ReCAPTCHA 因“现有连接被远程主机强行关闭”错误而失败很多

Question

我在 Azure 云中托管的 MVC4 应用程序中使用 ReCAPTCHA 来创建一个带有一个注册表单的简单网站。目前，我们每小时大约有 100-120 次成功注册。问题是我在日志中有数百个System.Net.Sockets.SocketException: An existing connection was forcibly closed by the remote host 错误，然后数字一直在快速增长：

System.Net.Http.HttpRequestException: An error occurred while sending the request. ---> 
System.Net.WebException: The underlying connection was closed: An unexpected error occurred on a receive. ---> 
System.IO.IOException: Unable to read data from the transport connection: An existing connection was forcibly closed by the remote host. ---> 
System.Net.Sockets.SocketException: An existing connection was forcibly closed by the remote host
at System.Net.Sockets.NetworkStream.EndRead(IAsyncResult asyncResult)     
--- End of inner exception stack trace ---     
at System.Net.Sockets.NetworkStream.EndRead(IAsyncResult asyncResult)     
at System.Net.Connection.ReadCallback(IAsyncResult asyncResult)     
--- End of inner exception stack trace ---     
at System.Net.HttpWebRequest.EndGetResponse(IAsyncResult asyncResult)     
at System.Net.Http.HttpClientHandler.GetResponseCallback(IAsyncResult ar)     
--- End of inner exception stack trace ---     
--- End of inner exception stack trace ---     
at System.Threading.Tasks.Task`1.GetResultCore(Boolean waitCompletionNotification)     
at My.Web.Infrastructure.Filters.ValidateReCaptchaAttribute.OnActionExecuting(ActionExecutingContext filterContext) in My.Web\Infrastructure\Filters\ValidateReCaptchaAttribute.cs:line 49  ---> 
(Inner Exception #0) System.Net.Http.HttpRequestException: An error occurred while sending the request. ---> 
System.Net.WebException: The underlying connection was closed: An unexpected error occurred on a receive. ---> 
System.IO.IOException: Unable to read data from the transport connection: An existing connection was forcibly closed by the remote host. ---> 
System.Net.Sockets.SocketException: An existing connection was forcibly closed by the remote host     
at System.Net.Sockets.NetworkStream.EndRead(IAsyncResult asyncResult)     
--- End of inner exception stack trace ---

我使用属性来验证验证码如下（我删除了一些不重要的细节）：

[AttributeUsage(AttributeTargets.Class | AttributeTargets.Method, AllowMultiple = false, Inherited = true)]
public class ValidateReCaptchaAttribute : ActionFilterAttribute
{
    public override void OnActionExecuting(ActionExecutingContext filterContext)
    {
        var formValues = new[]
        {
            new KeyValuePair<string, string>("privatekey", ConfigurationProvider.ReCaptchaPrivateKey), 
            new KeyValuePair<string, string>("remoteip", remoteIp.ToString()),
            new KeyValuePair<string, string>("challenge", challengeField), 
            new KeyValuePair<string, string>("response", responseField)
        };

        try
        {
            using (var client = HttpClientFactory.Create())
            using (var data = new FormUrlEncodedContent(formValues))
            using (var response = client.PostAsync("http://www.google.com/recaptcha/api/verify", data).Result)
            {
                var responseString = response.Content.ReadAsStringAsync().Result;
                if (responseString.StartsWith("true") == false)
                {
                    modelState.AddModelError(string.Empty, DisplayName.Validation_CaptchaMissing);
                }
            }
        }
        catch (Exception ex)
        {
            log4net.LogManager.GetLogger("WebLogger").Error(string.Format("ValidateReCaptcha failed on {0}/{1}. {2}", controller, action, formValuesRaw), ex);
            modelState.AddModelError(string.Empty, DisplayName.Validation_CaptchaMissing);
        }
    }
}

它在var response = client.PostAsync() 行失败。不总是。我无法在本地复制它。但是对于网站的每个用户来说，它几乎都失败了——有时一次，有时两次，有时更多。最终他们能够注册 - 正如我所说，我看到每小时有 100 多个注册 - 但这会导致该小时的日志表中出现 300-400 个错误。我尝试注册自己 - 虽然我 100% 确定我输入了正确的验证码，但我收到了验证错误。

有什么想法吗？我的验证属性看起来还好吗？还有什么其他原因？

Answer 1

啊！..通过删除修复它

using (var client = HttpClientFactory.Create())

一行并将HttpClient 创建为单例：

public class ValidateReCaptchaAttribute : ActionFilterAttribute
{
    private static readonly HttpClient HttpClient = new HttpClient();
    // rest of the code goes here...

如this SO answer建议的那样