我正在使用Renci SSH.NET软件包2016版。我正在从外部服务器下载文件。我通常可以每6秒下载一个文件,当你有数千个文件时这是不好的。 我最近尝试将foreach
循环更改为Parallel.ForEach
。这样做可以将下载的文件更改为1.5秒。除非我检查文件时它们都有0 KB,所以它没有下载任何东西。并行循环有什么问题吗?我是C#的新手,并试图改善下载时间
Parallel.ForEach(summary.RemoteFiles, (f, loopstate) =>
{
//Are we still connected? If not, reestablish a connection for up to a max of "MaxReconnectAttempts"
if (!sftp.IsConnected)
{
int maxAttempts = Convert.ToInt32(ConfigurationManager.AppSettings["MaxReconnectAttempts"]);
StatusUpdate(this, new Types.StatusUpdateEventArgs() { message = "SFTP Service has been connected from remote system, attempting to reconnect (" + sftpConnInfo.Host + ":" + sftpConnInfo.Port.ToString() + remotePath + " - Attempt 1 of " + maxAttempts.ToString() + ")", Location = locationName });
for (int attempts = 1; attempts <= maxAttempts; attempts++)
{
sftp.Connect();
if (sftp.IsConnected)
{
StatusUpdate(this, new Types.StatusUpdateEventArgs() { message = "SFTP Service - Connection reestablished (" + remotePath + ")", Location = locationName });
break;
}
else
{
if ((attempts + 1) <= maxAttempts)
{
StatusUpdate(this, new Types.StatusUpdateEventArgs() { message = "SFTP Service still disconnected from remote system, preparing another reconnect attempt (" + sftpConnInfo.Host + ":" + sftpConnInfo.Port.ToString() + remotePath + " - Attempt " + (attempts + 1).ToString() + " of " + maxAttempts.ToString() + ")", Location = locationName });
System.Threading.Thread.Sleep(2000);
}
else
{
//Max reconnect attempts reached - end the session and ensure the appropriate "failure" workflow is triggered
connectionLost = true;
}
}
}
}
if (connectionLost)
loopstate.Break();
// break;
totalFileCount++;
try
{
if (!System.IO.File.Exists(localSaveLocation + f.FileName))
{
System.Diagnostics.Debug.WriteLine("\tDownloading file " + totalFileCount.ToString() + "(" + f.FileName + ")");
System.IO.Stream localFile = System.IO.File.OpenWrite(localSaveLocation + f.FileName);
//Log remote file name, local file name, date/time start
start = DateTime.Now;
sftp.DownloadFile(f.FullName, localFile);
end = DateTime.Now;
//Log remote file name, local file name, date/time complete (increment the "successful" downloads by 1)
timeElapsed = end.Subtract(start);
runningSeconds += timeElapsed.TotalSeconds;
runningAvg = runningSeconds / Convert.ToDouble(totalFileCount);
estimatedSecondsRemaining = (summary.RemoteFiles.Count - totalFileCount) * runningAvg;
elapsedTimeString = timeElapsed.TotalSeconds.ToString("#.####") + " seconds";
System.Diagnostics.Debug.WriteLine("\tCompleted downloading file in " + elapsedTimeString + " " + "(" + f.FileName + ")");
downloadedFileCount++;
ProcessFileComplete(this, new Types.ProcessFileCompleteEventArgs() { downloadSuccessful = true, elapsedTime = timeElapsed.TotalSeconds, fileName = f.FileName, fullLocalPath = localSaveLocation + f.FileName, Location = locationName, FilesDownloaded = totalFileCount, FilesRemaining = (summary.RemoteFiles.Count - totalFileCount), AvgSecondsPerDownload = runningAvg, TotalSecondsElapsed = runningSeconds, EstimatedTimeRemaining = TimeSpan.FromSeconds(estimatedSecondsRemaining) });
f.FileDownloaded = true;
if (deleteAfterDownload)
sftp.DeleteFile(f.FullName);
}
else
{
System.Diagnostics.Debug.WriteLine("\tFile " + totalFileCount.ToString() + "(" + f.FileName + ") already exists locally");
downloadedFileCount++;
ProcessFileComplete(this, new Types.ProcessFileCompleteEventArgs() { downloadSuccessful = true, elapsedTime = 0, fileName = f.FileName + " (File already exists locally)", fullLocalPath = localSaveLocation + f.FileName, Location = locationName, FilesDownloaded = totalFileCount, FilesRemaining = (summary.RemoteFiles.Count - totalFileCount), AvgSecondsPerDownload = runningAvg, TotalSecondsElapsed = runningSeconds, EstimatedTimeRemaining = TimeSpan.FromSeconds(estimatedSecondsRemaining) });
f.FileDownloaded = true;
if (deleteAfterDownload)
sftp.DeleteFile(f.FullName);
}
}
catch (System.Exception ex)
{
// We log stuff here
}
});
答案 0 :(得分:0)
我不知道你为什么得到空文件。虽然我怀疑你没有关闭localFile
流。
尽管如果您的代码有效,但如果您使用相同的连接进行下载,则几乎不会获得任何性能优势,因为SFTP传输往往受到网络延迟或CPU的限制。您必须使用多个连接来克服这个问题。
查看我的answer on Server Fault about factors that affect SFTP transfer speed。
实现一些连接池,每次都选择一个免费连接。
简单示例:
var clients = new ConcurrentBag<SftpClient>();
Parallel.ForEach(files, (f, loopstate) => {
if (!clients.TryTake(out var client))
{
client = new SftpClient(hostName, userName, password);
client.Connect();
}
string localPath = Path.Combine(destPath, f.Name);
Console.WriteLine(
"Thread {0}, Connection {1}, File {2} => {3}",
Thread.CurrentThread.ManagedThreadId, client.GetHashCode(), f.FullName, localPath);
using (var stream = File.Create(localPath))
{
client.DownloadFile(f.FullName, stream);
}
clients.Add(client);
});
Console.WriteLine("Closing {0} connections", clients.Count);
foreach (var client in clients)
{
client.Dispose();
}
你应该以某种方式限制连接数。