C#中間件如何管理API限流規則

在C#中，我們可以使用ASP.NET Core的中間件來實現API限流。這里是一個簡單的示例，展示了如何創建一個自定義中間件來管理API限流規則：

1. 首先，安裝以下NuGet包：

   • Microsoft.AspNetCore.Http
   • Microsoft.Extensions.DependencyInjection
   • Microsoft.Extensions.Options

2. 創建一個名為RateLimitingOptions的類，用于存儲限流選項：

public class RateLimitingOptions
{
    public int MaxRequestsPerMinute { get; set; } = 60;
}

3. 創建一個名為RateLimiterMiddleware的類，實現自定義中間件：

using System;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.Options;

public class RateLimiterMiddleware
{
    private readonly RequestDelegate _next;
    private readonly RateLimitingOptions _options;

    public RateLimiterMiddleware(RequestDelegate next, IOptions<RateLimitingOptions> options)
    {
        _next = next;
        _options = options.Value;
    }

    public async Task Invoke(HttpContext context)
    {
        var clientId = context.Connection.RemoteIpAddress.ToString();
        var rateLimitKey = $"RateLimit:{clientId}";

        // 獲取當前請求計數
        var currentRequestCount = context.Items.ContainsKey(rateLimitKey) ? (int)context.Items[rateLimitKey] : 0;

        if (currentRequestCount >= _options.MaxRequestsPerMinute)
        {
            // 超過限制，返回429狀態碼
            context.Response.StatusCode = 429;
            await context.Response.WriteAsync("Too Many Requests");
            return;
        }

        // 更新請求計數
        context.Items[rateLimitKey] = currentRequestCount + 1;

        // 調用下一個中間件
        await _next.Invoke(context);
    }
}

4. 在Startup.cs中注冊中間件：

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;

public class Startup
{
    public Startup(IConfiguration configuration)
    {
        Configuration = configuration;
    }

    public IConfiguration Configuration { get; }

    public void ConfigureServices(IServiceCollection services)
    {
        services.Configure<RateLimitingOptions>(Configuration.GetSection("RateLimiting"));
        services.AddControllers();
    }

    public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
    {
        if (env.IsDevelopment())
        {
            app.UseDeveloperExceptionPage();
        }

        app.UseHttpsRedirection();

        app.UseRouting();

        app.UseAuthorization();

        app.UseMiddleware<RateLimiterMiddleware>();

        app.UseEndpoints(endpoints =>
        {
            endpoints.MapControllers();
        });
    }
}

5. 在appsettings.json中配置限流選項：

{
  "RateLimiting": {
    "MaxRequestsPerMinute": 10
  }
}

現在，你已經創建了一個自定義中間件來管理API限流規則。你可以根據需要調整限流選項，例如限制每分鐘的請求數或者為不同的客戶端設置不同的限制。