        """Start a new database transaction with the given connection.

        Note: The given func may be called multiple times under certain
        failure modes. This is normally fine when in a standard transaction,
        but care must be taken if the connection is in `autocommit` mode that
        the function will correctly handle being aborted and retried half way
        through its execution.
…
        try:
            MAX_NUMBER_OF_ATTEMPTS = 5
            for attempt_number in range(1, MAX_NUMBER_OF_ATTEMPTS + 1):
…
                try:
…
                        r = func(cursor, *args, **kwargs)
                        opentracing.log_kv({"message": "commit"})
                        conn.commit()
                        return r
…
                except self.engine.module.DatabaseError as e:
                    if self.engine.is_deadlock(e):
                        transaction_logger.warning(
                            "[TXN DEADLOCK] {%s} %d/%d",
                            name,
                            attempt_number,
                            MAX_NUMBER_OF_ATTEMPTS,
                        )
                        try:
                            with opentracing.start_active_span("db.rollback"):
                                conn.rollback()
                        except self.engine.module.Error as e1:
                            transaction_logger.warning(
                                "[TXN EROLL] {%s} %s",
                                name,
                                e1,
                            )
                        # Keep retrying if we haven't reached max attempts
                        if attempt_number < MAX_NUMBER_OF_ATTEMPTS:
                            continue
                    raise

Échauffement