.NET HttpClient在Azure WebApp中响应缓慢或不响应

Question

我们正在Azure应用服务上运行WebJob和Api。一些WebJob执行对第三方服务（如ebay）的REST呼叫。所有这些都很好，直到几天前，服务开始随机抛出这个错误：

{\"ClassName\":\"System.Net.Http.HttpRequestException\",\"Message\":\"An error occurred while sending the request.\",\"Data\":{},\"InnerException\":{\"ClassName\":\"System.Net.WebException\",\"Message\":\"The underlying connection was closed: An unexpected error occurred on a receive.\",\"Data\":{},\"InnerException\":{\"ClassName\":\"System.IO.IOException\",\"Message\":\"Unable to read data from the transport connection: A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond.\",\"Data\":{},\"InnerException\":{\"NativeErrorCode\":10060,\"ClassName\":\"System.Net.Sockets.SocketException\",\"Message\":\"A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond\",\"Data\":{},\"InnerException\":null,\"HelpURL\":null,\"StackTraceString\":\"   at System.Net.Sockets.Socket.EndReceive(IAsyncResult asyncResult)\\r\\n   at System.Net.Sockets.NetworkStream.EndRead(IAsyncResult asyncResult)\",\"RemoteStackTraceString\":null,\"RemoteStackIndex\":0,\"ExceptionMethod\":\"8\\nEndReceive\\nSystem, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089\\nSystem.Net.Sockets.Socket\\nInt32 EndReceive(System.IAsyncResult)\",\"HResult\":-2147467259,\"Source\":\"System\",\"WatsonBuckets\":null},\"HelpURL\":null,\"StackTraceString\":\"   at System.Net.Security._SslStream.EndRead(IAsyncResult asyncResult)\\r\\n   at System.Net.TlsStream.EndRead(IAsyncResult asyncResult)\\r\\n   at System.Net.Connection.ReadCallback(IAsyncResult asyncResult)\",\"RemoteStackTraceString\":null,\"RemoteStackIndex\":0,\"ExceptionMethod\":\"8\\nEndRead\\nSystem, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089\\nSystem.Net.Security._SslStream\\nInt32 EndRead(System.IAsyncResult)\",\"HResult\":-2146232800,\"Source\":\"System\",\"WatsonBuckets\":null}

调用有时工作，但非常慢，有时会返回错误。运行服务的本地实例不会导致失败。只有在正式生产环境中，我们才会遇到这些问题。

我们使用HttpClient的一个单例实例来执行调用。

public sealed class Client : HttpClient
    {
        private static volatile Client _instance = new Client();

        static Client()
        {
        }

        private Client() : base(new NativeMessageHandler())
        {
            // limit the connections in parallel to 100 by default
            ServicePointManager.ServerCertificateValidationCallback = delegate { return true; };
            ServicePointManager.SecurityProtocol = SecurityProtocolType.Ssl3 | SecurityProtocolType.Tls | SecurityProtocolType.Tls11 | SecurityProtocolType.Tls12;

            // if this setting does not work, follow these instructions on app.config
            // ServicePointManager.DefaultConnectionLimit needs to be set before the ServicePoint is created 
            ServicePointManager.DefaultConnectionLimit = 100;
        }

        public static Client Instance => _instance;
    }

我们这样使用客户端调用endpoint：

var client = Client.Instance;
var authenticationHeader = new AuthenticationHeaderValue("Bearer", token.AuthToken);
var url = "https://api.ebay.com/sell/account/v1/fulfillment_policy?marketplace_id=EBAY_DE";
var response = await client.GetMessageAsync(url, m => m.Headers.Authorization = authenticationHeader);

GetMessageAsync方法是一个扩展方法，只执行设置头的操作。

问题开始后不久，微软宣布了这个安全补丁：https://docs.microsoft.com/answers/questions/6842/announcement-samesite-cookie-handling-and-net-fram.html

客户端设置为接受TLS 1.2和1.1。

Answer 1

为了缩小可能的原因，我让易趣和微软支持部门检查了他们的系统。事实证明，这实际上是易趣方面的一个问题。