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| 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):
# 通过反射找rate
if not getattr(self, 'rate', None):
self.rate = self.get_rate() # self.rate = '3/m'
# self.num_requests = 3
# self.duration = 60
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.
"""
# 必须重写 返回谁 用什么做key
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:
# 去配置文件取配置的scope值 '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:
<allowed number of requests>, <period of time in seconds>
"""
if rate is None:
return (None, None)
num, period = rate.split('/') # rate: '3/m' -> '3', 'm'
num_requests = int(num)
duration = {'s': 1, 'm': 60, 'h': 3600, 'd': 86400}[period[0]] # period取字符串索引0 min:m mmmmm:m
return (num_requests, duration) # (3, 60)
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key(IP userID ...)
self.key = self.get_cache_key(request, view)
if self.key is None:
return True
# django缓存
# 1. 导包：from django.core.cache import cache
# 2. 添加缓存：cache.set(key, value, exp)
# 3. 获取缓存： cache.get(key, default_value)
# 初次访问缓存为空 self.history = [] 是存放时间的列表
self.history = self.cache.get(self.key, [])
# 获取当前时间 存到self.now
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.
"""
# 计算下一次访问需要等待的时间
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)
|