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作者:百年不渡  分类:未来幻想  点击:688240次  下载:5次  大小:70M  日期:2019-06-26

斐济_Django Rest Framework源码剖析(三)-----频率控制

标签:家学渊源 金门县

一、简介

承接上篇文章Django Rest Framework源码剖析(二)-----权限,当服务的接口被频繁调用,导致资源紧张怎么办呢?当然或许有很多解决办法,比如:负载均衡、提高服务器配置、通过代理限制访问频率等,但是django rest framework自身就提供了访问频率的控制,可以从代码本身做控制。

二、频率控制内部原理概述

django rest framework 中频率控制基本原理基于访问次数和时间,通过计算实现,当然我们也可以自己定义频率控制方法。基本原理如下:

启用频率,DRF内部会有一个字典记录来访者的IP,以及访问时间最近几(通过配置)次的访问时间,这样确保每次列表中最后一个元素都是该用户请求的最早时间,形式如下:

{
IP1:[第三次请求时间,第二次请求时间,第一次请求时间,],
IP2:[第二次请求时间,第一次请求时间,],
.....
}

举例说明,比如我现在配置了5秒内只能访问2次,每次请求到达频率控制时候先判断请求者IP是否已经在这个请求字典中,若存在,在判断用户请求5秒内的请求次数,若次数小于等于2,则允许请求,若大于2,则超过频率,不允许请求。

关于请求频率的的算法(以5秒内最多访问两次为例):

1.首先删除掉列表里5秒之前的请求,循环判断当前请求时间和最早请求时间之差记作t1,若t1大于5则代表列表中最早的请求已经在5秒外了,删除掉,继续判断倒数第二个请求,直到t1小于5.

2.当确保请求列表中只有5秒内请求时候,接着判断其请求次数(列表长度),若长度大于2,则证明超过5秒内访问超过2次了,则不允许,否则,通过并将此次访问时间插入到列表最前面,作为最新访问时间。

三、基本使用

同样,先来了解下频率控制的使用方法,后面在分析源码

1.在utils目录下新建立文件,throttle.py,添加频率控制为每分钟只能访问5次

#!/usr/bin/env python3
#_*_ coding:utf-8 _*_
#Author:wd
from rest_framework.throttling import SimpleRateThrottle

class VisitThrottle(SimpleRateThrottle):
    """5秒内最多访问三次"""
    scope = "WD"  #settings配置文件中的key,用于获取配置的频率

    def get_cache_key(self, request, view):
        return self.get_ident(request)

2.settings.py中配置全局频率控英雄_2018年最新新闻网

REST_FRAMEWORK = {
    #频率控制配置
    "DEFAULT_THROTTLE_CLASSES":["utils.throttle.VisitThrottle"],   #全局配置,
    "DEFAULT_THROTTLE_RATES":{
        "WD":"5/m",         #速率配置每分钟不能超过5次访问,WD是scope定义的值,

    }
}

urls.py

from django.conf.urls import url
from django.contrib import admin
from app01 import views

urlpatterns = [

    url(r"^api/v1/auth", views.AuthView.as_view()),
    url(r"^api/v1/order", views.OrderView.as_view()),
]

models.py

from django.db import models

class UserInfo(models.Model):
    user_type_choice = (
        (1,"普通用户"),
        (2,"会员"),
    )
    user_type = models.IntegerField(choices=user_type_choice)
    username = models.Ch风车_2018年最新新闻网arField(max_length=32,unique=True)
    password = models.CharField(max_length=64)


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

订单视图

class OrderView(APIView):
    """查看订单"""
    from utils.permissions import MyPremission
    authentication_classes = [Authentication,]    #添加认证
    permission_classes = [MyPremission,]           #添加权限控制
    def get(self,request,*args,**kwargs):
        #request.user
        #request.auth
        ret = {"code":1000,"msg":"你的订单已经完成","data":"买了一个mac"}
        return JsonResponse(ret,safe=True)

使用postman验证如下图,可以看到频率限制已经起作用了。

四、频率控制源码剖析

在前面几篇文章中已经分析了DRF的认证、权限源码,频率控制也一样也从APIView的dispatch方法说起,参考注解:

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
        #对原始request进行加工,丰富了一些功能
        #Request(
        #     request,
        #     parsers=self.get_parsers(),
        #     authenticators=self.get_authenticators(),
        #     negotiator=self.get_content_negotiator(),
        #     parser_context=parser_context
        # )
        #request(原始request,[BasicAuthentications对象,])
        #获取原生request,request._request
        #获取认证类的对象,request.authticators
        #1.封装request
        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

2.执行inital方法,initial方法中执行check_throttles则开始频率控制

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
        #2.实现认证
        self.perform_authentication(request)
        #3.权限判断
        self.check_permissions(request)
        #4.频率限制
        self.check_throttles(request)    

3.下面是check_throttles源码,与认证、权限一样采用列表对象方式,通过判断allow_request方法返回值判断频率是否通过

  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(): #循环频率控制类结果
            if not throttle.allow_request(request, self): #判断其中的allow_re终极一家_2018年最新新闻网questf返回结果,true则频率通过,否则返回等待多少秒可以访问
                self.throttled(request, throttle.wait())

4.get_throttles方法,采用列表生成式生成频率控制对象,与认证、权限一直

    def get_throttles(self):
        """
        Instantiates and returns the list of throttles that this view uses.
        """
        return [throttle() for throttle in self.throttle_classes] #列表生成式生成控制频率对象列表

5.self.throttle_classes属性获取

class APIView(View):

    # The following policies may be set at either globally, or per-view.
    renderer_classes = api_settings.DEFAULT_RENDERER_CLASSES
    parser_classes = api_settings.DEFAULT_PARSER_CLASSES
    authentication_classes = api_settings.DEFAULT_AUTHENTICATION_CLASSES
    throttle_classes = api_settings.DEFAULT_THROTTLE_CLASSES     #频率控制全局配置
    permission_classes = api_settings.DEFAULT_PERMISSION_CLASSES
    content_negotiation_class = api_settings.DEFAULT_CONTENT_NEGOTIATION_CLASS
    metadata_class = api_settings.DEFAULT_METADATA_CLASS
    versioning_class = api_settings.DEFAULT_VERSIONING_CLASS

6.通过以上分析,知道了频率控制是通过判断每个类中的allow_request放法的返回值来判断频率是否通过,下面我们来看看我们所使用的SimpleRateThrottle怎么实现的,分析部分请看注解:

SimpleRateThrottle类源码:

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  # 存放请求时间,类似与示例中的大字典,这里使用的是django的缓存
    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):
# 获取请求的key标识,必须要有否则会报错,这里可以重写,使用用户的用户名、或其他作为key,在示例中使用的get_ident方法用户获取用户IP作为key
""" 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): # 获取配置文件的配置速率 """ Determine the string representation of the allowed request rate. """ if not getattr(self, "scope", None): # 通过获取共有属性scope来获取配置的速率 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): # 格式化速率 """ 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("/") # 分离字符串 num_requests = int(num) duration = {"s": 1, "m": 60, "h": 3600, "d": 86400}[period[0]] # 转换时间为数字,示例配置的5/m,m转为60秒 return (num_requests, duration) def allow_request(self, request, view): # 判断请求的速率是否通过 """ 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爱情魔发师_2018年最新新闻网 while self.history and self.history[-1] <= self.now - self.duration: # 频率判断实现原理,已经举例进行了说明 self.history.pop() if len(self.history) >= self.num_requests: return self.throttle_failure() return self.throttle_success() def throttle_success(self): # 频率通过返回true """ 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): # 不通过返回false """ Called when a request to the API has failed due to throttling. """ return False def wait(self): # 返回等待时间 """ 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)

get_ident方法源码,该方法用于获取请求的IP:

    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 =等着我_2018年最新新闻网 request.META.get("REMOTE_ADDR")
        #这里request是封装以后的requst,django原生的是request._request.META 这样也可以获取
        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
五、内置频率控制类

DRF内置了多种频率控制类提供我们使用,其核心原理都是通过判断request_allow方法返回值来判断频率是否通过,通过wait方法返回等待时间。

1.BaseThrottle:最基本的频率控制需要重写allow_request方法和wait方法

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
class BaseThrottle(object)

2.SimpleRateThrottle:示例中已经使用,并对源码和原理进行了分析。

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

    The rate (requests / seconds) is set by a `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, ra妈妈咪呀_2018年最新新闻网te):
        """
        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)
View Code

3.AnonRateThrottle:匿名用户频率控制

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)
        }
AnonRateThrottle

4.UserRateThrottle:基于SimpleRateThrottle,对用户的频率控制

class UserRateThrottle(SimpleRateThrottle):
    """
    Limits the rate of API calls that may be made by a given user.

    The user id will be used as a unique cache key if the user is
    authenticated.  For anonymous requests, the IP address of the request will
    be used.
    """
    scope = "user"

    def get_cache_key(self, request, view):
        if request.user.is_authenticated:
            ident = request.user.pk
        else:
            ident = self.get_ident(request)

        return self.cache_format % {
            "scope": self.scope,
            "ident": ident
        }
UserRateThrottle
六、自定义频率控制

自定义频率控制无非实现request_allow方法和wait方法,你可以根据实际需求来定制你的频率控制,下面是示例:

from rest_framework.throttling import BaseThrottle
import time

REQUEST_RECORD = {}  # 访问记录,可使用nosql数据库


class VisitThrottle(BaseThrottle):
    """60s内最多能访问5次"""

    def __init__(self):
        self.history = None

    def allow_request(self, request, view):
        # 获取用户ip (get_ident)
        remote_addr = self.get_ident(request)
        ctime = time.time()

        if remote_addr not in REQUEST_RECORD:
            REQUEST_RECORD[remote_addr] = [ctime, ]  # 保持请求的时间,形式{ip:[时间,]}
            return True  # True表示可以访问
        # 获取当前ip的历史访问记录
        history = REQUEST_RECORD.get(remote_addr)
       
        self.history = history

       
        while history and history[-1] < ctime - 60:
            # while循环确保每列表中是最新的60秒内的请求
            
            history.pop()
        # 访问记录小于5次,将本次请求插入到最前面,作为最新的请求
        if len(history) < 5:
            history.insert(0, ctime)
            return True

    def wait(self):
        """返回等待时间"""
        ctime = time.time()
        return 60 - (ctime - self.history[-1])
七、总结

1.使用方法:

  • 继承BaseThrottle类
  • 重写request_allow方法和wait方法,request_allow方法返回true代表通过,否则拒绝,wait返回等待的时间

2.配置

###全局使用

REST_FRAMEWORK = {
    #频率控制配置
    "DEFAULT_THROTTLE_CLASSES":["utils.throttle.VisitThrottle"],   #全局配置,
    "DEFAULT_THROTTLE_RATES":{
        "WD":"5/m",         #速率配置每分钟不能超过5次访问,WD是scope定义的值

    }
}

##单一视图使用
throttle_classes = [VisitThrottle,]

##优先级
单一视图>全局

当前文章:http://hbacy-jieguowen-com.tongdating.cn/p31/ec0a9_158660.html

发布时间:2019-06-26 20:17:30

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