Django의 DRF 소스 분석(4) - 주파수 인증 구성 요소

    def check_throttles(self, request):
        """
        Check if request should be throttled.
        Raises an appropriate exception if the request is throttled.
        """
        for throttle in self.get_throttles():
            if not throttle.allow_request(request, self):
                self.throttled(request, throttle.wait())

class SimpleRateThrottle(BaseThrottle):
    cache = default_cache
    timer = time.time
    cache_format = 'throttle_%(scope)s_%(ident)s'
    scope = None
    THROTTLE_RATES = api_settings.DEFAULT_THROTTLE_RATES

    def __init__(self):
        if not getattr(self, 'rate', None):
            self.rate = self.get_rate()
        self.num_requests, self.duration = self.parse_rate(self.rate)

    def get_cache_key(self, request, view):
        #                       ，        ip，      
        """
        Should return a unique cache-key which can be used for throttling.
        Must be overridden.

        May return `None` if the request should not be throttled.
        """
        raise NotImplementedError('.get_cache_key() must be overridden')

    def get_rate(self):
        """
        Determine the string representation of the allowed request rate.
                         
        """
        #    SimpleRateThrottle          scope ，    ，    ，       if
        if not getattr(self, 'scope', None):
            msg = ("You must set either `.scope` or `.rate` for '%s' throttle" %
                   self.__class__.__name__)
            raise ImproperlyConfigured(msg)

        try:
            #       scope   settings.py    REST_FRAMEWORK     DEFAULT_THROTTLE_RATES              "qzk":"3/m"
            return self.THROTTLE_RATES[self.scope]
        except KeyError:
            msg = "No default throttle rate set for '%s' scope" % self.scope
            raise ImproperlyConfigured(msg)

    def parse_rate(self, rate):
        """
        Given the request rate string, return a two tuple of:
        , 
        """
        if rate is None:
            return (None, None)
        #   "/"    ，      num,period
        num, period = rate.split('/')
        #  num          
        num_requests = int(num)
        #    period =     “m”   “minute”
        # duration                   {...}["m"]
        # period[0]               （  0）
        duration = {'s': 1, 'm': 60, 'h': 3600, 'd': 86400}[period[0]]
        #       num_reuqets=3   duration=60
        return (num_requests, duration)

    def allow_request(self, request, view):
        """
        Implement the check to see if the request should be throttled.

        On success calls `throttle_success`.
                throttle_success
        On failure calls `throttle_failure`.
                `throttle_failure`
        """
        if self.rate is None:
            return True
        #    self.key             ip（     ），                 ，                    key
        self.key = self.get_cache_key(request, view)
        #       ip    none
        if self.key is None:
            return True
        #   ip    self.cache     value---> [ctime2,ctime1]
        self.history = self.cache.get(self.key, [])  # self.history              
        #       
        self.now = self.timer()

        # Drop any requests from the history which have now passed the
        # throttle duration
        #                （  ）          <=     -        （60）
        while self.history and self.history[-1] <= self.now - self.duration:
            self.history.pop()  #            pop    （  ）
        if len(self.history) >= self.num_requests:  #         >=       （3）
            return self.throttle_failure()   #    False
        return self.throttle_success()  #   True

    def throttle_success(self):
        """
        Inserts the current request's timestamp along with the key
        into the cache.
        """
        self.history.insert(0, self.now)  #                 
        self.cache.set(self.key, self.history, self.duration)  # 
        return True

    def throttle_failure(self):
        """
        Called when a request to the API has failed due to throttling.
        """
        return False

    def wait(self):
        """
        Returns the recommended next request time in seconds.
        """
        if self.history:
            remaining_duration = self.duration - (self.now - self.history[-1])
        else:
            remaining_duration = self.duration

        available_requests = self.num_requests - len(self.history) + 1
        if available_requests <= 0:
            return None

        return remaining_duration / float(available_requests)

class BaseThrottle(object):
    """
    Rate throttling of requests.
    """

    def allow_request(self, request, view):
        """
        Return `True` if the request should be allowed, `False` otherwise.
        """
        raise NotImplementedError('.allow_request() must be overridden')

    def get_ident(self, request):
        """
        Identify the machine making the request by parsing HTTP_X_FORWARDED_FOR
        if present and number of proxies is > 0. If not use all of
        HTTP_X_FORWARDED_FOR if it is available, if not use REMOTE_ADDR.
        """
        #            
        xff = request.META.get('HTTP_X_FORWARDED_FOR')
        #    ip  
        remote_addr = request.META.get('REMOTE_ADDR')
        num_proxies = api_settings.NUM_PROXIES

        if num_proxies is not None:
            if num_proxies == 0 or xff is None:
                return remote_addr
            addrs = xff.split(',')
            client_addr = addrs[-min(num_proxies, len(addrs))]
            return client_addr.strip()

        return ''.join(xff.split()) if xff else remote_addr

    def wait(self):
        """
        Optionally, return a recommended number of seconds to wait before
        the next request.
        """
        return None

"""          """
'''
              （  SimpleRateThrottle） --->         scope  --->    get_cache_key       self.get_ident(request)---->               
    
    
        ：
        1.APIView
        2.---->dispatch
        3.---->self.initial(request, *args, **kwargs)
        4.---->self.check_throttles(request)
        5.---->throttle.allow_request(request, self)
        6.---->self.get_cache_key(request, view)(     )（    ip）
        7.---->self.cache.get(self.key, [])   ip    ip      
        8.---->      （self.rate，self.num_requests，self.duration）                （__init__）：
                8.1--> self.rate = self.get_rate()-->self.THROTTLE_RATES[self.scope]
                    -->api_settings.DEFAULT_THROTTLE_RATES(      )
                       self.rate  --->        'qzk':'3/m'
                8.2-->self.num_requests, self.duration = self.parse_rate(self.rate)
                       self.num_requests           （3）
                        self.duration          （60）
        9.---->       ，         ，   
                True：——>   throttle_success：
                            self.history.insert(0, self.now)  #               
                            #    key,history,duration   {}    
                            self.cache.set(self.key, self.history, self.duration)
                False ：--->    throttle_failure ，   Ture
'''