drf之限流机制

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:
,
"""
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
}

配置文件

REST_FRAMEWORK = {
# 匿名用户与登录用户的节流类
"DEFAULT_THROTTLE_CLASSES": ['rest_framework.throttling.AnonRateThrottle','rest_framework.throttling.UserRateThrottle'],
# 两者分别的频率限制条件设置
"DEFAULT_THROTTLE_RATES": {"anon": '3/m',
"user": '3/m'},