drf总流程链接

https://www.cnblogs.com/daviddd/p/11918405.html
    

def之节流

'''

承接总流程5.4的限流机制

'''

个人处理

'''
频率限制分为两种，一种是匿名用户，一种是登录用户    匿名用户访问，会将用户的ip作为唯一标识，如果是登录用户，会将用户的用户名或者id作为标识，作为一个字典的键，
    将用户的访问时间作为值存放在一个列表中，字典存放在缓冲中，当用户再次访问时，会将用户的本次的访问时间和列表的最后一个时间元素做差值比较，如果大于自定义的频率时
    间，则删除列表的最后一个时间元素，依次递减，如果差值小于自定义的频率时间，则计算列表的长度,如果小于等于自定义的频率次数，                
    则返回True，可以继续访问，如果大于自定义的频率次数，则返回false，不可继续访问，并提示限制时间

匿名用户由于代理ip的存在，做不到绝对的节流
'''

源码处理机制

'''
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

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
'''

class APIView(View):

    # 限流配置文件
    throttle_classes = api_settings.DEFAULT_THROTTLE_CLASSES
    settings = api_settings
    schema = DefaultSchema()
    
    
    def initial(self, request, *args, **kwargs):
        """
        Runs anything that needs to occur prior to calling the method handler.
        """
        # 5.4，限流机制
        self.check_throttles(request)
        
        
    # 
    def check_throttles(self, request):
        """
        Check if request should be throttled.
        Raises an appropriate exception if the request is throttled.
        """
        throttle_durations = []
        # 5.41实力化限流对象列表，遍历
        for throttle in self.get_throttles():
        
            # 5.43，调用allow_request函数
            if not throttle.allow_request(request, self):
                throttle_durations.append(throttle.wait())

        if throttle_durations:
            # Filter out `None` values which may happen in case of config / rate
            # changes, see #1438
            durations = [
                duration for duration in throttle_durations
                if duration is not None
            ]

            duration = max(durations, default=None)
            self.throttled(request, duration)
            
    # 5.42，执行get_throttles函数，得到限流对象列表
    def get_throttles(self):
        """
        Instantiates and returns the list of throttles that this view uses.
        """
        return [throttle() for throttle in self.throttle_classes]
            
            
            
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_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)


    ## 主逻辑处理
    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
        
        # 处理判断: 可以访问或者抛出异常，执行以下wait方法
        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()
        
        
        

频率限制后的等待时间处理

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)
        
        
        

得到访问者的ip地址或者是登录用户的用户信息：id

class ScopedRateThrottle(SimpleRateThrottle):


    def get_cache_key(self, request, view):
        """
        If `view.throttle_scope` is not set, don't apply this throttle.

        Otherwise generate the unique cache key by concatenating the user id
        with the '.throttle_scope` property of the view.
        """
        if request.user.is_authenticated:
            ident = request.user.pk
        else:
            ident = self.get_ident(request)

        return self.cache_format % {
            'scope': self.scope,
            'ident': ident
        }