def heartbeat_callback(self, session=None):
        """"""

        if self.terminating:
            # ensure termination if processes are created later
            self.task_runner.terminate()
            return

        self.task_instance.refresh_from_db()
        ti = self.task_instance

        fqdn = get_hostname()
        same_hostname = fqdn == ti.hostname
        same_process = ti.pid == os.getpid()

        if ti.state == State.RUNNING:
            if not same_hostname:
                self.log.warning("The recorded hostname %s "
                                 "does not match this instance's hostname "
                                 "%s", ti.hostname, fqdn)
                raise AirflowException("Hostname of job runner does not match")
            elif not same_process:
                current_pid = os.getpid()
                self.log.warning("Recorded pid %s does not match "
                                 "the current pid %s", ti.pid, current_pid)
                raise AirflowException("PID of job runner does not match")
        elif (
                self.task_runner.return_code() is None and
                hasattr(self.task_runner, 'process')
        ):
            self.log.warning(
                "State of this instance has been externally set to %s. "
                "Taking the poison pill.",
                ti.state
            )
            self.task_runner.terminate()
            self.terminating = True