頻率組件

一：自定義頻率類

仿源碼自定義頻率規則：

class MyThrottles():
    VISIT_RECORD = {}
    def __init__(self):
        self.history=None
    def allow_request(self,request, view):
        #（1）取出訪問者ip
        ip=request.META.get('REMOTE_ADDR')
        import time
        ctime=time.time()
        # （2）判斷當前ip不在訪問字典裏，添加進去，而且直接返回True,表示第一次訪問
        if ip not in self.VISIT_RECORD:
            self.VISIT_RECORD[ip]=[ctime,]
            return True
        self.history=self.VISIT_RECORD.get(ip)
        # （3）循環判斷當前ip的列表，有值，而且當前時間減去列表的最後一個時間大於60s，把這種數據pop掉，這樣列表中只有60s之內的訪問時間，
        while self.history and ctime-self.history[-1]>60:
            self.history.pop()
        # （4）判斷，當列表小於3，說明一分鐘之內訪問不足三次，把當前時間插入到列表第一個位置，返回True，順利經過
        # （5）當大於等於3，說明一分鐘內訪問超過三次，返回False驗證失敗
        if len(self.history)<3:
            self.history.insert(0,ctime)
            return True
        else:
            return False
    def wait(self):
        import time
        ctime=time.time()
        return 60-(ctime-self.history[-1])

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二：內置頻率類的使用

定義頻率類，必須繼承SimpleRateThrottle類：

from rest_framework.throttling import SimpleRateThrottle
class VisitThrottle(SimpleRateThrottle):
    # 必須配置scope參數 經過scope參數去settings中找頻率限定的規則
    scope = 'throttle'
    # 必須定義 get_cache_key函數 返回用戶標識的key  這裏借用源碼中BaseThrottle類（SimpleRateThrottle的父類）中的get_ident函數返回用戶ip地址
    def get_cache_key(self, request, view):
        return self.get_ident(request)

局部使用：

視圖函數中加上
throttle_classes = [VisitThrottle,]

全局使用：settings中配置

REST_FRAMEWORK={
    'DEFAULT_THROTTLE_CLASSES':['utils.common.VisitThrottle'],
    # 局部使用也要在settings中配置上 DEFAULT_THROTTLE_RATES 經過self.scope取頻率規則 （一分鐘訪問3次）
    'DEFAULT_THROTTLE_RATES':{'throttle':'3/m',}
}

設置錯誤信息爲中文：

class Course(APIView):
    authentication_classes = [TokenAuth, ]
    permission_classes = [UserPermission, ]
    throttle_classes = [MyThrottles,]

    def get(self, request):
        return HttpResponse('get')

    def post(self, request):
        return HttpResponse('post')

    # 函數名爲throttled 重寫Throttled類中默認的錯誤信息
    def throttled(self, request, wait):
        from rest_framework.exceptions import Throttled
        class MyThrottled(Throttled):
            default_detail = '訪問頻繁'
            extra_detail_singular = '等待 {wait} second.'
            extra_detail_plural = '等待 {wait} seconds.'
        raise MyThrottled(wait)

 

三：源碼分析

源碼查看流程：

APIView的dispatch方法()  ---- self.initial(request, *args, **kwargs) ---  self.check_throttles(request)

 

SimpleRateThrottle類詳解：

class SimpleRateThrottle(BaseThrottle):
    # 字典 {ip1:[time1,time2],ip2:[time1,time2]} 放在緩存中
    cache = default_cache
    # 獲取當前時間
    timer = time.time
    # 作了一個字符串格式化，爲登陸用戶ip限制，配合auth模塊使用
    cache_format = 'throttle_%(scope)s_%(ident)s'
    scope = None
    # 從配置文件中取DEFAULT_THROTTLE_RATES
    THROTTLE_RATES = api_settings.DEFAULT_THROTTLE_RATES

    def __init__(self):
        if not getattr(self, 'rate', None):
            # 從配置文件中找出scope配置的名字對應的值
            self.rate = self.get_rate()
        self.num_requests, self.duration = self.parse_rate(self.rate)
    # 這個方法須要重寫，不然直接拋異常
    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):
        if not getattr(self, 'scope', None):
            msg = ("You must set either `.scope` or `.rate` for '%s' throttle" %
                   self.__class__.__name__)
            raise ImproperlyConfigured(msg)

        try:
            # 獲取在setting裏配置的字典中的值
            return self.THROTTLE_RATES[self.scope]
        except KeyError:
            msg = "No default throttle rate set for '%s' scope" % self.scope
            raise ImproperlyConfigured(msg)
    # 解析 3/m這種傳參
    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)
        # 只取了第一位，也就是 3/mimmmmmmm也是表明一分鐘
        duration = {'s': 1, 'm': 60, 'h': 3600, 'd': 86400}[period[0]]
        return (num_requests, duration)
    # 頻率驗證邏輯
    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

        self.key = self.get_cache_key(request, view)
        if self.key is None:
            return True

        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()
    # 成功返回true，而且插入到緩存中
    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
    # 失敗返回false
    def throttle_failure(self):
        """
        Called when a request to the API has failed due to throttling.
        """
        return False
    # 計算返回還需等待多長時間
    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)

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