Django rest framework原始碼分析（3）----節流

目錄

新增節流

自定義節流的方法 

• 限制60s內只能訪問3次

（1）API資料夾下面新建throttle.py，程式碼如下：

# utils/throttle.py

from rest_framework.throttling import BaseThrottle
 
import time
VISIT_RECORD = {}   #儲存訪問記錄

class VisitThrottle(BaseThrottle):
    '''60s內只能訪問3次'''
    def __init__(self):
        self.history = None   #初始化訪問記錄

    def allow_request(self,request,view):
        #獲取使用者ip (get_ident)
        remote_addr = self.get_ident(request)
        ctime 
 
= time.time()
        #如果當前IP不在訪問記錄裡面，就新增到記錄
        if remote_addr not in VISIT_RECORD:
            VISIT_RECORD[remote_addr] = [ctime,]     #鍵值對的形式儲存
            return True    #True表示可以訪問
        #獲取當前ip的歷史訪問記錄
        history = VISIT_RECORD.get(remote_addr)
        #初始化訪問記錄
        self.history = history

        
 
#如果有歷史訪問記錄，並且最早一次的訪問記錄離當前時間超過60s，就刪除最早的那個訪問記錄，
        #只要為True，就一直迴圈刪除最早的一次訪問記錄
        while history and history[-1] < ctime - 60:
            history.pop()
        #如果訪問記錄不超過三次，就把當前的訪問記錄插到第一個位置（pop刪除最後一個）
        if len(history) < 3:
            history.insert(0,ctime)
            return True

    def wait(self):
        '''還需要等多久才能訪問'''
        ctime = time.time()
        return 60 - (ctime - self.history[-1])

（2）settings中全域性配置節流

#全域性
REST_FRAMEWORK = {
    #節流
    "DEFAULT_THROTTLE_CLASSES":['API.utils.throttle.VisitThrottle'],
}

（3）現在訪問auth看看結果：

• 60s內訪問次數超過三次，會限制訪問
• 提示剩餘多少時間可以訪問

接著訪問

節流原始碼分析

 （1）dispatch

 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
        #對原始request進行加工，豐富了一些功能
        #Request(
        #     request,
        #     parsers=self.get_parsers(),
        #     authenticators=self.get_authenticators(),
        #     negotiator=self.get_content_negotiator(),
        #     parser_context=parser_context
        # )
        #request(原始request,[BasicAuthentications物件，])
        #獲取原生request,request._request
        #獲取認證類的物件，request.authticators
        #1.封裝request
        request = self.initialize_request(request, *args, **kwargs)
        self.request = request
        self.headers = self.default_response_headers  # deprecate?

        try:
            #2.認證
            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

（2）initial

 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
        #4.實現認證
        self.perform_authentication(request)
        #5.許可權判斷
        self.check_permissions(request)
        #6.控制訪問頻率
        self.check_throttles(request)

（3）check_throttles

裡面有個allow_request

    def check_throttles(self, request):
        """
        Check if request should be throttled.
        Raises an appropriate exception if the request is throttled.
        """
        for throttle in self.get_throttles():
            if not throttle.allow_request(request, self):
                self.throttled(request, throttle.wait())

（4）get_throttles

    def get_throttles(self):
        """
        Instantiates and returns the list of throttles that this view uses.
        """
        return [throttle() for throttle in self.throttle_classes]

（5）thtottle_classes

 內建節流類

 上面是寫的自定義節流，drf內建了很多節流的類，用起來比較方便。

（1）BaseThrottle

• 自己要寫allow_request和wait方法
• get_ident就是獲取ip

class BaseThrottle(object):
    """
    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

（2）SimpleRateThrottle

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   #這個值自定義，寫什麼都可以
    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

        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()

    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)

我們可以通過繼承SimpleRateThrottle類，來實現節流，會更加的簡單，因為SimpleRateThrottle裡面都幫我們寫好了

（1）throttle.py

from rest_framework.throttling import SimpleRateThrottle

class VisitThrottle(SimpleRateThrottle):
    '''匿名使用者60s只能訪問三次（根據ip）'''
    scope = 'NBA'   #這裡面的值，自己隨便定義，settings裡面根據這個值配置Rate

    def get_cache_key(self, request, view):
        #通過ip限制節流
        return self.get_ident(request)

class UserThrottle(SimpleRateThrottle):
    '''登入使用者60s可以訪問10次'''
    scope = 'NBAUser'    #這裡面的值，自己隨便定義，settings裡面根據這個值配置Rate

    def get_cache_key(self, request, view):
        return request.user.username

（2）settings.py

#全域性
REST_FRAMEWORK = {
    #節流
    "DEFAULT_THROTTLE_CLASSES":['API.utils.throttle.UserThrottle'],   #全域性配置，登入使用者節流限制（10/m）
    "DEFAULT_THROTTLE_RATES":{
        'NBA':'3/m',         #沒登入使用者3/m，NBA就是scope定義的值
        'NBAUser':'10/m',    #登入使用者10/m，NBAUser就是scope定義的值
    }
}

（3）views.py

區域性配置方法

class AuthView(APIView):
    .
    .    
    .
    # 預設的節流是登入使用者（10/m）,AuthView不需要登入，這裡用匿名使用者的節流（3/m）
    throttle_classes = [VisitThrottle,]
　 　.
    .

from django.shortcuts import render,HttpResponse
from django.http import JsonResponse
from rest_framework.views import APIView
from API import models
from rest_framework.request import Request
from rest_framework import exceptions
from rest_framework.authentication import BaseAuthentication
from API.utils.permission import SVIPPremission,MyPremission
from API.utils.throttle import  VisitThrottle

ORDER_DICT = {
    1:{
        'name':'apple',
        'price':15
    },
    2:{
        'name':'dog',
        'price':100
    }
}

def md5(user):
    import hashlib
    import time
    #當前時間，相當於生成一個隨機的字串
    ctime = str(time.time())
    m = hashlib.md5(bytes(user,encoding='utf-8'))
    m.update(bytes(ctime,encoding='utf-8'))
    return m.hexdigest()


class AuthView(APIView):
    '''用於使用者登入驗證'''

    authentication_classes = []      #裡面為空，代表不需要認證
    permission_classes = []          #不裡面為空，代表不需要許可權
    # 預設的節流是登入使用者（10/m）,AuthView不需要登入，這裡用匿名使用者的節流（3/m）
    throttle_classes = [VisitThrottle,]

    def post(self,request,*args,**kwargs):
        ret = {'code':1000,'msg':None}
        try:
            user = request._request.POST.get('username')
            pwd = request._request.POST.get('password')
            obj = models.UserInfo.objects.filter(username=user,password=pwd).first()
            if not obj:
                ret['code'] = 1001
                ret['msg'] = '使用者名稱或密碼錯誤'
            #為使用者建立token
            token = md5(user)
            #存在就更新，不存在就建立
            models.UserToken.objects.update_or_create(user=obj,defaults={'token':token})
            ret['token'] = token
        except Exception as e:
            ret['code'] = 1002
            ret['msg'] = '請求異常'
        return JsonResponse(ret)


class OrderView(APIView):
    '''
    訂單相關業務(只有SVIP使用者才能看)
    '''

    def get(self,request,*args,**kwargs):
        self.dispatch
        #request.user
        #request.auth
        ret = {'code':1000,'msg':None,'data':None}
        try:
            ret['data'] = ORDER_DICT
        except Exception as e:
            pass
        return JsonResponse(ret)


class UserInfoView(APIView):
    '''
       訂單相關業務(普通使用者和VIP使用者可以看)
       '''
    permission_classes = [MyPremission,]    #不用全域性的許可權配置的話，這裡就要寫自己的區域性許可權
    def get(self,request,*args,**kwargs):

        print(request.user)
        return HttpResponse('使用者資訊')

views.py

說明：

• API.utils.throttle.UserThrottle   這個是全域性配置（根據ip限制，10/m）
• DEFAULT_THROTTLE_RATES      --->>>設定訪問頻率的
• throttle_classes = [VisitThrottle,]     --->>>區域性配置（不適用settings裡面預設的全域性配置）

 

總結

基本使用

• 建立類，繼承BaseThrottle, 實現：allow_request ，wait  
• 建立類，繼承SimpleRateThrottle,   實現：  get_cache_key， scope='NBA'      (配置檔案中的key)    

全域性

   #節流
    "DEFAULT_THROTTLE_CLASSES":['API.utils.throttle.UserThrottle'],   #全域性配置，登入使用者節流限制（10/m）
    "DEFAULT_THROTTLE_RATES":{
        'NBA':'3/m',         #沒登入使用者3/m，NBA就是scope定義的值
        'NBAUser':'10/m',    #登入使用者10/m，NBAUser就是scope定義的值
    }
}

區域性

throttle_classes = [VisitThrottle,]

所有程式碼

認證、許可權和節流

# MyProject/urls.py

from django.contrib import admin
from django.urls import path
from API.views import AuthView,OrderView,UserInfoView

urlpatterns = [
    path('admin/', admin.site.urls),
    path('api/v1/auth/',AuthView.as_view()),
    path('api/v1/order/',OrderView.as_view()),
    path('api/v1/info/',UserInfoView.as_view()),
]

MyProject/urls.py

#全域性
REST_FRAMEWORK = {
    #認證
    "DEFAULT_AUTHENTICATION_CLASSES":['API.utils.auth.Authentication',],
    #許可權
    "DEFAULT_PERMISSION_CLASSES":['API.utils.permission.SVIPPermission'],
    #節流
    "DEFAULT_THROTTLE_CLASSES":['API.utils.throttle.UserThrottle'],   #全域性配置，登入使用者節流限制（10/m）
    "DEFAULT_THROTTLE_RATES":{
        'NBA':'3/m',         #沒登入使用者3/m，NBA就是scope定義的值
        'NBAUser':'10/m',    #登入使用者10/m，NBAUser就是scope定義的值
    }
}

settings.py

# API/models.py


from django.db import models

class UserInfo(models.Model):
    USER_TYPE = (
        (1,'普通使用者'),
        (2,'VIP'),
        (3,'SVIP')
    )

    user_type = models.IntegerField(choices=USER_TYPE)
    username = models.CharField(max_length=32)
    password = models.CharField(max_length=64)

class UserToken(models.Model):
    user = models.OneToOneField(UserInfo,on_delete=models.CASCADE)
    token = models.CharField(max_length=64)

API/models.py

# API/views.py

from django.shortcuts import render,HttpResponse
from django.http import JsonResponse
from rest_framework.views import APIView
from API import models
from rest_framework.request import Request
from rest_framework import exceptions
from rest_framework.authentication import BaseAuthentication
from API.utils.permission import SVIPPermission,MyPermission
from API.utils.throttle import  VisitThrottle

ORDER_DICT = {
    1:{
        'name':'apple',
        'price':15
    },
    2:{
        'name':'dog',
        'price':100
    }
}

def md5(user):
    import hashlib
    import time
    #當前時間，相當於生成一個隨機的字串
    ctime = str(time.time())
    m = hashlib.md5(bytes(user,encoding='utf-8'))
    m.update(bytes(ctime,encoding='utf-8'))
    return m.hexdigest()


class AuthView(APIView):
    '''用於使用者登入驗證'''

    authentication_classes = []      #裡面為空，代表不需要認證
    permission_classes = []          #不裡面為空，代表不需要許可權
    # 預設的節流是登入使用者（10/m）,AuthView不需要登入，這裡用匿名使用者的節流（3/m）
    throttle_classes = [VisitThrottle,]

    def post(self,request,*args,**kwargs):
        ret = {'code':1000,'msg':None}
        try:
            user = request._request.POST.get('username')
            pwd = request._request.POST.get('password')
            obj = models.UserInfo.objects.filter(username=user,password=pwd).first()
            if not obj:
                ret['code'] = 1001
                ret['msg'] = '使用者名稱或密碼錯誤'
            #為使用者建立token
            token = md5(user)
            #存在就更新，不存在就建立
            models.UserToken.objects.update_or_create(user=obj,defaults={'token':token})
            ret['token'] = token
        except Exception as e:
            ret['code'] = 1002
            ret['msg'] = '請求異常'
        return JsonResponse(ret)


class OrderView(APIView):
    '''
    訂單相關業務(只有SVIP使用者才能看)
    '''

    def get(self,request,*args,**kwargs):
        self.dispatch
        #request.user
        #request.auth
        ret = {'code':1000,'msg':None,'data':None}
        try:
            ret['data'] = ORDER_DICT
        except Exception as e:
            pass
        return JsonResponse(ret)


class UserInfoView(APIView):
    '''
       訂單相關業務(普通使用者和VIP使用者可以看)
       '''
    permission_classes = [MyPermission,]    #不用全域性的許可權配置的話，這裡就要寫自己的區域性許可權
    def get(self,request,*args,**kwargs):

        print(request.user)
        return HttpResponse('使用者資訊')

API/views.py

# API/utils/auth/py

from rest_framework import exceptions
from API import models
from rest_framework.authentication import BaseAuthentication


class Authentication(BaseAuthentication):
    '''用於使用者登入驗證'''
    def authenticate(self,request):
        token = request._request.GET.get('token')
        token_obj = models.UserToken.objects.filter(token=token).first()
        if not token_obj:
            raise exceptions.AuthenticationFailed('使用者認證失敗')
        #在rest framework內部會將這兩個欄位賦值給request，以供後續操作使用
        return (token_obj.user,token_obj)

    def authenticate_header(self, request):
        pass

API/utils/auth/py

# utils/permission.py

from rest_framework.permissions import BasePermission

class SVIPPermission(BasePermission):
    message = "必須是SVIP才能訪問"
    def has_permission(self,request,view):
        if request.user.user_type != 3:
            return False
        return True


class MyPermission(BasePermission):
    def has_permission(self,request,view):
        if request.user.user_type == 3:
            return False
        return True

utils/permission.py

# utils/throttle.py
#
# from rest_framework.throttling import BaseThrottle
# import time
# VISIT_RECORD = {}   #儲存訪問記錄
#
# class VisitThrottle(BaseThrottle):
#     '''60s內只能訪問3次'''
#     def __init__(self):
#         self.history = None   #初始化訪問記錄
#
#     def allow_request(self,request,view):
#         #獲取使用者ip (get_ident)
#         remote_addr = self.get_ident(request)
#         ctime = time.time()
#         #如果當前IP不在訪問記錄裡面，就新增到記錄
#         if remote_addr not in VISIT_RECORD:
#             VISIT_RECORD[remote_addr] = [ctime,]     #鍵值對的形式儲存
#             return True    #True表示可以訪問
#         #獲取當前ip的歷史訪問記錄
#         history = VISIT_RECORD.get(remote_addr)
#         #初始化訪問記錄
#         self.history = history
#
#         #如果有歷史訪問記錄，並且最早一次的訪問記錄離當前時間超過60s，就刪除最早的那個訪問記錄，
#         #只要為True，就一直迴圈刪除最早的一次訪問記錄
#         while history and history[-1] < ctime - 60:
#             history.pop()
#         #如果訪問記錄不超過三次，就把當前的訪問記錄插到第一個位置（pop刪除最後一個）
#         if len(history) < 3:
#             history.insert(0,ctime)
#             return True
#
#     def wait(self):
#         '''還需要等多久才能訪問'''
#         ctime = time.time()
#         return 60 - (ctime - self.history[-1])

from rest_framework.throttling import SimpleRateThrottle

class VisitThrottle(SimpleRateThrottle):
    '''匿名使用者60s只能訪問三次（根據ip）'''
    scope = 'NBA'   #這裡面的值，自己隨便定義，settings裡面根據這個值配置Rate

    def get_cache_key(self, request, view):
        #通過ip限制節流
        return self.get_ident(request)

class UserThrottle(SimpleRateThrottle):
    '''登入使用者60s可以訪問10次'''
    scope = 'NBAUser'    #這裡面的值，自己隨便定義，settings裡面根據這個值配置Rate

    def get_cache_key(self, request, view):
        return request.user.username

utils/throttle.py

 end。。。

新增節流

節流原始碼分析

 內建節流類

（1）BaseThrottle

（2）SimpleRateThrottle

目錄

新增節流

自定義節流的方法 

• 限制60s內只能訪問3次

（1）API資料夾下面新建throttle.py，程式碼如下：

# utils/throttle.py

from rest_framework.throttling import BaseThrottle
import time
VISIT_RECORD = {}   #儲存訪問記錄

class VisitThrottle(BaseThrottle):
    '''60s內只能訪問3次'''
    def __init__(self):
        self.history = None   #初始化訪問記錄

    def allow_request(self,request,view):
        #獲取使用者ip (get_ident)
        remote_addr = self.get_ident(request)
        ctime = time.time()
        #如果當前IP不在訪問記錄裡面，就新增到記錄
        if remote_addr not in VISIT_RECORD:
            VISIT_RECORD[remote_addr] = [ctime,]     #鍵值對的形式儲存
            return True    #True表示可以訪問
        #獲取當前ip的歷史訪問記錄
        history = VISIT_RECORD.get(remote_addr)
        #初始化訪問記錄
        self.history = history

        #如果有歷史訪問記錄，並且最早一次的訪問記錄離當前時間超過60s，就刪除最早的那個訪問記錄，
        #只要為True，就一直迴圈刪除最早的一次訪問記錄
        while history and history[-1] < ctime - 60:
            history.pop()
        #如果訪問記錄不超過三次，就把當前的訪問記錄插到第一個位置（pop刪除最後一個）
        if len(history) < 3:
            history.insert(0,ctime)
            return True

    def wait(self):
        '''還需要等多久才能訪問'''
        ctime = time.time()
        return 60 - (ctime - self.history[-1])

（2）settings中全域性配置節流

#全域性
REST_FRAMEWORK = {
    #節流
    "DEFAULT_THROTTLE_CLASSES":['API.utils.throttle.VisitThrottle'],
}

（3）現在訪問auth看看結果：

• 60s內訪問次數超過三次，會限制訪問
• 提示剩餘多少時間可以訪問

接著訪問

節流原始碼分析

 （1）dispatch

 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
        #對原始request進行加工，豐富了一些功能
        #Request(
        #     request,
        #     parsers=self.get_parsers(),
        #     authenticators=self.get_authenticators(),
        #     negotiator=self.get_content_negotiator(),
        #     parser_context=parser_context
        # )
        #request(原始request,[BasicAuthentications物件，])
        #獲取原生request,request._request
        #獲取認證類的物件，request.authticators
        #1.封裝request
        request = self.initialize_request(request, *args, **kwargs)
        self.request = request
        self.headers = self.default_response_headers  # deprecate?

        try:
            #2.認證
            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

（2）initial

 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
        #4.實現認證
        self.perform_authentication(request)
        #5.許可權判斷
        self.check_permissions(request)
        #6.控制訪問頻率
        self.check_throttles(request)

（3）check_throttles

裡面有個allow_request

    def check_throttles(self, request):
        """
        Check if request should be throttled.
        Raises an appropriate exception if the request is throttled.
        """
        for throttle in self.get_throttles():
            if not throttle.allow_request(request, self):
                self.throttled(request, throttle.wait())

（4）get_throttles

    def get_throttles(self):
        """
        Instantiates and returns the list of throttles that this view uses.
        """
        return [throttle() for throttle in self.throttle_classes]

（5）thtottle_classes

 內建節流類

 上面是寫的自定義節流，drf內建了很多節流的類，用起來比較方便。

（1）BaseThrottle

• 自己要寫allow_request和wait方法
• get_ident就是獲取ip

class BaseThrottle(object):
    """
    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

（2）SimpleRateThrottle

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   #這個值自定義，寫什麼都可以
    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

        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()