Polly的Policy.TimeoutAsync在异步上下文中不适用于PolicyWrap [英] Polly's Policy.TimeoutAsync does not work with PolicyWrap in an async context
问题描述
这是一个完整的示例(将其复制/粘贴并播放,只需获取Polly Nuget)
This is a FULLY working example (Copy/paste it and play around, just get the Polly Nuget)
我有以下控制台应用程序代码,该代码对" http://ptsv2.com/t/v98pb-1521637251/post "(您可以访问此链接"
I have the following Console app code which makes a POST request to an HTTP client sandbox on 'http://ptsv2.com/t/v98pb-1521637251/post' (you can visit this link "http://ptsv2.com/t/v98pb-1521637251" to see the configuration or make yourself a "toilet"):
class Program
{
private static readonly HttpClient _httpClient = new HttpClient()
; //WHY? BECAUSE - https://aspnetmonsters.com/2016/08/2016-08-27-httpclientwrong/
static void Main(string[] args)
{
_httpClient.BaseAddress = new Uri(@"http://ptsv2.com/t/v98pb-1521637251/post");
_httpClient.DefaultRequestHeaders.Accept.Clear();
_httpClient.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("text/xml"));
var result = ExecuteAsync("Test").Result;
Console.WriteLine(result);
Console.ReadLine();
}
private static async Task<string> ExecuteAsync(string request)
{
var response = await Policies.PolicyWrap.ExecuteAsync(async () => await _httpClient.PostAsync("", new StringContent(request)).ConfigureAwait(false));
if (!response.IsSuccessStatusCode)
return "Unsuccessful";
return await response.Content.ReadAsStringAsync().ConfigureAwait(false);
}
}
Http客户端等待4秒钟,然后返回响应.
The Http client waits for 4 seconds, then returns the response.
我已经这样设置了我的政策(超时政策已设置为等待1秒钟才能得到响应):
I have set up my Policies like this (timeout policy is set up to wait for 1 second for the response):
public static class Policies
{
public static TimeoutPolicy<HttpResponseMessage> TimeoutPolicy
{
get
{
return Policy.TimeoutAsync<HttpResponseMessage>(1, onTimeoutAsync: (context, timeSpan, task) =>
{
Console.WriteLine("Timeout delegate fired after " + timeSpan.TotalMilliseconds);
return Task.CompletedTask;
});
}
}
public static RetryPolicy<HttpResponseMessage> RetryPolicy
{
get
{
return Policy.HandleResult<HttpResponseMessage>(r => !r.IsSuccessStatusCode)
.Or<TimeoutRejectedException>()
.RetryAsync(3, onRetryAsync: (delegateResult, i) =>
{
Console.WriteLine("Retry delegate fired for time No. " + i);
return Task.CompletedTask;
});
}
}
public static FallbackPolicy<HttpResponseMessage> FallbackPolicy
{
get
{
return Policy.HandleResult<HttpResponseMessage>(r => !r.IsSuccessStatusCode)
.Or<TimeoutRejectedException>()
.FallbackAsync(new HttpResponseMessage(HttpStatusCode.InternalServerError), onFallbackAsync: (delegateResult, context) =>
{
Console.WriteLine("Fallback delegate fired");
return Task.CompletedTask;
});
}
}
public static PolicyWrap<HttpResponseMessage> PolicyWrap
{
get
{
return Policy.WrapAsync(FallbackPolicy, RetryPolicy, TimeoutPolicy);
}
}
}
但是,根本没有按下onTimeoutAsync委托,控制台会打印出以下内容:
However, onTimeoutAsync delegate is not being hit at all and the console prints out the following:
Retry delegate fired for time No. 1 //Hit after 4 seconds
Retry delegate fired for time No. 2 //Hit after 4 more seconds
Retry delegate fired for time No. 3 //Hit after 4 more seconds
Fallback delegate fired
Unsuccessful
它包含在PolicyWrap中并且是异步的,我不知道为什么它没有被点击. 任何信息都将受到高度赞赏.
It is included in the PolicyWrap and is Async and I do not know why it is not being hit. Any information is highly appreciated.
推荐答案
Polly 超时政策(默认值为TimeoutStrategy.Optimistic
)通过超时CancellationToken
进行操作,因此您执行的委托必须响应 Polly Timeout Wiki .
Polly Timeout policy with the default TimeoutStrategy.Optimistic
operates by timing-out CancellationToken
, so the delegates you execute must respond to co-operative cancellation. See the Polly Timeout wiki for more detail.
将执行行更改为以下内容应使超时起作用:
Changing your execution line to the following should make the timeout work:
var response = await Policies.PolicyWrap.ExecuteAsync(
async ct => await _httpClient.PostAsync(/* uri */, new StringContent(request), ct).ConfigureAwait(false),
CancellationToken.None // CancellationToken.None here indicates you have no independent cancellation control you wish to add to the cancellation provided by TimeoutPolicy. You can also pass in your own independent CancellationToken.
);
默认情况下, Polly异步执行不会在捕获的同步上下文上继续(它们会执行使用.ConfigureAwait(false)
),因此也可以缩短为:
Polly async executions by default do not continue on captured synchronization context (they execute with .ConfigureAwait(false)
), so this can also be shortened to:
var response = await Policies.PolicyWrap.ExecuteAsync(
ct => _httpClient.PostAsync(/* uri */, new StringContent(request), ct),
CancellationToken.None
);
这篇关于Polly的Policy.TimeoutAsync在异步上下文中不适用于PolicyWrap的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!