasing metadata lock for %s", lockName)
+				logger.Warnf("releasing metadata lock for %s", mdl.lockName)
 				mdl.closeCh <- mdl.db.Close()
 				return
 			case <-ticker.C:
@@ -131,7 +132,7 @@ func NewMetadataLock(ctx context.Context, dsn string, table *table.TableInfo, lo
 
 					logger.Infof("re-acquired metadata lock after re-establishing connection: %s.%s", table.SchemaName, table.TableName)
 				} else {
-					logger.Debugf("refreshed metadata lock for %s", lockName)
+					logger.Debugf("refreshed metadata lock for %s", mdl.lockName)
 				}
 			}
 		}
@@ -157,6 +158,10 @@ func (m *MetadataLock) CloseDBConnection(logger loggers.Advanced) error {
 	return nil
 }
 
+func (m *MetadataLock) GetLockName() string {
+	return m.lockName
+}
+
 func computeLockName(table *table.TableInfo) string {
 	schemaNamePart := table.SchemaName
 	if len(schemaNamePart) > 20 {

pkg/migration/runner_test.go

@@ -2769,7 +2769,10 @@ func TestResumeFromCheckpointE2EWithManualSentinel(t *testing.T) {
 			// as tablename while the migration is running.
 			lock, err := dbconn.NewMetadataLock(ctx, testutils.DSN(),
 				&tableInfo, &testLogger{})
-			assert.ErrorContains(t, err, "could not acquire metadata lock for test.resume_checkpoint_e2e_w_sentinel, lock is held by another connection")
+			assert.Error(t, err)
+			if lock != nil {
+				assert.ErrorContains(t, err, fmt.Sprintf("could not acquire metadata lock for %s, lock is held by another connection", lock.GetLockName()))
+			}
 			assert.Nil(t, lock)
 			break
 		}