c# - 从 Azure 中托管的 Asp.net Core MVC Web 应用程序获取 "Response status code does not indicate success: 502 (Bad Gateway)"

Question

我有一个基于 Asp.net core MVC (V 1.1.1) 构建的客户端应用程序和一个基于 Asp.net core (v 2.1) 构建的 Web API。我已将两者托管在 Azure 上。

在发出一些请求时，网络应用程序失败并给出 502 Bad Gateway 响应。

Response status code does not indicate success: 502 (Bad Gateway).

The specified CGI application encountered an error and the server terminated the process.

此问题是间歇性的，但是，当请求的处理时间超过 2 分钟时，似乎会发生此问题。我已在 Web.config 文件中的客户端和 API 端将 requestTimeout 设置为 20 分钟，但仍然没有解决。有时，相同的请求在更短的时间内得到处理，并且我得到了响应。

此外，Httpclient 也设置了 5 分钟超时，但没有成功。

<aspNetCore requestTimeout="00:20:00"/>

_httpClient.Timeout = new TimeSpan(0, 5, 0);

我已经在本地测试了该应用程序，无法面对这个问题，即使处理时间超过 3 分钟也能得到响应。

如果请求超过 2 分钟，Azure Web 应用程序似乎不会等待处理请求。但是， azure session 超时指定为 230 秒(3.8 分钟)，但它仍然没有等待，并且应用程序不会将此情况视为错误，也不会记录任何内容。

客户端代码:

public class ApiClientFactory
{
    private static Uri ApiUrl;
    private static Lazy<ApiClient> restClient = new Lazy<ApiClient>(
        () => new ApiClient(ApiUrl),
        LazyThreadSafetyMode.ExecutionAndPublication);

    static ApiClientFactory()
    {
        ApiUrl = new Uri(Convert.ToString(ConfigurationManager.AppSettings["WebAPIUrl"]));
    }

    public static ApiClient Instance
    {
        get
        {
            return restClient.Value;
        }
    }
}

public class ApiClient
{
   private readonly HttpClient _httpClient;
   private readonly Uri BaseEndPointUrl;

   public ApiClient(Uri baseEndPointUrl)
   {
       if (baseEndPointUrl == null)
           throw new ArgumentNullException("baseEndPointUrl");

       BaseEndPointUrl = baseEndPointUrl;
       _httpClient = new HttpClient();
       _httpClient.DefaultRequestHeaders.Add("Accept", "application/json");
       _httpClient.Timeout = new TimeSpan(0, 5, 0); //Timeout needed for few modules to get results from db.
   }

   private HttpContent CreateHttpContent<T>(T content)
   {
       var json = JsonConvert.SerializeObject(content, MicrosoftDateFormatSettings);
       return new StringContent(json, Encoding.UTF8, "application/json");
   }

   private static JsonSerializerSettings MicrosoftDateFormatSettings
   {
       get
       {
           return new JsonSerializerSettings
           {
               DateFormatHandling = DateFormatHandling.MicrosoftDateFormat
           };
       }
   }

   public async Task<T1> PostAsync<T1, T2>(string url, T2 content, string token)
   {
       try
       {
           _httpClient.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", token);
           var response = await _httpClient.PostAsync(url, CreateHttpContent<T2>(content));

           if (response.StatusCode == HttpStatusCode.InternalServerError){
               var exception = await response.Content.ReadAsStringAsync();
               throw new Exception(exception);
           }
           response.EnsureSuccessStatusCode();
           var data = await response.Content.ReadAsStringAsync();

           return JsonConvert.DeserializeObject<T1>(data);
       }
       catch (Exception ex){throw ex;}
   }
}

请在遇到问题时提供帮助。

Answer 1

您可以实现重试请求的方法，或者简单地使用 .Net Polly对于此类错误。增加超时设置并不是一个好习惯。

方法:

    private async Task<bool> PostAsync()//Params you need
    {
        HttpStatusCode[] httpStatusCodesWorthRetrying =
        {
            HttpStatusCode.RequestTimeout,
            HttpStatusCode.InternalServerError,
            HttpStatusCode.BadGateway,
            HttpStatusCode.ServiceUnavailable,
            HttpStatusCode.GatewayTimeout
        };

        var maxAttempts = 0;

        while (maxAttempts < 3)
        {
            var response =  await _httpClient.PostAsync(requestUrl, CreateHttpContent<T2>(content));
            if (!httpStatusCodesWorthRetrying.Contains(response.StatusCode))
            {
                return true;
            }

            maxAttempts ++;
            await Task.Delay(300);
        }
        return false;
    }

波莉:

    private async Task PostAsync()//Params you need
    {
        HttpStatusCode[] httpStatusCodesWorthRetrying =
        {
            HttpStatusCode.RequestTimeout,
            HttpStatusCode.InternalServerError,
            HttpStatusCode.BadGateway,
            HttpStatusCode.ServiceUnavailable,
            HttpStatusCode.GatewayTimeout
        };


        _retryPolicy = Policy
            .Handle<HttpRequestException>()
            .OrResult<HttpResponseMessage>(r => httpStatusCodesWorthRetrying.Contains(r.StatusCode))
            .WaitAndRetry(4, retryAttempt => TimeSpan.FromSeconds(Math.Pow(2, retryAttempt)));

        _retryPolicy.Execute(await _httpClient.PostAsync(requestUrl, CreateHttpContent<T2>(content)));

    }