Question

我正在尝试使用新的.NET Core 2.1 HttpClientFactory来实现Polly Timeout策略；但是，我似乎无法使超时发生。

我的ConfigureServices：

// Configure polly policies
TimeoutPolicy<HttpResponseMessage> timeoutPolicy = Policy.TimeoutAsync<HttpResponseMessage>(5, TimeoutStrategy.Pessimistic);

// Configure platform service clients
services.AddHttpClient<IDiscoveryClient, DiscoveryClient>()
    .AddPolicyHandler(timeoutPolicy);

我在DiscoveryClient中的POST方法：

public async Task<TResponse> PostXMLAsync<TResponse, TPostData>(string url, TPostData postData)
    where TResponse : ClientResponse
    where TPostData : ClientPostData
{
    HttpResponseMessage response = await httpClient.PostAsXmlAsync(url, postData);
    response.EnsureSuccessStatusCode();
    return await response.Content.ReadAsAsync<TResponse>();
}

不幸的是，该呼叫在默认的100s之后超时，而不是在Polly策略中定义的5s之后超时。

对我在做什么错有任何想法吗？

Answer 1

首先让我们定义一个模拟服务器，它在 100 秒后响应 500：

const string address = "http://localhost:9000";
var delay = TimeSpan.FromSeconds(100);
var server = WireMockServer.Start(new WireMockServerSettings { Urls = new[] { address } });
server
    .Given(Request.Create().WithPath("/").UsingPost())
    .RespondWith(Response.Create().WithDelay(delay).WithStatusCode(500));

为此我使用了 WireMock.Net。

现在，让我们看看 IDiscoveryClient 和 DiscoveryClient：

interface IDiscoveryClient
{
    Task<TResponse> SendRequest<TResponse, TPostData>(string url, TPostData data);
}

class DiscoveryClient : IDiscoveryClient
{
    private readonly HttpClient httpClient;

    public DiscoveryClient(HttpClient httpClient) => this.httpClient = httpClient;

    public async Task<TResponse> SendRequest<TResponse, TPostData>(string url, TPostData data)
    {
        var content = new StringContent(JsonConvert.SerializeObject(data), Encoding.UTF8);
        var response = await httpClient.PostAsync(url, content);
        response.EnsureSuccessStatusCode();
        var rawData = await response.Content.ReadAsStringAsync();
        return JsonConvert.DeserializeObject<TResponse>(rawData);
    }
}

class TestRequest { public string Content { get; set; } }
class TestResponse { public string Data { get; set; } }

我使用了 json 而不是 xml，但这从问题的角度来看并不重要。

最后让我们连接 DI 并发出请求：

AsyncTimeoutPolicy<HttpResponseMessage> timeoutPolicy =
    Policy.TimeoutAsync<HttpResponseMessage>(5, TimeoutStrategy.Pessimistic);

IServiceCollection services = new ServiceCollection();
services.AddHttpClient<IDiscoveryClient, DiscoveryClient>()
    .AddPolicyHandler(timeoutPolicy);

ServiceProvider serviceProvider = services.BuildServiceProvider();
var client = serviceProvider.GetService<IDiscoveryClient>();

Stopwatch sw = Stopwatch.StartNew();
try
{
    TestResponse res = await client.SendRequest<TestResponse, TestRequest>(address, new TestRequest { Content =  "Test"});
}
catch (TimeoutRejectedException ex)
{
    sw.Stop();
    Console.WriteLine(sw.Elapsed);
}

打印输出将是这样的：

00:00:05.0296804

好消息是它也适用于 Optimistic 和 Pessimistic 策略。

具有Polly超时策略的HttpClientFactory似乎不起作用

1 个答案: