drf 节流/频率控制

Posted 2020-11-28 yzm1017

目录

• 节流/频率控制
  • 简单使用：
  • 源码：
  • 流程分析：

节流/频率控制

节流类似于权限，它确定是否应授权请求。节流指示临时状态，并用于控制客户端可以向API发出的请求的频率 。在drf认证、权限之后执行。

原理思路：

{
    throttle_anon_1.1.1.1:[100121340,], 
}

限制：60s能访问3次
来访问时：
    1.获取当前时间 100121280
    2.100121280-60 = 100121220，小于100121220所有记录删除
    3.判断1分钟以内已经访问多少次了？ 4 
    4.无法访问
停一会
来访问时：
    1.获取当前时间 100121340
    2.100121340-60 = 100121280,小于100121280所有记录删除
    3.判断1分钟以内已经访问多少次了？ 0
    4.可以访问

简单使用：

配置：

REST_FRAMEWORK = {
    # 节流配置
    "DEFAULT_THROTTLE_RATES": {
        "anon": '10/m'},    # 每分钟只能访问10次

}

视图：设置某个视图的访问频率，需要设置throttle_classes = [AnonRateThrottle,]列表

from rest_framework.views import APIView
from rest_framework.response import Response

from rest_framework.throttling import AnonRateThrottle,BaseThrottle

class ArticleView(APIView):
    throttle_classes = [AnonRateThrottle,]
    def get(self,request,*args,**kwargs):
        return Response('文章列表')

class ArticleDetailView(APIView):
    def get(self,request,*args,**kwargs):
        return Response('文章列表')

源码：

请求到来是，执行APIView类的dispatch方法，然后执行initial方法,最后执行check_throttles方法。

    def initial(self, request, *args, **kwargs):
        """
        Runs anything that needs to occur prior to calling the method handler.
        """
        self.format_kwarg = self.get_format_suffix(**kwargs)

        # Perform content negotiation and store the accepted info on the request
        neg = self.perform_content_negotiation(request)
        request.accepted_renderer, request.accepted_media_type = neg

        # Determine the API version, if versioning is in use.
        version, scheme = self.determine_version(request, *args, **kwargs)
        request.version, request.versioning_scheme = version, scheme

        # Ensure that the incoming request is permitted
        self.perform_authentication(request)
        self.check_permissions(request)
        self.check_throttles(request)   # 节流限制

先获取节流类对象列表，然后循环执行每个对象的allow_request方法，AnonRateThrottle类没有，找它父类。

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

    return [throttle() for throttle in self.throttle_classes]

执行SimpleRateThrottle类的allow_request方法，获取用户标识，并进行判断。

class BaseThrottle:
    """
    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')
        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


class SimpleRateThrottle(BaseThrottle):
    """
    A simple cache implementation, that only requires `.get_cache_key()`
    to be overridden.

    The rate (requests / seconds) is set by a `rate` attribute on the View
    class.  The attribute is a string of the form 'number_of_requests/period'.

    Period should be one of: ('s', 'sec', 'm', 'min', 'h', 'hour', 'd', 'day')

    Previous request information used for throttling is stored in the cache.
    """
    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):
        """
        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.
        """
        if not getattr(self, 'scope', None):
            msg = ("You must set either `.scope` or `.rate` for '%s' throttle" %
                   self.__class__.__name__)
            raise ImproperlyConfigured(msg)

        try:
            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:
        <allowed number of requests>, <period of time in seconds>
        """
        if rate is None:
            return (None, None)
        num, period = rate.split('/')
        num_requests = int(num)
        duration = {'s': 1, 'm': 60, 'h': 3600, 'd': 86400}[period[0]]
        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`.
        On failure calls `throttle_failure`.
        """
        if self.rate is None:
            return True

        # 获取请求用户的IP
        self.key = self.get_cache_key(request, view)
        if self.key is None:
            return True

        # 根据IP获取他的所有访问记录，[]
        self.history = self.cache.get(self.key, [])

        self.now = self.timer()

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

    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 AnonRateThrottle(SimpleRateThrottle):
    """
    Limits the rate of API calls that may be made by a anonymous users.

    The IP address of the request will be used as the unique cache key.
    """
    scope = 'anon'

    def get_cache_key(self, request, view):
        if request.user.is_authenticated:
            return None  # Only throttle unauthenticated requests.

        return self.cache_format % {
            'scope': self.scope,
            'ident': self.get_ident(request)
        }


分析：   
    1.self.key获取当前请求用户的IP(标识)，再使用self.history根据用户的标识获取其访问的列表记录， 
    2.然后通过当前的时间 - 设定的时间 后循环与列表的最后对比，将不在该时间端的记录 pop
    3.len列表，如果获取到的数值大于等于限定的次数，则返回False，不让其访问。否则，允许访问，并在列表索引0位置上添加记录。

流程分析：

    1.SimpleRateThrottle类执行__init__方法，可以在其中设置访问的频率，get_rate() 获取配置文件中设置的值， parse_rate() 能够对值进行解析， 先分割，再返回一个元组。
    2.请求到来后，执行APIView类的dispath方法，通过initial获取节流类对象列表[AnonRateThrottle,]，循环列表
    2.执行每个对象的allow_request(), 找到父类，self.key 获取请求的IP，然后进行拼接 throttle_anon_IP地址
    3.self.history 获取当前用户记录列表
    4.进行判断，self.history[-1] <= self.now - self.duration
    len(self.history) >= self.num_requests
    
    返回 TrueFalse,表示是否可以访问。