def launch():
    """Launch the experiment."""
    try:
        exp = Experiment(db.init_db(drop_all=False))
    except Exception as ex:
        return error_response(
            error_text="Failed to load experiment in /launch: {}".format(str(ex)),
            status=500,
            simple=True,
        )
    try:
        exp.log("Launching experiment...", "-----")
    except IOError as ex:
        return error_response(
            error_text="IOError writing to experiment log: {}".format(str(ex)),
            status=500,
            simple=True,
        )

    try:
        recruitment_details = exp.recruiter.open_recruitment(
            n=exp.initial_recruitment_size
        )
        session.commit()
    except Exception as e:
        return error_response(
            error_text="Failed to open recruitment, check experiment server log "
            "for details: {}".format(str(e)),
            status=500,
            simple=True,
        )

    for task in exp.background_tasks:
        try:
            gevent.spawn(task)
        except Exception:
            return error_response(
                error_text="Failed to spawn task on launch: {}, ".format(task)
                + "check experiment server log for details",
                status=500,
                simple=True,
            )

    if _config().get("replay", False):
        try:
            task = ReplayBackend(exp)
            gevent.spawn(task)
        except Exception:
            return error_response(
                error_text="Failed to launch replay task for experiment."
                "check experiment server log for details",
                status=500,
                simple=True,
            )

    # If the experiment defines a channel, subscribe the experiment to the
    # redis communication channel:
    if exp.channel is not None:
        try:
            from dallinger.experiment_server.sockets import chat_backend

            chat_backend.subscribe(exp, exp.channel)
        except Exception:
            return error_response(
                error_text="Failed to subscribe to chat for channel on launch "
                + "{}".format(exp.channel)
                + ", check experiment server log for details",
                status=500,
                simple=True,
            )

    message = "\n".join(
        (
            "Initial recruitment list:\n{}".format(
                "\n".join(recruitment_details["items"])
            ),
            "Additional details:\n{}".format(recruitment_details["message"]),
        )
    )

    return success_response(recruitment_msg=message)
Launch the experiment.