限流组件的基本使用及源码剖析
使用方法有自己编写类和继承DRF的类
class BaseThrottle:
def allow_request(self, request, view):
raise NotImplementedError('.allow_request() must be overridden')
def get_ident(self, request):
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):
return None
继承后编写类
后面将在继承SimpleRateThrottle的基础上编写自定义的限流类：
class SimpleRateThrottle(BaseThrottle):
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):
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:
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):
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):
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()
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):
self.history.insert(0, self.now)
self.cache.set(self.key, self.history, self.duration)
return True
def throttle_failure(self):
return False
def wait(self):
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)
编写自己的限流类：
class MyThrottle(SimpleRateThrottle):
def get_cache_key(self, request, view):
scope = 'xxx'
THROTTLE_RATES = {'xxx':'5/m'}
if request.user:
ident = request.user.id
else:
ident = self.get_ident(request)
return self.cache_format % {'scope':self.scope, 'ident':ident}
限流类的使用
class login(APIView):
throttle_classes = [MyThrottle,]
def post(self,request,*args,**kwargs):
return
限流组件源码剖析
接收到请求后，从dispatch调用self.initial
def dispatch(self, request, *args, **kwargs):
"""
`.dispatch()` is pretty much the same as Django's regular dispatch,
but with extra hooks for startup, finalize, and exception handling.
"""
self.args = args
self.kwargs = kwargs
request = self.initialize_request(request, *args, **kwargs)
self.request = request
self.headers = self.default_response_headers # deprecate?
try:
self.initial(request, *args, **kwargs)
# Get the appropriate handler method
if request.method.lower() in self.http_method_names:
handler = getattr(self, request.method.lower(),
self.http_method_not_allowed)
else:
handler = self.http_method_not_allowed
response = handler(request, *args, **kwargs)
except Exception as exc:
response = self.handle_exception(exc)
self.response = self.finalize_response(request, response, *args, **kwargs)
return self.response
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)
inital中的 self.check_throttles(request）会循环所有的限流类并执行限流类中的allow_request
def get_throttles(self):
#实例化自定义或全局的限流类并返回
return [throttle() for throttle in self.throttle_classes]
def check_throttles(self, request):
throttle_durations = []
for throttle in self.get_throttles():
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)
通过循环将我们的限流类全部实例化之后，会去执行限流类中的allow_request方法：
我们自己写的MyThrottle类继承SimpleRateThrottle
class SimpleRateThrottle(BaseThrottle):
...
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):
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 allow_request(self, request, view):
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()
在__init__ 方法中，通过self.rate=self.get_rate()给rate赋值，self.get_rate()的返回值会先从我们自己定义的 MyThrottle中寻找：从THROTTLE_RATES这个字典中获取scope这个键的值
scope = 'xxx'
THROTTLE_RATES = {'xxx':'5/m'}
如果我们有多个限流类，可以在限流类中定义scope然后在setting中设置scope对对应的键的值
REST_FRAMEWORK={
'DEFAULT_THROTTLE_RATES':{
'xxx':'5/m',
'x1':'10/m'
}
}
#self.rate获取到我们设置的速率后是一个字符串，会由self.parse_rate(self.rate)进行解析
class SimpleRateThrottle(BaseThrottle):
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 parse_rate(self, rate):
#按/进行分割，支持's','m','h','d',因为[period[0]]只读取/后的第一个字符，所以'5/min'或者‘5/hour'也是没问题的
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)
在循环实例每一个限流类时，self.num_requests, self.duration就可以获取到限制时间内的访问次数了，实例完后就会执行每一个限流类的allow_request（） （
#这是在上面的dispatch->initial->check_throttles
def check_throttles(self, request):
throttle_durations = []
for throttle in self.get_throttles():
if not throttle.allow_request(request, self):
#False就会将还需要等待的时间加入throttle_durations，将需要等待的时间加入throttle_durations
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
]
#因为可能有多个限流组件，所以有会取等待的最长时间
duration = max(durations, default=None)
#抛出异常
self.throttled(request, duration)
#####################超出限制速率，抛出异常#####################
def throttled(self, request, wait):
#超出限制速率，抛出异常
raise exceptions.Throttled(wait)
class Throttled(APIException):
status_code = status.HTTP_429_TOO_MANY_REQUESTS
default_detail = _('Request was throttled.')
extra_detail_singular = _('Expected available in {wait} second.')
extra_detail_plural = _('Expected available in {wait} seconds.')
default_code = 'throttled'
def __init__(self, wait=None, detail=None, code=None):
if detail is None:
detail = force_str(self.default_detail)
if wait is not None:
wait = math.ceil(wait)
detail = ' '.join((
detail,
force_str(ngettext(self.extra_detail_singular.format(wait=wait),
self.extra_detail_plural.format(wait=wait),
wait))))
self.wait = wait
super().__init__(detail, code)
##########################################################
def allow_request(self, request, view):
if self.rate is None:
return True
#获取用户的唯一标识
self.key = self.get_cache_key(request, view)
if self.key is None:
return True
#获取历史访问记录：[12:15,12:14,12:13，]
self.history = self.cache.get(self.key, [])
#获取当前时间戳
self.now = self.timer()
#pop掉当前时间减去设定的限流的时间间隔外的历史记录
while self.history and self.history[-1] <= self.now - self.duration:
self.history.pop()
#剩下的历史记录跟允许在限流的时间段内访问的次数比较
if len(self.history) >= self.num_requests:
#超过限制return False
return self.throttle_failure()
return self.throttle_success()
#成功将此条记录放在最前面，并缓存在redis
def throttle_success(self):
self.history.insert(0, self.now)
self.cache.set(self.key, self.history, self.duration)
return True
#如果allow_request返回了False,就会调用self.wait()
def wait(self):
if self.history:
#计算出还需等待多久
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)
