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。