如果客户端很频繁的请求服务器，会给给服务器造成很大的压力，需要对客户端对API的请求，做一些限制，如Python 爬虫对服务器API的请求，对API的请求限制也是反爬虫的一个手段之一，那如何实现对API的访问的限制呢？
image
实现API接口
一个基本的API接口实现，没有任何的限制，客户端可以随意访问，也没有访问限制
[HttpGet]
[Route("~/api/helloworld")]public HttpResponseMessage HelloWorld(){ return Request.CreateResponse(HttpStatusCode.OK, "Hello World");
}添加基本的限制
如果要做限制，首先想到的是在访问这个接口时，做一个计数器，记录访问的数量，达到一定的数量之后就不能访问，使用cache来实现计数
[HttpGet]
[Route("~/api/helloworld")]public HttpResponseMessage HelloWorld(){ int? requestCount = (int?)System.Web.HttpRuntime.Cache["throttle"]; if (!requestCount.HasValue) requestCount = 0;
requestCount++;
HttpRuntime.Cache["throttle"] = requestCount; if (requestCount > 10) return Request.CreateResponse((HttpStatusCode)429, "Too many requests"); return Request.CreateResponse(HttpStatusCode.OK, "Hello World");
}这样如果访问 /api/helloworld 这个接口超过10次，就返回 429错误，但是这个实现是不能用于生产环境的，只能演示使用，虽然实现了访问限制，但是超过了次数之后，就无法访问这个接口了，这不是我们想要的，期望的是限制一段时间之后，用户可以重新访问这个API
添加过期时间
改造一下上面的代码，对访问的限制添加一个过期时间，如果超过了限制了，会在一段时间之后，就可以继续访问了
[HttpGet]
[Route("~/api/helloworld")]public HttpResponseMessage HelloWorld(){
ThrottleInfo throttleInfo = (ThrottleInfo)HttpRuntime.Cache["throttle"]; if (throttleInfo == null)
throttleInfo = new ThrottleInfo {
ExpiresAt = DateTime.Now.AddSeconds(10), RequestCount = 0 };
throttleInfo.RequestCount++;
HttpRuntime.Cache.Add("throttle", throttleInfo, null,
throttleInfo.ExpiresAt, Cache.NoSlidingExpiration,
CacheItemPriority.Normal, null); if (throttleInfo.RequestCount > 10) return Request.CreateResponse((HttpStatusCode)429, "Too many requests"); return Request.CreateResponse(HttpStatusCode.OK, "Hello World");
}private class ThrottleInfo{ public DateTime ExpiresAt { get; set; } public int RequestCount { get; set; }
}这样访问超过了限制，等一段时间，就可以继续访问了
封装一下代码,将访问限制的代码提取出来
public HttpResponseMessage HelloWorld(){
var throttler = new Throttler("helloworld"); if (throttler.RequestShouldBeThrottled()) return Request.CreateResponse(
(HttpStatusCode)429, "Too many requests"); return Request.CreateResponse(HttpStatusCode.OK, "Hello World");
}public class Throttler{
private int _requestLimit; private int _timeoutInSeconds; private string _key; public Throttler(string key, int requestLimit = 5, int timeoutInSeconds = 10)
{
_requestLimit = requestLimit;
_timeoutInSeconds = timeoutInSeconds;
_key = key;
} public bool RequestShouldBeThrottled()
{
ThrottleInfo throttleInfo = (ThrottleInfo)HttpRuntime.Cache[_key]; if (throttleInfo == null) throttleInfo = new ThrottleInfo {
ExpiresAt = DateTime.Now.AddSeconds(_timeoutInSeconds),
RequestCount = 0
};
throttleInfo.RequestCount++;
HttpRuntime.Cache.Add(_key,
throttleInfo,
null,
throttleInfo.ExpiresAt,
Cache.NoSlidingExpiration,
CacheItemPriority.Normal,
null); return (throttleInfo.RequestCount > _requestLimit);
} private class ThrottleInfo
{
public DateTime ExpiresAt { get; set; } public int RequestCount { get; set; }
}
}不一定需要依赖 HttpRuntime.Cache,使用 ConcurrentDictionary 实现cache
public class Throttler{
private int _requestLimit; private int _timeoutInSeconds; private string _key; private static ConcurrentDictionary<string, ThrottleInfo> _cache = new ConcurrentDictionary<string, ThrottleInfo>(); public Throttler(string key, int requestLimit = 5, int timeoutInSeconds = 10)
{
_requestLimit = requestLimit;
_timeoutInSeconds = timeoutInSeconds;
_key = key;
} public bool RequestShouldBeThrottled()
{
ThrottleInfo throttleInfo = _cache.ContainsKey(_key) ? _cache[_key] : null; if (throttleInfo == null || throttleInfo.ExpiresAt <= DateTime.Now)
{
throttleInfo = new ThrottleInfo {
ExpiresAt = DateTime.Now.AddSeconds(_timeoutInSeconds),
RequestCount = 0};
};
throttleInfo.RequestCount++;
_cache[_key] = throttleInfo; return (throttleInfo.RequestCount > _requestLimit);
} private class ThrottleInfo
{
public DateTime ExpiresAt { get; set; } public int RequestCount { get; set; }
}
}使用user id作为key，也可以使用IP地址作为key
UserName作为key
[HttpGet]
[Route("~/api/helloworld")]public HttpResponseMessage HelloWorld(){
var throttler = new Throttler(User.Identity.Name);
}使用IP地址作为key
[HttpGet]
[Route("~/api/helloworld")]public HttpResponseMessage HelloWorld()
{ var ipAddress = System.Web.HttpContext.Current.Request.ServerVariables["REMOTE_ADDR"]; var throttler = new Throttler(ipAddress);
}让客户端知道访问限制，已经过期时间等
封装一下返回结果
public HttpResponseMessage HelloWorld(){
var throttler = new Throttler(User.Identity.Name);
HttpResponseMessage response = createResponse("Hello World", throttler); return response;
}private HttpResponseMessage createResponse(object content, Throttler throttler){
HttpResponseMessage response; if (throttler.RequestShouldBeThrottled())
response = Request.CreateResponse((HttpStatusCode)429, "Too many requests"); else
response = Request.CreateResponse(HttpStatusCode.OK, content);
response.Headers.Add("X-RateLimit-Limit", throttler.RequestLimit.ToString());
response.Headers.Add("X-RateLimit-Remaining", throttler.RequestsRemaining.ToString());
response.Headers.Add("X-RateLimit-Reset", toUnixTime(throttler.WindowResetDate).ToString()); return response;
}private long toUnixTime(DateTime date){
var epoch = new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc); return Convert.ToInt64((date.ToUniversalTime() - epoch).TotalSeconds);
}在返回的结果中添加了三个 header ，重构一下 Throttler来支持这个三个属性
public class Throttler{
public int RequestLimit { get; private set; } public int RequestsRemaining { get; private set; } public DateTime WindowResetDate { get; private set; } private static ConcurrentDictionary<string, ThrottleInfo> _cache = new ConcurrentDictionary<string, ThrottleInfo>(); private string _key; private int _timeoutInSeconds; public Throttler(string key, int requestLimit = 5, int timeoutInSeconds = 10)
{
RequestLimit = requestLimit;
_timeoutInSeconds = timeoutInSeconds;
_key = key;
} public bool RequestShouldBeThrottled()
{
ThrottleInfo throttleInfo = _cache.ContainsKey(_key) ? _cache[_key] : null; if (throttleInfo == null || throttleInfo.ExpiresAt <= DateTime.Now)
{
throttleInfo = new ThrottleInfo {
ExpiresAt = DateTime.Now.AddSeconds(_timeoutInSeconds),
RequestCount = 0};
};
WindowResetDate = throttleInfo.ExpiresAt;
throttleInfo.RequestCount++;
_cache[ThrottleGroup] = throttleInfo;
RequestsRemaining = Math.Max(RequestLimit - throttleInfo.RequestCount, 0); return (throttleInfo.RequestCount > RequestLimit);
} private class ThrottleInfo
{
public DateTime ExpiresAt { get; set; } public int RequestCount { get; set; }
}
}创建一个属性
using System;using System.Net;using System.Net.Http;using System.Runtime.CompilerServices;using System.Web;using System.Web.Http.Controllers;using System.Web.Http.Filters;namespace Throttling
{ public class ThrottleFilter : ActionFilterAttribute
{ private Throttler _throttler; private string _throttleGroup; public ThrottleFilter( int RequestLimit = 5, int TimeoutInSeconds = 10,
[CallerMemberName] string ThrottleGroup = null)
{
_throttleGroup = ThrottleGroup;
_throttler = new Throttler(ThrottleGroup, RequestLimit, TimeoutInSeconds);
} public override void OnActionExecuting(HttpActionContext actionContext)
{
setIdentityAsThrottleGroup(); if (_throttler.RequestShouldBeThrottled)
{
actionContext.Response = actionContext.Request.CreateResponse(
(HttpStatusCode)429, "Too many requests");
addThrottleHeaders(actionContext.Response);
}
base.OnActionExecuting(actionContext);
} public override void OnActionExecuted(HttpActionExecutedContext actionExecutedContext)
{
setIdentityAsThrottleGroup(); if (actionExecutedContext.Exception == null) _throttler.IncrementRequestCount();
addThrottleHeaders(actionExecutedContext.Response);
base.OnActionExecuted(actionExecutedContext);
} private void setIdentityAsThrottleGroup()
{ if (_throttleGroup == "identity")
_throttler.ThrottleGroup = HttpContext.Current.User.Identity.Name; if (_throttleGroup == "ipaddress")
_throttler.ThrottleGroup = HttpContext.Current.Request.UserHostAddress;
} private void addThrottleHeaders(HttpResponseMessage response)
{ if (response == null) return;
foreach (var header in _throttler.GetRateLimitHeaders())
response.Headers.Add(header.Key, header.Value);
}
}
}对应的 Throttler代码
using System;using System.Collections.Concurrent;using System.Collections.Generic;namespace Throttling
{ public class Throttler
{
public int RequestLimit { get; private set; } public int RequestsRemaining { get; private set; } public DateTime WindowResetDate { get; private set; } private static ConcurrentDictionary<string, ThrottleInfo> _cache = new ConcurrentDictionary<string, ThrottleInfo>(); public string ThrottleGroup { get; set; } private int _timeoutInSeconds; public Throttler(string key, int requestLimit = 5, int timeoutInSeconds = 10)
{
RequestLimit = requestLimit;
_timeoutInSeconds = timeoutInSeconds;
ThrottleGroup = key;
} private ThrottleInfo getThrottleInfoFromCache()
{
ThrottleInfo throttleInfo =
_cache.ContainsKey(ThrottleGroup) ? _cache[ThrottleGroup] : null; if (throttleInfo == null || throttleInfo.ExpiresAt <= DateTime.Now)
{
throttleInfo = new ThrottleInfo
{
ExpiresAt = DateTime.Now.AddSeconds(_timeoutInSeconds),
RequestCount = 0
};
}; return throttleInfo;
} public bool RequestShouldBeThrottled
{
get
{
ThrottleInfo throttleInfo = getThrottleInfoFromCache();
WindowResetDate = throttleInfo.ExpiresAt;
RequestsRemaining = Math.Max(RequestLimit - throttleInfo.RequestCount, 0); return (throttleInfo.RequestCount > RequestLimit);
}
} public void IncrementRequestCount()
{
ThrottleInfo throttleInfo = getThrottleInfoFromCache();
throttleInfo.RequestCount++;
_cache[ThrottleGroup] = throttleInfo;
} private class ThrottleInfo
{
public DateTime ExpiresAt { get; set; } public int RequestCount { get; set; }
} public Dictionary<string,string> GetRateLimitHeaders()
{
ThrottleInfo throttleInfo = getThrottleInfoFromCache(); int requestsRemaining = Math.Max(RequestLimit - throttleInfo.RequestCount, 0);
var headers = new Dictionary<string,string>();
headers.Add("X-RateLimit-Limit", RequestLimit.ToString());
headers.Add("X-RateLimit-Remaining", RequestsRemaining.ToString());
headers.Add("X-RateLimit-Reset", toUnixTime(throttleInfo.ExpiresAt).ToString()); return headers;
} private long toUnixTime(DateTime date)
{
var epoch = new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc); return Convert.ToInt64((date.ToUniversalTime() - epoch).TotalSeconds);
}
}
}如何使用
基本使用
[ThrottleFilter()]
[HttpGet]
[Route("~/api/helloworld")]public HttpResponseMessage HelloWorld(){ return Request.CreateResponse(HttpStatusCode.OK, "Hello World");
}添加限制
[ThrottleFilter(RequestLimit: 50, TimeoutInSeconds: 5)]
[HttpGet]
[Route("~/api/allow-more")]public HttpResponseMessage HelloWorld2(){ return Request.CreateResponse(HttpStatusCode.OK, "Hello World2");
}使用IP地址
[ThrottleFilter(ThrottleGroup: "ipaddress")]
[HttpGet]
[Route("~/api/name")]public HttpResponseMessage GetName(int id){ return Request.CreateResponse(HttpStatusCode.OK, "John Smith");
}使用user Id
[ThrottleFilter(ThrottleGroup: "identity")]
[HttpGet]
[Route("~/api/name")]public HttpResponseMessage GetName(int id){ return Request.CreateResponse(HttpStatusCode.OK, "Jane Doe");
}
作者：CoderMiner
链接：https://www.jianshu.com/p/56a03c4b71f4
點擊查看更多內容
為 TA 點贊
評論
評論
共同學習，寫下你的評論
評論加載中...
作者其他優質文章
正在加載中
感謝您的支持，我會繼續努力的～
掃碼打賞，你說多少就多少
贊賞金額會直接到老師賬戶
支付方式
打開微信掃一掃，即可進行掃碼打賞哦