ASP.Net Core 2.1和IHttpClientFactory中的Flurl客户端生存期 [英] Flurl client lifetime in ASP.Net Core 2.1 and IHttpClientFactory

问题描述

Flurl指出推荐使用单例客户端模式:

Flurl states that using singleton client is recommended pattern:

HttpClient旨在实例化一次，并在应用程序的整个生命周期内重复使用.特别是在服务器应用程序中，为每个请求创建一个新的HttpClient实例将耗尽繁重负载下可用的套接字数量.这将导致SocketException错误.

HttpClient is intended to be instantiated once and re-used throughout the life of an application. Especially in server applications, creating a new HttpClient instance for every request will exhaust the number of sockets available under heavy loads. This will result in SocketException errors.

但是自从Asp.Net Core 2.1以来， Net中HttpClient生存期的更新规则核心2.1 .

But since Asp.Net Core 2.1 there are updated rules for HttpClient lifetime in Net Core 2.1.

当您使用HttpClientFactory请求HttpClient时，实际上每次都会获得一个新实例，这意味着我们不必担心会改变其状态.该HttpClient可以(也可以不)使用池中现有的HttpClientHandler，因此使用现有的开放连接.

When you use the HttpClientFactory to request a HttpClient, you do in fact get a new instance each time, which means we don’t have to worry about mutating it’s state. This HttpClient may (or may not) use an existing HttpClientHandler from the pool and therefore use an existing open connection.

如何修改Flurl以在后台使用IHttpClientFactory?我应该创建自定义Flurl的settings.HttpClientFactory，然后通过MS IHttpClientFactory创建HttpClient吗?

How to modify Flurl to use IHttpClientFactory under hood? Should I create custom Flurl's settings.HttpClientFactory and there create HttpClient through MS IHttpClientFactory?

推荐答案

首先，应该注意，MS的新HttpClientFactory旨在与ASP.NET Core 2.1及其内置的DI容器结合使用.如果您没有将FlurlClient注入到控制器或服务类中，而是使用Flurl，如下所示:

First, it should be noted that MS's new HttpClientFactory is intended to be used in conjunction with ASP.NET Core 2.1 and its built-in DI container. If you're not injecting FlurlClients into controllers or service classes, and are instead using Flurl like this:

await url.GetJsonAsync();

那么它甚至不相关.您应该不实施 Flurl的IHttpClientFactory 以使用MS.它没有使用DI容器的适当上下文，您最终将诉诸服务位置，这是一种反模式.您想利用的这些新套接字池功能实际上处于较低级别:

then it's not even relevant. You should not implement Flurl's IHttpClientFactory to use MS's. It doesn't have the proper context to use the DI container and you'll end up resorting to service location, which is an anti-pattern. Those new socket pooling features you want to take advantage of actually live at a lower level:System.Net.Http.SocketsHttpHandler. Flurl uses HttpClientHander as its message handler by default, but luckily that's been rewritten in .NET Core 2.1 to defer all of its work to SocketsHttpHandler by default. In other words, if you're using Flurl in a .NET Core 2.1 app, you're already getting all the new socket management goodies that MS has been working on.

如果您正在在ASP.NET Core 2.1应用程序中显式使用FlurlClient，可以替代HttpClient，并希望在利用以下优点的情况下将其注入您的类中: MS的HttpClientFactory所提供的内容，我建议完全按照MS的规定在ConfigureServices中设置HttpClientFactory，并且当您需要FlurlClient实例时，请使用带有HttpClient实例的构造函数.例如，当使用类型化的客户机模式时，您的服务类可能如下所示:

If you are using FlurlClient explicitly in an ASP.NET Core 2.1 app, as sort of a replacement for HttpClient, and would like to inject it into your classes while taking advantage of what MS's HttpClientFactory has to offer, I would suggest setting up HttpClientFactory in ConfigureServices exactly as prescribed by MS, and when you need a FlurlClient instance, use the constructor that takes an HttpClient instance. For example, when using the typed clients pattern, your service class might look like this:

public class MyService
{
    private readonly IFlurlClient _flurlClient;

    public MyService(HttpClient httpClient)
    {
        _flurlClient = new FlurlClient(httpClient);
    }
}

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