using System.Net.Http;
using System.Net.Http.Headers;
public static class HttpClientFactory
{
    private static readonly HttpClient _sharedClient;
    static HttpClientFactory()
    {
        // 配置 SocketsHttpHandler 管理連接池
        var socketHandler = new SocketsHttpHandler
        {
            // 關(guān)鍵配置：限制連接生命周期，建議 2-15 分鐘
            PooledConnectionLifetime = TimeSpan.FromMinutes(5),
            // 可選：設(shè)置空閑連接超時時間
            PooledConnectionIdleTimeout = TimeSpan.FromMinutes(2),
            // 可選：禁用自動重定向
            AllowAutoRedirect = false
        };
        _sharedClient = new HttpClient(socketHandler)
        {
            // 設(shè)置基礎(chǔ)地址，簡化后續(xù)請求 URL
            BaseAddress = new Uri("https://api.example.com"),
            // 設(shè)置默認(rèn)請求超時
            Timeout = TimeSpan.FromSeconds(30)
        };
        // 配置默認(rèn)請求頭
        _sharedClient.DefaultRequestHeaders.Accept.Add(
            new MediaTypeWithQualityHeaderValue("application/json"));
    }
    public static HttpClient SharedClient => _sharedClient;
}

// Program.cs
using Microsoft.Extensions.DependencyInjection;
using System.Net.Http;
var builder = WebApplication.CreateBuilder(args);
// 方式 1：注冊命名客戶端
builder.Services.AddHttpClient("JsonPlaceholderClient", client =>
{
    client.BaseAddress = new Uri("https://jsonplaceholder.typicode.com");
    client.Timeout = TimeSpan.FromSeconds(10);
    client.DefaultRequestHeaders.Add("Accept", "application/json");
});
// 方式 2：注冊類型化客戶端（推薦）
builder.Services.AddHttpClient<ITodoService, TodoService>(client =>
{
    client.BaseAddress = new Uri("https://jsonplaceholder.typicode.com");
})
// 添加彈性策略
.AddPolicyHandler(GetRetryPolicy());
var app = builder.Build();
// ...

// 命名客戶端使用方式
public class TodoController : ControllerBase
{
    private readonly IHttpClientFactory _clientFactory;
    public TodoController(IHttpClientFactory clientFactory)
    {
        _clientFactory = clientFactory;
    }
    [HttpGet]
    public async Task<IActionResult> GetTodos()
    {
        var client = _clientFactory.CreateClient("JsonPlaceholderClient");
        var response = await client.GetAsync("todos");
        // ...
    }
}
// 類型化客戶端使用方式（更簡潔）
public class TodoService : ITodoService
{
    private readonly HttpClient _httpClient;
    public TodoService(HttpClient httpClient)
    {
        _httpClient = httpClient;
    }
    public async Task<List<Todo>> GetTodosAsync()
    {
        var response = await _httpClient.GetFromJsonAsync<List<Todo>>("todos");
        // ...
    }
}

using System.Net.Http;
using Microsoft.Extensions.Http.Resilience;
using Polly;
using Polly.Retry;
public static class ResilientHttpClientFactory
{
    private static readonly HttpClient _resilientClient;
    static ResilientHttpClientFactory()
    {
        // 1. 創(chuàng)建重試策略
        var retryPipeline = new ResiliencePipelineBuilder<HttpResponseMessage>()
            .AddRetry(new HttpRetryStrategyOptions
            {
                BackoffType = DelayBackoffType.Exponential, // 指數(shù)退避
                MaxRetryAttempts = 3, // 最大重試次數(shù)
                UseJitter = true, // 啟用抖動，避免請求風(fēng)暴
                ShouldHandle = new PredicateBuilder<HttpResponseMessage>()
                    .HandleTransientHttpError() // 處理常見 transient 錯誤
                    .Handle<HttpRequestException>()
            })
            .Build();
        // 2. 配置連接池
        var socketHandler = new SocketsHttpHandler
        {
            PooledConnectionLifetime = TimeSpan.FromMinutes(10),
            PooledConnectionIdleTimeout = TimeSpan.FromMinutes(3)
        };
        // 3. 創(chuàng)建彈性處理程序
        var resilienceHandler = new ResilienceHandler(retryPipeline)
        {
            InnerHandler = socketHandler
        };
        // 4. 構(gòu)建 HttpClient
        _resilientClient = new HttpClient(resilienceHandler)
        {
            BaseAddress = new Uri("https://api.example.com"),
            Timeout = TimeSpan.FromSeconds(30)
        };
    }
    public static HttpClient ResilientClient => _resilientClient;
}

<PackageReference Include="Microsoft.Extensions.Http.Resilience" Version="8.0.0" />