In openerp register the given presence of the current user, and trigger a im_status change if necessary. The status will not be written or sent if not necessary and param user_presence : True, if the user (self._uid) is still detected using its browser.
use this function show below,

@api.model
    def update(self, user_presence=True):

        presence = self.search([('user_id', '=', self._uid)], limit=1)
        # set the default values
        send_notification = True
        values = {
            'last_poll': time.strftime(DEFAULT_SERVER_DATETIME_FORMAT),
            'status': presence and presence.status or 'offline'
        }
        # update the user or a create a new one
        if not presence:  # create a new presence for the user
            values['status'] = 'online'
            values['user_id'] = self._uid
            self.create(values)
        else:  # write the user presence if necessary
            if user_presence:
                values['last_presence'] = time.strftime(DEFAULT_SERVER_DATETIME_FORMAT)
                values['status'] = 'online'
            else:
                threshold = datetime.datetime.now() - datetime.timedelta(seconds=AWAY_TIMER)
                if datetime.datetime.strptime(presence.last_presence, DEFAULT_SERVER_DATETIME_FORMAT) < threshold:
                    values['status'] = 'away'
            send_notification = presence.status != values['status']
            # write only if the last_poll is passed TIMEOUT, or if the status has changed
            delta = datetime.datetime.utcnow() - datetime.datetime.strptime(presence.last_poll, DEFAULT_SERVER_DATETIME_FORMAT)
            if delta > datetime.timedelta(seconds=TIMEOUT) or send_notification:
                # Hide transaction serialization errors, which can be ignored, the presence update is not essential
                with tools.mute_logger('openerp.sql_db'):
                    presence.write(values)
        # avoid TransactionRollbackError
        self.env.cr.commit() # TODO : check if still necessary
        # notify if the status has changed
        if send_notification: # TODO : add user_id to the channel tuple to allow using user_watch in controller presence
            self.env['bus.bus'].sendone((self._cr.dbname, 'bus.presence'), {'id': self._uid, 'im_status': values['status']})
        # gc : disconnect the users having a too old last_poll. 1 on 100 chance to do it.
        if random.random() < 0.01:
            self.check_users_disconnection()
        return True