是否应该处理由 HttpClientFactory 创建的 HttpClient 实例? [英] Should HttpClient instances created by HttpClientFactory be disposed?

问题描述

因此，我在 Startup.cs 中使用服务集合注册了一个命名客户端:

So, I've registered a named client with the services collection in my Startup.cs:

services.AddHttpClient(someServiceName, 
                       client => client.BaseAddress = baseAddress);

现在可以从我的服务提供商处注入一个 IHttpClientFactory.

and now can inject an IHttpClientFactory from my service provider.

使用这个 IHttpClientFactory，我想出了一个客户端实例:

Using this IHttpClientFactory, I conjure up a client instance:

var client = httpClientFactory.CreateClient(someServiceName)

曾几何时，在处理 HttpClient 实例时需要非常小心，因为它是 很少做正确的事情.

Once upon a time, it was necessary to be very careful about the disposing of HttpClient instances, as it was rarely the right thing to do.

但是，现在我们有了HttpClientFactory，这还重要吗?这个 client 是否应该/可以放心地处理?例如

However, now we have HttpClientFactory, does this matter any more? Should/Can this client be disposed without worry? e.g.

using (var httpClient = httpClientFactory.CreateClient(someServiceName))
using (var response = await httpClient.PostAsync(somePath, someData))
{
    var content = await response.Content.ReadAsAsync<SomeResponse>();
    //...
}

推荐答案

调用 Dispose 方法不是必需的，但如果出于某些原因，您仍然可以调用它.

Calling the Dispose method is not required but you can still call it if you need for some reasons.

证明:HttpClient 和生命周期管理

不需要处理客户端.Disposal 取消传出请求并保证在调用 Dispose 后不能使用给定的 HttpClient 实例.IHttpClientFactory 跟踪和处理 HttpClient 实例使用的资源.HttpClient 实例通常可以被视为不需要处理的 .NET 对象.

Disposal of the client isn't required. Disposal cancels outgoing requests and guarantees the given HttpClient instance can't be used after calling Dispose. IHttpClientFactory tracks and disposes resources used by HttpClient instances. The HttpClient instances can generally be treated as .NET objects not requiring disposal.

检查 DefaultHttpClientFactory 的来源:

public HttpClient CreateClient(string name)
{
    if (name == null)
    {
        throw new ArgumentNullException(nameof(name));
    }

    var handler = CreateHandler(name);
    var client = new HttpClient(handler, disposeHandler: false);

    var options = _optionsMonitor.Get(name);
    for (var i = 0; i < options.HttpClientActions.Count; i++)
    {
        options.HttpClientActions[i](client);
    }

    return client;
}

HttpMessageHandler 的实例存储了 HttpClient 的非托管资源.在经典场景中，HttpClient 创建 HttpMessageHandler 的实例并在自己处理的同时处理它.

The instance of HttpMessageHandler stores unmanaged resources of the HttpClient. In the classical scenario the HttpClient creates the instance of HttpMessageHandler and disposes it while itself disposing.

在上面的代码中可以看到，HttpClient的不同实例共享了HttpMessageHandler的单个实例，并没有对其进行处理(disposeHandler:false>).

You can see in the above code that different instances of HttpClient shares single instance of HttpMessageHandler and doesn't dispose it (disposeHandler: false).

所以，HttpClient.Dispose 的调用什么都不做.但这并不危险.

So, the call of the HttpClient.Dispose does nothing. But it's not dangerous.

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