Downloading SFTP files through WinSCP on a Windows Service freezes - windows

Question

I'm trying to build a service that downloads some log files using SFTP and imports them to the database.
Because Delphi doesn't come with SFTP components, I have created a BAT file to download the logs using WinSCP
DownloadLogs.bat:
WinSCP.com < DownloadLogs.commands
DownloadLogs.commands:
open sftp://root:password#myserver.com
option confirm off
get -delete /var/lib/3cxpbx/Instance1/Data/Logs/CDRLogs files
exit
This is my service:
procedure TsrvCentralita.ServiceExecute(Sender: TService);
const SecondsBetweenExecutions = 10;
var Counter: integer;
dmLogs: TdmLogs;
begin
Counter := 0;
while not Terminated do begin
Inc(Counter);
if Counter > SecondsBetweenExecutions then begin
Counter := 0;
dmLogs := TdmLogs.Create(Self);
try
if dmLogs.DownloadLogs then dmLogs.ImportLogs;
finally
dmLogs.Free;
end;
end;
Sleep(1000);
ServiceThread.ProcessRequests(False);
end;
end;
And this is how I call the BAT file:
function ExecAppWait(AppName: string; Params: string = ''; Directory: string = ''; Hidden: boolean = False): Boolean;
var ShellExInfo: TShellExecuteInfo;
begin
FillChar(ShellExInfo, SizeOf(ShellExInfo), 0);
with ShellExInfo do begin
cbSize := SizeOf(ShellExInfo);
fMask := see_Mask_NoCloseProcess;
Wnd := Application.Handle;
lpFile := PChar(AppName);
lpDirectory := PChar(Directory);
lpParameters := PChar(Params);
if Hidden then nShow := sw_Hide
else nShow := sw_ShowNormal;
end;
Result := ShellExecuteEx(#ShellExInfo);
if Result then
while WaitForSingleObject(ShellExInfo.HProcess, 100) = WAIT_TIMEOUT do begin
Application.ProcessMessages; // give processor time to other tasks
if Application.Terminated then
Break;
end;
end;
function TdmLogs.DownloadLogs(Hidden: boolean = True): boolean;
var Path: string;
begin
Path := TPath.Combine(TPath.GetDirectoryName(Application.ExeName), 'SFTP');;
ExecAppWait(TPath.Combine(Path, 'LogsCentralita.bat'), '', Hidden);
Result := Length(TDirectory.GetFiles(TPath.Combine(Path, 'Files'), '*.log')) > 0
end;
When I debug the DownloadLogs function on my application, it works fine, but when running as a service it freezes. Do you know what is wrong ?, shouldn't I be able to call CMD.exe from a service ?.
Thank you.
update
Following Martin Prikryl's answer I now execute WinSCP this way:
function TdmCentralita.DownloadLogs(SaveOutput: boolean = False): boolean;
var IniFile: TIniFile;
Path, Params, User, Password, Server, Hostkey, RemotePath: string;
begin
IniFile := TIniFile.Create(TPath.ChangeExtension(GetModuleName(HInstance), '.ini'));
Server := IniFile.ReadString('Centralita', 'Servidor', '');
Hostkey := IniFile.ReadString('Centralita', 'Hostkey', '');
User := IniFile.ReadString('Centralita', 'Usuario', 'root');
Password := DecryptStr(IniFile.ReadString('Centralita', 'Password', ''), 223);
RemotePath := IniFile.ReadString('Centralita', 'PathRemoto', '');
IniFile.Free;
while (RightStr(RemotePath, 1) = '\') or (RightStr(RemotePath, 1) = '/') do RemotePath := Copy(RemotePath, 1, Length(RemotePath) - 1);
RemotePath := RemotePath + '/*.log';
Path := TPath.Combine(TPath.GetDirectoryName(GetModuleName(HInstance)), 'SFTP');
if not TDirectory.Exists(TPath.Combine(Path, 'files')) then TDirectory.CreateDirectory(TPath.Combine(Path, 'files'));
Params := '/ini=null /command "open sftp://' + User + ':' + Password + '#' + Server + ' -hostkey=""' + Hostkey + '""" "option confirm off" "get -delete ' + RemotePath + ' files\*" "exit"';
if SaveOutput then Params := Params + ' /log="' + Path + '\Log.txt" /loglevel=0';
ExecAppWait('WinSCP.com', Params, Path, True);
Result := Length(TDirectory.GetFiles(TPath.Combine(Path, 'Files'), '*.log')) > 0
end;

Answer 1

Your script does not contain SSH host key. And due to the strange way you provide the commands (an input redirection instead of /script or /command switches), WinSCP starts in an interactive mode. So it prompts for hostkey verification, and hangs.
Add -hostkey switch to your open command. See:
Verifying the host key in script
My script works fine when executed manually, but fails or hangs when run by Windows Scheduler, SSIS or other automation service. What am I doing wrong?
And use /script or /command switches to make WinSCP abort on any problem, instead of hanging.
You should also read the batch file output for better error handling in the future.