C# SSL连接无法建立，见内部异常

Question

我试图从支持 TLS 1.3 的站点下载文件。 我在下面收到错误。

System.Net.Http.HttpRequestException: 'The SSL connection could not be established, see inner exception.' AuthenticationException: Authentication failed because the remote party sent a TLS alert: 'DecryptError'.

我还尝试添加： ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls13 | SecurityProtocolType.Tls12; ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls13 | SecurityProtocolType.Tls12;

我也尝试了其他协议，但正如我上面所说，网站支持 tls 1.3。 顺便说一下，当我删除并行 foreach 并运行时它运行良好。 但是，我想批量下载。

我使用 Parallel.ForEach 可能与此有关吗？

            foreach (var directory in directories) 
            {
                if (directory.Contains($"C:\\Websites\\{domain}\\Uploads") || directory.Contains($"C:\\Websites\\{domain}\\CustomCss"))
                {
                    if (directory != null)
                    {
                        var directoryName = directory.Replace($"C:\\Websites\\{domain}\\", "/"); //String.Empty
                        if (directoryName.Contains("\\"))
                        {
                            directoryName = directoryName.Replace("\\", "/");
                        }
                        var createDirectory = await directoryClient.CreateDirectory(new CreateDirectoryRequest { FolderName = directoryName });

                        Parallel.ForEach(Directory.GetFiles(directory), new ParallelOptions { MaxDegreeOfParallelism = 15 }, async (item) =>
                        {
                            if (item != null)
                            {
                                var ms = new MemoryStream();
                                using (FileStream file = new FileStream(item, FileMode.Open, FileAccess.ReadWrite))
                                {
                                    using (ms = new MemoryStream())
                                    {
                                        file.CopyTo(ms);
                                        ms.ToArray();
                                    }
                                }

                                string filename = "";
                                Uri uri = new Uri(item);
                                if (uri.IsFile)
                                {
                                    filename = System.IO.Path.GetFileName(uri.LocalPath);
                                }
                                UploadFileResponse uploadResponse = new UploadFileResponse();

                                if (isImage(MimeMapping.MimeUtility.GetMimeMapping(item)))
                                {
                                    byte[] imageContent = await DownloadAndCompareImages(domain, directoryName + "/" + filename, "90");
                                    uploadResponse = await client.UploadFileAsync(new UploadFileRequest
                                    { FileContent = imageContent, FileName = "/" + directoryName + "/" + filename, ContentType = MimeMapping.MimeUtility.GetMimeMapping(ms.ToString()) });
                                }
                                else
                                {
                                    uploadResponse = await client.UploadFileAsync(new UploadFileRequest
                                    { FileContent = ms.ToArray(), FileName = "/" + directoryName + "/" + filename, ContentType = MimeMapping.MimeUtility.GetMimeMapping(ms.ToString()) });
                                }

                                if (!uploadResponse.IsError)
                                {
                                    finishedProcess++;
                                    fileCounter++;
                                    siteProcess.FinishedProcess = bucketName + " => Site is moving to MinIO...";
                                    siteProcess.FinishedCount = finishedProcess + "/" + totalFileFolder.ToString();
                                    siteProcess.MadePercentage = Convert.ToInt32((100 * (finishedProcess) / totalFileFolder));
                                }
                                else
                                {
                                    isError = true;
                                }

                                if (finishedProcess > totalFileFolder)
                                {
                                    finishedProcess = dataGridSites.SelectedItems.Count;
                                }
                            }
                        });
                    }
                }
            }
            return isError;
        }

其他function为：

        private async Task<byte[]> DownloadAndCompareImages(string domain, string imgFilePath, string imgQuality)
        {
            using var httpClient = new HttpClient();
            httpClient.DefaultRequestHeaders.Add("user-agent", "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/100.0.4896.127 Safari/537.36");

            Uri uriNormalPattern = new Uri($"https://{domain}/{imgFilePath}");

            var uriWithoutQuery = uriNormalPattern.GetLeftPart(UriPartial.Path); //
            var fname = System.IO.Path.GetFileName(uriWithoutQuery);

            var imageBytesNormal = await httpClient.GetByteArrayAsync(uriNormalPattern); //
            int imageWidth = GetImgWidth(imageBytesNormal);

            var imageBytesCloudFlare = await GetCloudFlareImg(domain, imageWidth, imgQuality, imgFilePath);

            if (imageBytesNormal.Length > imageBytesCloudFlare.Length)
            {
                return imageBytesCloudFlare;
            }
            else
            {
                return imageBytesNormal;
            }
        }

Answer 1

使用Parallel.ForEach时，会在短时间内将大量请求发送到服务器。 这可能会使服务器不堪重负，而且HttpClient在并行访问同一域时也会受到限制。

为了缓解这种情况，以下步骤可能会有所帮助：

• 您不应直接创建HttpClient实例，而应使用IHttpClientFactory来创建实例。 有关详细信息，请参阅此链接。 这避免了“通过池化 HttpMessageHandler 实例的资源耗尽问题”。
• 正如您已经做过的那样，限制并行度有助于避免服务器不堪重负。 最佳值只能猜测（可能小于 15），但应该是可配置的，以便在无需重新编译的情况下更改生产中的值。
• 鉴于图像不会改变并且您需要重复请求相同的图像，您可以将图像缓存在您的服务中。 这将减少提供图像的服务器上的负载并加快处理速度。