Adds data necessary for Horizon to function to the request.

def _process_request(self, request):
        """Adds data necessary for Horizon to function to the request."""

        request.horizon = {'dashboard': None,
                           'panel': None,
                           'async_messages': []}
        if not hasattr(request, "user") or not request.user.is_authenticated:
            # proceed no further if the current request is already known
            # not to be authenticated
            # it is CRITICAL to perform this check as early as possible
            # to avoid creating too many sessions
            return None

        # Since we know the user is present and authenticated, lets refresh the
        # session expiry if configured to do so.
        if getattr(settings, "SESSION_REFRESH", True):
            timeout = getattr(settings, "SESSION_TIMEOUT", 3600)
            token_life = request.user.token.expires - datetime.datetime.now(
                pytz.utc)
            session_time = min(timeout, int(token_life.total_seconds()))
            request.session.set_expiry(session_time)

        if request.is_ajax():
            # if the request is Ajax we do not want to proceed, as clients can
            #  1) create pages with constant polling, which can create race
            #     conditions when a page navigation occurs
            #  2) might leave a user seemingly left logged in forever
            #  3) thrashes db backed session engines with tons of changes
            return None
        # If we use cookie-based sessions, check that the cookie size does not
        # reach the max size accepted by common web browsers.
        if (
            settings.SESSION_ENGINE ==
            'django.contrib.sessions.backends.signed_cookies'
        ):
            max_cookie_size = getattr(
                settings, 'SESSION_COOKIE_MAX_SIZE', None)
            session_cookie_name = getattr(
                settings, 'SESSION_COOKIE_NAME', None)
            session_key = request.COOKIES.get(session_cookie_name)
            if max_cookie_size is not None and session_key is not None:
                cookie_size = sum((
                    len(key) + len(value)
                    for key, value in request.COOKIES.items()
                ))
                if cookie_size >= max_cookie_size:
                    LOG.error(
                        'Total Cookie size for user_id: %(user_id)s is '
                        '%(cookie_size)sB >= %(max_cookie_size)sB. '
                        'You need to configure file-based or database-backed '
                        'sessions instead of cookie-based sessions: '
                        'https://docs.openstack.org/horizon/latest/'
                        'admin/sessions.html',
                        {
                            'user_id': request.session.get(
                                'user_id', 'Unknown'),
                            'cookie_size': cookie_size,
                            'max_cookie_size': max_cookie_size,
                        }
                    )

        tz = utils.get_timezone(request)
        if tz:
            timezone.activate(tz)