avoid deadlock on instances table when running multiple instances

internal/table/table.go

@@ -397,23 +397,16 @@ func (t *Table) Instances(ctx context.Context) (int64, error) {
 // and clears out any inactive instances from the list, such as
 // instances that were unable to call DeleteInstance during shutdown.
 func (t *Table) UpdateInstance(ctx context.Context, id uint32) error {
-	// The MySQL driver doesn't support multiple statements in a single Exec if they contain placeholders.
-	// That's why we use a transaction.
-	tx, err := t.db.BeginTx(ctx, nil)
-	if err != nil {
-		return err
-	}
-	defer tx.Rollback() // nolint: errcheck
 	now := t.Clk.NowUTC()
 	s1 := "INSERT INTO " + t.name + "_instances(id, updated_at) VALUES (" + strconv.FormatUint(uint64(id), 10) + ",IFNULL(CAST(? as DATETIME), UTC_TIMESTAMP())) ON DUPLICATE KEY UPDATE updated_at=IFNULL(?, UTC_TIMESTAMP())"
-	if _, err = tx.ExecContext(ctx, s1, now, now); err != nil {
+	if _, err := t.db.ExecContext(ctx, s1, now, now); err != nil {
 		return err
 	}
 	s2 := "DELETE FROM " + t.name + "_instances WHERE updated_at < IFNULL(CAST(? as DATETIME), UTC_TIMESTAMP) - INTERVAL 1 MINUTE"
-	if _, err = tx.ExecContext(ctx, s2, now); err != nil {
+	if _, err := t.db.ExecContext(ctx, s2, now); err != nil {
 		return err
 	}
-	return tx.Commit()
+	return nil
 }
 
 // DeleteInstance removes an entry from the list of active instances.