基於 

當用發出請求時 首先執行dispatch函式，當執行當第二部時：

   #2.處理版本資訊 處理認證資訊 處理許可權資訊 對使用者的訪問頻率進行限制
            self.initial(request, *args, **kwargs)

進入到initial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.
 

        #2.1處理版本資訊
        version, scheme = self.determine_version(request, *args, **kwargs)
        request.version, request.versioning_scheme = version, scheme

        # Ensure that the incoming request is permitted
        #2.2處理認證資訊
        self.perform_authentication(request)
        
 
#2.3處理許可權資訊
        self.check_permissions(request)
        #2.4對使用者的訪問頻率進行限制
        self.check_throttles(request)

 #2.4對使用者的訪問頻率進行限制
        self.check_throttles(request)

限流的具體分析：

一、執行check_throttles方法

    def check_throttles(self, request):
        """
        Check if request should be throttled.
        Raises an appropriate exception if the request is throttled.
        """
        #遍歷throttle物件列表
        for throttle in self.get_throttles():
            #根據allow_request()的返回值進行下一步操作，返回True的話不執行下面程式碼，標識不限流，返回False的話執行下面程式碼，還可以丟擲異常
            if not throttle.allow_request(request, self):
                #返回False的話執行
                self.throttled(request, throttle.wait())

二、執行allow_request方法

首先找到BaseThrottle類，有好多類繼承了該類，並且都有allow_request方法，至於執行那個類中的allow_request方法，取決於我們自定義的Throttle這個類繼承誰

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')
    #獲取唯一標識,匿名使用者用ip地址，認證使用者用自己的user資訊
    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

三、具體分析以具有代表性的SimpleRateThrottle類分析

class SimpleRateThrottle(BaseThrottle):
    """
    A simple cache implementation, that only requires `.get_cache_key()`
    to be overridden.

    The rate (requests / seconds) is set by a `throttle` 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):
        #判斷是否有rate，實際上rate就是我們定義的scope的值
        if not getattr(self, 'rate', None):
            #沒有呼叫get_rate()獲取
            self.rate = self.get_rate()
        #num_requests代表具體的次數 duration代表具體的時間單位
        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.
        """
        #判斷當前類中我們定義的scope是否有值，沒有則丟擲異常，告訴我們必須設定scope
        if not getattr(self, 'scope', None):
            msg = ("You must set either `.scope` or `.rate` for '%s' throttle" %
                   self.__class__.__name__)
            raise ImproperlyConfigured(msg)

        try:
            #有的話直接返回scope對應的值
            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)
        #rate實際就是我們自定義的scope的值 如10/m(代表10次每分鐘)
        #按'/'切分num代表次數，period代表時間
        num, period = rate.split('/')
        #多少次
        num_requests = int(num)
        #獲取具體的時間單位
        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`.
        """
        #如果沒有rate也就是scope沒有值
        #如果沒有則表示不限流,
        if self.rate is None:
            return True

        #get_cache_key必須自己重寫,如果沒有則表示不限流
        #key一般是唯一標示如使用者名稱密碼 或者登陸者的ip地址
        self.key = self.get_cache_key(request, view)
        if self.key is None:
            return True
        #獲取當前key所對應的時間列表，也就是使用者每一次訪問的時間都放到該列表中
        self.history = self.cache.get(self.key, [])
        #當前時間
        self.now = self.timer()

        # Drop any requests from the history which have now passed the
        # throttle duration
        #當時間列表存在,並且當前時間已經超出了規定的時間
        while self.history and self.history[-1] <= self.now - self.duration:
            #把最開始加進去的時間刪除
            self.history.pop()
        #如果列表中的時間數大於規定執行的次數
        if len(self.history) >= self.num_requests:
            #則return False
            return self.throttle_failure()
        #return True
        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:
            #計算等待時間(也就是等待多久可以才可以訪問下一次)
            remaining_duration = self.duration - (self.now - self.history[-1])
        else:
            remaining_duration = self.duration

        #在規定的時間內還可以訪問多少次
        available_requests = self.num_requests - len(self.history) + 1
        if available_requests <= 0:
            return None

        return remaining_duration / float(available_requests)

四、回到第一步，執行allow_request方法

 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`.
        """
        #如果沒有rate也就是scope沒有值
        #如果沒有則表示不限流,
        if self.rate is None:
            return True

        #get_cache_key必須自己重寫,如果沒有則表示不限流
        #key一般是唯一標示如使用者名稱密碼 或者登陸者的ip地址
        self.key = self.get_cache_key(request, view)
        if self.key is None:
            return True
        #獲取當前key所對應的時間列表，也就是使用者每一次訪問的時間都放到該列表中
        self.history = self.cache.get(self.key, [])
        #當前時間
        self.now = self.timer()

        # Drop any requests from the history which have now passed the
        # throttle duration
        #當時間列表存在,並且當前時間已經超出了規定的時間
        while self.history and self.history[-1] <= self.now - self.duration:
            #把最開始加進去的時間刪除
            self.history.pop()
        #如果列表中的時間數大於規定執行的次數
        if len(self.history) >= self.num_requests:
            #則return False
            return self.throttle_failure()
        #return True
        return self.throttle_success()

五、根據allow_request方法的返回值確定具體執行，返回False的話執行

#根據allow_request()的返回值進行下一步操作，返回True的話不執行下面程式碼，標識不限流，返回False的話執行下面程式碼，還可以丟擲異常
            if not throttle.allow_request(request, self):
                #返回False的話執行
                self.throttled(request, throttle.wait())

 def throttled(self, request, wait):
        """
        If request is throttled, determine what kind of exception to raise.
        """
        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_text(self.default_detail)
        if wait is not None:
            wait = math.ceil(wait)
            detail = ' '.join((
                detail,
                force_text(ungettext(self.extra_detail_singular.format(wait=wait),
                                     self.extra_detail_plural.format(wait=wait),
                                     wait))))
        self.wait = wait
        super(Throttled, self).__init__(detail, code)

 

例子：繼承BaseThrottle

  url(r'^limit/', app03_views.Limitview.as_view()),

import time

from django.shortcuts import render
from rest_framework.views import APIView
from rest_framework.response import Response
from rest_framework.throttling import BaseThrottle
from rest_framework import exceptions
# Create your views here.


AllOW={}

class MyThrottle(BaseThrottle):
    '''
    要求每分鐘只能訪問十次
    '''
    ip = '1.1.1.1'
    def allow_request(self, request, view):

        ctime=time.time()
        ip=self.ip
        if ip not in AllOW:
            AllOW[ip]=[ctime,]
        else:
            time_list=AllOW[ip]
            while True:
                if ctime-60>time_list[-1]:
                    time_list.pop()
                else :
                    break
            if len(AllOW[ip])>10:
                return False
            AllOW[ip].insert(0,ctime)
        return True

    def wait(self):
        ip=self.ip
        ctime=time.time()
        first_in_time=AllOW[ip][-1]
        wt=60-(ctime-first_in_time)
        return wt





class Limitview(APIView):
    throttle_classes=[MyThrottle,]
    def get(self,reques):
        self.dispatch()
        return Response('歡迎訪問')

    def throttled(self,request,wait):
        class InnerThrottled(exceptions.Throttled):
            default_detail = '請求被限制.'
            extra_detail_singular = 'Expected available in {wait} second.'
            extra_detail_plural = '還需要再等待{wait}秒'

        raise InnerThrottled(wait)

Views

REST_FRAMEWORK = {
    'UNAUTHENTICATED_USER': None,
    'UNAUTHENTICATED_TOKEN': None,
    "DEFAULT_AUTHENTICATION_CLASSES": [
      # "app01.utils.MyAuthentication",
        "app02.utils.MyAuthentication",
    ],
    "DEFAULT_PERMISSION_CLASSES":[
       "app02.utils.MyPermission",
       "app02.utils.AdminPermission",
    ],
}

settings

seetings中沒有配置跟Throttle有的的資訊

繼承SimpleRateThrottle

  url(r'^limit/', app03_views.Limitview.as_view()),

urls

import time

from django.shortcuts import render
from rest_framework.views import APIView
from rest_framework.response import Response
from rest_framework.throttling import BaseThrottle
from rest_framework.throttling import SimpleRateThrottle
from rest_framework import exceptions
# Create your views here.


AllOW={}

class MyThrottle(BaseThrottle):
    '''
    要求每分鐘只能訪問十次
    '''
    ip = '1.1.1.1'
    def allow_request(self, request, view):

        ctime=time.time()
        ip=self.ip
        if ip not in AllOW:
            AllOW[ip]=[ctime,]
        else:
            time_list=AllOW[ip]
            while True:
                if ctime-60>time_list[-1]:
                    time_list.pop()
                else :
                    break
            if len(AllOW[ip])>10:
                return False
            AllOW[ip].insert(0,ctime)
        return True

    def wait(self):
        ip=self.ip
        ctime=time.time()
        first_in_time=AllOW[ip][-1]
        wt=60-(ctime-first_in_time)
        return wt


class MySimpleRateThrottle(SimpleRateThrottle):
    #必須要寫因為SimpleRateThrottle中要求了必須寫
    '''
     def get_rate(self):
        """
        Determine the string representation of the allowed request rate.
        """
        #判斷當前類中我們定義的scope是否有值，沒有則丟擲異常，告訴我們必須設定scope
        if not getattr(self, 'scope', None):
            msg = ("You must set either `.scope` or `.rate` for '%s' throttle" %
                   self.__class__.__name__)
            raise ImproperlyConfigured(msg)
    '''
    scope = 'tiga'

    #也必須必須要寫
    '''
        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_cache_key(self, request, view):
        return self.get_ident(request)



class Limitview(APIView):
    throttle_classes=[MySimpleRateThrottle,]
    def get(self,reques):
        return Response('歡迎訪問')

    def throttled(self,request,wait):
        class InnerThrottled(exceptions.Throttled):
            default_detail = '請求被限制.'
            extra_detail_singular = 'Expected available in {wait} second.'
            extra_detail_plural = '還需要再等待{wait}秒'

        raise InnerThrottled(wait)

Views

from django.db import models

# Create your models here.
class Userinfo(models.Model):
    name=models.CharField(max_length=32,verbose_name='使用者名稱')
    pwd=models.CharField(max_length=32,verbose_name='密碼')
    token=models.CharField(max_length=64,null=True)

    def __str__(self):
        return self.name

View Code

REST_FRAMEWORK = {
    'UNAUTHENTICATED_USER': None,
    'UNAUTHENTICATED_TOKEN': None,
    "DEFAULT_AUTHENTICATION_CLASSES": [
      # "app01.utils.MyAuthentication",
        "app02.utils.MyAuthentication",
    ],
    "DEFAULT_PERMISSION_CLASSES":[
       "app02.utils.MyPermission",
       "app02.utils.AdminPermission",
    ],
    "DEFAULT_THROTTLE_RATES":{
       'tiga':'10/m',
    }
}

settings

認證，許可權，限流綜合聯絡

    url(r'^index/', app04_views.IndexView.as_view()),
    url(r'^user/', app04_views.UserView.as_view()),
    url(r'^manage/', app04_views.ManageView.as_view()),

urls

from django.shortcuts import render
from rest_framework.views import APIView
from rest_framework.response import Response
from rest_framework.authentication import BaseAuthentication
from rest_framework.permissions import BasePermission
from rest_framework.throttling import SimpleRateThrottle
from rest_framework import exceptions

from app01 import models

# Create your views here.
class MyAuthentication(BaseAuthentication):
    def authenticate(self, request):
        token=request.query_params.get('token')
        user=models.Userinfo.objects.filter(token=token).first()
        if user:
            return (user.name,user)
        return None

class UserPermission(BasePermission):
    message='登入使用者才可以訪問'
    def has_permission(self, request, view):
        if request.user:
            return True
        return False
class AdminPermission(BasePermission):
    message='管理員才能訪問'
    def has_permission(self, request, view):
        if request.user =='ctz':
            return True
        return False


class AnnoThrottle(SimpleRateThrottle):
    scope = 'anno'
    def get_cache_key(self, request, view):
        #如果是匿名使用者則執行
        if not request.user:
            return self.get_ident(request)
        #如果不是匿名使用者則讓他執行
        return None

class UserThrottle(SimpleRateThrottle):
    scope = 'user'

    def get_cache_key(self, request, view):
        #當前使用者登陸了,並且當前使用者不是管理員
        if request.user and request.user!='ctz':
            return self.get_ident(request)
        #如果是匿名使用者和管理員 則讓他繼續執行
        return None

class AdminThrottle(SimpleRateThrottle):
    scope = 'admin'

    def get_cache_key(self, request, view):
        #如果是管理員
        if request.user=='ctz':
            return self.get_ident(request)
        #不是管理員
        return  None

class IndexView(APIView):
    '''
    要求,所有使用者都能訪問，匿名使用者5/m,普通使用者10/m,管理員不限
    '''
    authentication_classes = [MyAuthentication,]
    permission_classes = []
    throttle_classes = [AnnoThrottle,UserThrottle,AdminThrottle]
    def get(self,request):
        return Response('首頁')

    def throttled(self, request, wait):
        class UserInnerThrottled(exceptions.Throttled):
            default_detail = '請求被限制.'
            extra_detail_singular = 'Expected available in {wait} second.'
            extra_detail_plural = '還需要再等待{wait}秒'
        raise UserInnerThrottled(wait)



class UserView(APIView):
    '''
    要求:登入使用者能訪問,普通使用者10/m,管理員20/m
    '''
    authentication_classes = [MyAuthentication,]
    permission_classes = [UserPermission,]
    throttle_classes = [UserThrottle,AdminThrottle]
    def get(self,request):
        return Response('使用者介面')

    def permission_denied(self, request, message=None):
        """
        If request is not permitted, determine what kind of exception to raise.
        """

        if request.authenticators and not request.successful_authenticator:
            raise exceptions.NotAuthenticated('無權訪問')
        raise exceptions.PermissionDenied(detail=message)


    def throttled(self, request, wait):
        class UserInnerThrottled(exceptions.Throttled):
            default_detail = '請求被限制.'
            extra_detail_singular = 'Expected available in {wait} second.'
            extra_detail_plural = '還需要再等待{wait}秒'
        raise UserInnerThrottled(wait)

class ManageView(APIView):
    '''
    要求:只有管理園能訪問,5/m
    '''
    authentication_classes = [MyAuthentication,]
    permission_classes = [AdminPermission,]
    throttle_classes = [AdminThrottle]
    def get(self,request):
        return Response('管理員介面')

    def permission_denied(self, request, message=None):
        """
        If request is not permitted, determine what kind of exception to raise.
        """

        if request.authenticators and not request.successful_authenticator:
            raise exceptions.NotAuthenticated('無權訪問')
        raise exceptions.PermissionDenied(detail=message)

    def throttled(self, request, wait):
        class UserInnerThrottled(exceptions.Throttled):
            default_detail = '請求被限制.'
            extra_detail_singular = 'Expected available in {wait} second.'
            extra_detail_plural = '還需要再等待{wait}秒'
        raise UserInnerThrottled(wait)

Views

from django.db import models

# Create your models here.
class Userinfo(models.Model):
    name=models.CharField(max_length=32,verbose_name='使用者名稱')
    pwd=models.CharField(max_length=32,verbose_name='密碼')
    token=models.CharField(max_length=64,null=True)

    def __str__(self):
        return self.name

models

REST_FRAMEWORK = {
    'UNAUTHENTICATED_USER': None,
    'UNAUTHENTICATED_TOKEN': None,
    "DEFAULT_AUTHENTICATION_CLASSES": [
      # "app01.utils.MyAuthentication",
        "app02.utils.MyAuthentication",
    ],
    "DEFAULT_PERMISSION_CLASSES":[
       "app02.utils.MyPermission",
       "app02.utils.AdminPermission",
    ],
    "DEFAULT_THROTTLE_RATES":{
       'tiga':'10/m',
       'anno':'5/m',
       'user':'10/m',
       'admin':'20/m',
    }
}

settings

 

 

基於 

當用發出請求時 首先執行dispatch函式，當執行當第二部時：

   #2.處理版本資訊 處理認證資訊 處理許可權資訊 對使用者的訪問頻率進行限制
            self.initial(request, *args, **kwargs)

進入到initial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.
        #2.1處理版本資訊
        version, scheme = self.determine_version(request, *args, **kwargs)
        request.version, request.versioning_scheme = version, scheme

        # Ensure that the incoming request is permitted
        #2.2處理認證資訊
        self.perform_authentication(request)
        #2.3處理許可權資訊
        self.check_permissions(request)
        #2.4對使用者的訪問頻率進行限制
        self.check_throttles(request)

 #2.4對使用者的訪問頻率進行限制
        self.check_throttles(request)

限流的具體分析：

一、執行check_throttles方法

    def check_throttles(self, request):
        """
        Check if request should be throttled.
        Raises an appropriate exception if the request is throttled.
        """
        #遍歷throttle物件列表
        for throttle in self.get_throttles():
            #根據allow_request()的返回值進行下一步操作，返回True的話不執行下面程式碼，標識不限流，返回False的話執行下面程式碼，還可以丟擲異常
            if not throttle.allow_request(request, self):
                #返回False的話執行
                self.throttled(request, throttle.wait())

二、執行allow_request方法

首先找到BaseThrottle類，有好多類繼承了該類，並且都有allow_request方法，至於執行那個類中的allow_request方法，取決於我們自定義的Throttle這個類繼承誰

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')
    #獲取唯一標識,匿名使用者用ip地址，認證使用者用自己的user資訊
    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

三、具體分析以具有代表性的SimpleRateThrottle類分析

class SimpleRateThrottle(BaseThrottle):
    """
    A simple cache implementation, that only requires `.get_cache_key()`
    to be overridden.

    The rate (requests / seconds) is set by a `throttle` 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):
        #判斷是否有rate，實際上rate就是我們定義的scope的值
        if not getattr(self, 'rate', None):
            #沒有呼叫get_rate()獲取
            self.rate = self.get_rate()
        #num_requests代表具體的次數 duration代表具體的時間單位
        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.
        """
        #判斷當前類中我們定義的scope是否有值，沒有則丟擲異常，告訴我們必須設定scope
        if not getattr(self, 'scope', None):
            msg = ("You must set either `.scope` or `.rate` for '%s' throttle" %
                   self.__class__.__name__)
            raise ImproperlyConfigured(msg)

        try:
            #有的話直接返回scope對應的值
            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)
        #rate實際就是我們自定義的scope的值 如10/m(代表10次每分鐘)
        #按'/'切分num代表次數，period代表時間
        num, period = rate.split('/')
        #多少次
        num_requests = int(num)
        #獲取具體的時間單位
        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`.
        """
        #如果沒有rate也就是scope沒有值
        #如果沒有則表示不限流,
        if self.rate is None:
            return True

        #get_cache_key必須自己重寫,如果沒有則表示不限流
        #key一般是唯一標示如使用者名稱密碼 或者登陸者的ip地址
        self.key = self.get_cache_key(request, view)
        if self.key is None:
            return True
        #獲取當前key所對應的時間列表，也就是使用者每一次訪問的時間都放到該列表中
        self.history = self.cache.get(self.key, [])
        #當前時間
        self.now = self.timer()

        # Drop any requests from the history which have now passed the
        # throttle duration
        #當時間列表存在,並且當前時間已經超出了規定的時間
        while self.history and self.history[-1] <= self.now - self.duration:
            #把最開始加進去的時間刪除
            self.history.pop()
        #如果列表中的時間數大於規定執行的次數
        if len(self.history) >= self.num_requests:
            #則return False
            return self.throttle_failure()
        #return True
        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:
            #計算等待時間(也就是等待多久可以才可以訪問下一次)
            remaining_duration = self.duration - (self.now - self.history[-1])
        else:
            remaining_duration = self.duration

        #在規定的時間內還可以訪問多少次
        available_requests = self.num_requests - len(self.history) + 1
        if available_requests <= 0:
            return None