C# Polly断路器策略和带有ASP.NET核心API的HttpClient
我在结合C# Polly断路器策略和带有ASP.NET核心API的HttpClient,c#,asp.net-core,.net-core,asp.net-core-webapi,polly,C#,Asp.net Core,.net Core,Asp.net Core Webapi,Polly,我在结合HttpClient设置Polly的断路器时遇到问题 具体而言,断路器和HttpClient用于ASP.NET核心Web API控制器,链接如下: 下面是我想要的 重试策略:如果出现暂时性错误,则对每个请求重试3次 电路断路器策略:如果所有请求中出现五个瞬时错误,则生效 问题 尽管重试策略正常工作,但断路器策略不工作 CarController在发生5次来自_httpClient.SendAsync()的异常后仍然接收请求,并且不会暂停30秒(请求由控制器立即处理) 重新分解前已
HttpClient
设置Polly的断路器时遇到问题
具体而言,断路器
和HttpClient
用于ASP.NET核心Web API控制器,链接如下:
下面是我想要的
- 重试策略:如果出现暂时性错误,则对每个请求重试3次
- 电路断路器策略:如果所有请求中出现五个瞬时错误,则生效
HttpClientService
public void ConfigureServices(IServiceCollection services)
{
services.AddHttpClient();
services.AddHttpClient<IHttpClientService, HttpClientService>()
.AddPolicyHandler((service, request) =>
HttpPolicyExtensions.HandleTransientHttpError()
.WaitAndRetryAsync(3,
retryCount => TimeSpan.FromSeconds(Math.Pow(2, retryCount)),
onRetry: (outcome, timespan, retryCount, context) =>
{
service.GetService<ILog>().Error("Delaying for {delay}ms, then making retry {retry}.",
timespan.TotalMilliseconds, retryCount);
}
)
)
)
.AddPolicyHandler((service, request) =>
HttpPolicyExtensions.HandleTransientHttpError()
//Further external requests are blocked for 30 seconds if five failed attempts occur sequentially.
//Circuit breaker policies are stateful.All calls through this client share the same circuit state.
.CircuitBreakerAsync(5,
TimeSpan.FromSeconds(30),
(result, timeSpan, context)=>
service.GetService<ILog>().Error("CircuitBreaker onBreak for {delay}ms", timeSpan.TotalMilliseconds),
context =>
service.GetService<ILog>().Error("CircuitBreaker onReset")));
}
HttpClientService
HttpClient在请求之间似乎不是有状态的
断路器不工作:即使在发生来自\u httpClient.SendAsync()
的五个瞬态错误(例如HttpRequestException
)后,CarController仍然可以接收请求,并且不会暂停30秒
[ApiVersion("1")]
[Route("api/v{version:apiVersion}/[controller]")]
[ApiController]
public class CarController : ControllerBase
{
private readonly ILog _logger;
private readonly IHttpClientService _httpClientService;
private readonly IOptions<Config> _config;
public CarController(ILog logger, IHttpClientService httpClientService, IOptions<Config> config)
{
_logger = logger;
_httpClientService = httpClientService;
_config = config;
}
[HttpPost]
public async Task<ActionResult> Post()
{
using (StreamReader reader = new StreamReader(Request.Body, Encoding.UTF8))
{
string body = reader.ReadToEnd();
var statusCode = await _httpClientService.PostAsync(
"url",
new Dictionary<string, string>
{
{"headerID", "Id"}
},
body);
return StatusCode((int)statusCode);
}
}
}
public class HttpClientService
{
private readonly HttpClient _httpClient;
public HttpClientService(HttpClient client)
{
_httpClient = client;
}
public async Task<HttpStatusCode> PostAsync(string url, Dictionary<string, string> headers, string body)
{
using (var content = new StringContent(body, Encoding.UTF8, "application/json"))
{
foreach (var keyValue in headers)
{
content.Headers.Add(keyValue.Key, keyValue.Value);
}
var request = new HttpRequestMessage(HttpMethod.Post, url)
{
Content = content
};
var response = await _httpClient.SendAsync(request);
response.EnsureSuccessStatusCode();
return response.StatusCode;
}
}
公共类HttpClientService
{
私有只读HttpClientu HttpClient;
公共HttpClientService(HttpClient客户端)
{
_httpClient=client;
}
公共异步任务PostAsync(字符串url、字典头、字符串正文)
{
使用(var content=newstringcontent(body,Encoding.UTF8,“application/json”))
{
foreach(标头中的var keyValue)
{
content.Headers.Add(keyValue.Key,keyValue.Value);
}
var request=newhttprequestmessage(HttpMethod.Post,url)
{
内容=内容
};
var response=await\u httpClient.sendsync(请求);
response.EnsureSuccessStatusCode();
返回response.StatusCode;
}
}
ASP.NET核心API 2.2
更新
更新了SetWaitAndRetryPolicy扩展方法以使用IServiceProvider。断路器策略是,因此需要 发布代码中HttpClientFactory上的重载的使用方式:
.AddPolicyHandler((service, request) => HttpPolicyExtensions.HandleTransientHttpError()
.CircuitBreakerAsync( /* etc */
是的,因此断路器从来没有时间建立故障状态
重载(和类似的)是。但事实上,发布的代码(编辑:最初发布的代码是)没有使用服务,请求输入参数,因此您可以删除(服务,请求)=>
部分,并使用HttpClientFactory上的重载,该重载采用策略实例:
.AddPolicyHandler(HttpPolicyExtensions.HandleTransientHttpError()
.WaitAndRetryAsync(/* etc */))
.AddPolicyHandler(HttpPolicyExtensions.HandleTransientHttpError()
.CircuitBreakerAsync(/* etc */))
HttpPolicyExtensions.HandletTransientHttpError().CircuitBreakerAsync(/*etc*/)
返回的断路器的单个长期实例将由HttpClient实例使用,HttpClientFactory配置为使用该实例
旁注(特别是对于任何想要使用给定过载的断路器的读者):
可以在HttpClientFactory中将断路器与请求驱动的policySelector
重载一起使用。只需确保lambda表达式选择单个实例,而不是每次请求都生成一个新实例。例如:
var circuitBreaker = HttpPolicyExtensions.HandleTransientHttpError().CircuitBreakerAsync(/* etc */);
services.AddHttpClient<IHttpClientService, HttpClientService>()
.AddPolicyHandler((service, request) => circuitBreaker); // By way of example technique: more typically with this overload, there is some more complex logic to select different policies for different kinds of request.
var-circuitBreaker=HttpPolicyExtensions.HandleTransientHttpError().CircuitBreakerAsync(/*etc*/);
services.AddHttpClient()
.AddPolicyHandler((服务,请求)=>断路器);//通过示例技术:更典型的是,对于这种重载,有一些更复杂的逻辑来为不同类型的请求选择不同的策略。
编辑以回答注释中的问题:该实例不必声明为static
,即可使其长期存在。它可以在Startup.ConfigureServices(…)中声明
方法,在使用前立即使用,如上面的代码示例所示。lambda和在HttpClientFactory上配置它将捕获它并使其长寿
断路器
实例应为。如果您将断路器连接到通过HttpClientFactory声明的特定HttpClient
配置,则通过该HttpClient
配置实例的所有调用(稍后由DI从HttpClientFactory检索)将共享断路器,从而断开通信n
将断路器与HttpClientFactory一起使用时,这通常意味着您可以在HttpClientFactory上为每个子系统声明一个HttpClient
配置(键入或命名),您希望对其调用断路器
旁注:还选择了断路器的变型。(仅在额外因素的情况下提及;发布的问题涉及请求之间发生的5个错误,但不是连续发生的。)我猜问题是因为您调用了两次AddHttpClient
,但您没有与它共享断路策略(也不是waitandertryAsync
)。我不太确定您创建IHttpClientService
的方式。您不应该在注册时为其设置基址吗?还要注意:当您达到异常限制时(在您的情况下为3),状态机将移动到打开
状态。但这不会阻止您的控制器被调用。控制器本身可以被调用,但Http
调用将快速失败,出现brokencircuiiteexception
,并将在30天内保持这种状态