正确使用 IHttpClientFactory 进行 .net-core 瞬态服务

Question

我正在考虑使用 IHttpClientFactory 在我的 asp.net 核心应用程序中调用外部 API。我见过几个例子，其中客户端工厂是在服务 class 的构造函数中创建的。然后那个 class 的方法调用那个客户端工厂来生成一个 HttpClient 的实例来发出 Http 请求。像下面的示例代码：

public class MyTransientService: IMyService
{
    private readonly IHttpClientFactory _clientFactory;

    public MyTransientService(
        IHttpClientFactory clientFactory
    )
    {
        _clientFactory = clientFactory;
    }

    public async Task<MyData> GetData()
    {
        //construct the request
        var httpClient = _clientFactory.CreateClient();
        var response = await client.SendAsync(request);
        ...
    }
}

如果服务在startup.cs中被注册为transient，每次调用服务时是否都会生成一个新的HttpClientFactory实例？每个请求一个新的 HttpClientFactory？那么下面的方法不是更有效地使用工厂吗？

public class MyTransientService: IMyService
    {
        private readonly HttpClient _client;
    
        public MyTransientService(
            HtpClient client
        )
        {
            _client = client;
        }
    
        public async Task<MyData> GetData()
        {
            Uri uri = new Uri(StaticUtils.AddQueryString(url, props));
            var response = await _client.SendAsync(request);
            ...
        }
    }

Answer 1

我会考虑自己创建 HttpClient 的坏习惯，您可以自行控制创建的数量。如果 MyTransientService 是瞬态的，您将最终创建大量套接字连接（每个 instance/request 一个）创建 HttpClient 以供重用。

查看类型化客户端：https://docs.microsoft.com/en-us/dotnet/architecture/microservices/implement-resilient-applications/use-httpclientfactory-to-implement-resilient-http-requests

public void ConfigureServices(IServiceCollection services)
{
    services.AddHttpClient("hello", c =>
    {
        c.BaseAddress = new Uri("http://localhost:5000");
    })
    .AddTypedClient<MyTransientService>();

    services.AddControllers();
}

public class MyTransientService: IMyService
{
    private readonly HttpClient _client;

    public MyTransientService(
        HtpClient client
    )
    {
        _client = client;
    }

    public async Task<MyData> GetData()
    {
        Uri uri = new Uri(StaticUtils.AddQueryString(url, props));
        var response = await _client.SendAsync(request);
        ...
    }
}

正确使用 IHttpClientFactory 进行 .net-core 瞬态服务

Correct usage of IHttpClientFactory for a .net-core transient service

c#

dotnet-httpclient

asp.net-core