Fiddler crashes on shut-down when running for a long time

[Jan]

On a certain Windows machine Fiddler is always running in background which seem to trigger problems because when ever I want to exit Fiddler (or Windows is shutting down) I am getting an Exception which blocks the Windows shutdown process:

 

System.ComponentModel.Win32Exception (0x80004005): Der RPC-Server ist nicht verfügbar
   bei Telerik.NetworkConnections.Windows.WinINetPInvokes.ExecuteInternetQueryOrSetOption(String connectionName, INTERNET_PER_CONN_OPTION[] pOptions, Func`3 internetQueryOrSetOption, Action`1 success)
   bei Telerik.NetworkConnections.Windows.WinINetPInvokes.SetProxySettingsForNetworkConnection(WinINetProxySettings proxySettings, String connectionName)
   bei Telerik.NetworkConnections.NetworkConnectionsManager.SetProxySettingsForConnections(ProxySettings settings, IEnumerable`1 fullNames)
   bei ..() in C:\Jenkins\Fiddler_Windows\workspace\FiddlerCore\FiddlerCore.Shared\Common\Core\Connectoids.cs:Zeile 199.
   bei Fiddler.Proxy.Detach(Boolean ??) in C:\Jenkins\Fiddler_Windows\workspace\FiddlerCore\FiddlerCore.Shared\Common\Core\Proxy.cs:Zeile 1356.
   bei Fiddler.frmViewer.actDetachProxy() in C:\Jenkins\Fiddler_Windows\workspace\Fiddler2\Fiddler.Shared\Viewer.cs:Zeile 7177.
   bei Fiddler.frmViewer.??(Object , CancelEventArgs ) in C:\Jenkins\Fiddler_Windows\workspace\Fiddler2\Fiddler.Shared\Viewer.cs:Zeile 10773.
   bei System.Windows.Forms.Form.OnClosing(CancelEventArgs e)
   bei System.Windows.Forms.Form.WmClose(Message& m)
   bei Fiddler.frmViewer.WndProc(Message& m) in C:\Jenkins\Fiddler_Windows\workspace\Fiddler2\Fiddler.Shared\Viewer.cs:Zeile 12465.
   bei System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)

 

Note that this happens on all Windows systems I have tried, when ever Fiddler is running for a long time (e.g. multiple days) it is no longer able to shut down cleanly.

 

As I wrote this is a problem as when this Exception occurs the Windows shutdown process is blocked and e.g. a reboot for installing Windows Updates can not continue until someone manually closes the exception dialog. But the error does not have to do anything with the shutdown process. It also occurs when you just close Fiddler after running for a long time.

[Nick Iliev]

Hello Jan,

 

Thank you for reporting that one - we are currently trying to reproduce the issue so far to no avail. Could you clarify what is the version of Windows on which the case is occurring?

 

As a side note, the team is currently developing the new Fiddler Everywhere electron application. Perhaps you could give it a try and see if it fits your needs. Any feedback is much appreciated!

 

Regards,
Nick Iliev
Progress Telerik

[Jan]

Thank you for your response. This problem is bugging me for quite a while, therefore it was present on Windows 10 version 1909, 20H1 and 20H2 (Windows 10 Enterprise no domain).

What I forgot to mention which may be important is that the system where I see this bug is only used via RDP (single user account that is typically never logged-off, only the RDP connection is closed but the user is still logged on).

 

 

[Nick Iliev]

Hi Jan,

 

Could you shed some light on the specifics of your RDP workflow? Here is what I have been testing on my side when trying to reproduce the issue:

1. Using a remote connection to connect to a Windows 10 PC.
2. Starting the classic Fiddler and enabling the capturing.
3.a Leaving the machine for over 24 hours and then reconnecting. The connection requires the domain user to log in when a new remote connection is initiated. At this point, no issue occurs.
3.b Leaving the machine for over 24 hours and then shutting down the remote Windows 10. Still, no issue occurs during the shutdown process.

Please let me know if you have a different setup or if I am missing something during the test flow.

 

Regards,
Nick Iliev
Progress Telerik

[Jan]

Hi Nick,

 

what you describe is more or less my set-up, except for that the Fiddler is directly started via Autostart and then minimized to Tray and the PC is not member of a domain, hence always the same local account is used.

To my experience just closing Fiddler is sufficient to trigger the error but I am not sure if 24 hours are enough "wait time".   

I should also note that this Fiddler passes a lot of data - every week may be a hundred Gigabyte (mostly in requests that have a response of 100-900MB). But that data is just a by-catch I am not interested in (because of the system wide proxy setting).

Therefore I hide nearly all traffic via  oSession["ui-hide"]="hide"; in OnBeforeRequest

[Nick Iliev]

Hi Jan,

 

Thanks for the clarifications. I will try to mock the whole case this weekend so that Fiddler could run without interfering for over 72 hours, and then I will let you know if we can reproduce the issue. Meanwhile, could you send us the FIddler logs generated when the error occurs. You could check the Logs tab for the classic Fiddler and use the timestamp to narrow the logs. For FIddler Everywhere, you could use the Show Logs option or directly grab the logs manually, as shown here.

 

Regards,
Nick Iliev
Progress Telerik

[Jan]

The the fiddler log persisted somewhere? Because I can only make a screenshot of the log tab when the error dialog shows because no matter what I do Fiddler is closed afterwards and the log is gone. And when I restart Fiddler the log starts fresh.

[Nick Iliev]

Hello Jan,

 

For the classic Fiddler, you could open the Logs tab and do a right-click (opens a context menu) and then Save to File.

 

Regards,
Nick Iliev
Progress Telerik