[BitBucket user: Alain Mazy]
[BitBucket date: 2017-05-19.15:54:47]

To evaluate:  The Orthanc service launches Orthanc as a separate process.  It's very likely that this process is killed by the shutdown since Windows does not realize that it's related to a service.

=> we should check if there is a flag that could prevent windows from killing this process.

[BitBucket user: Alain Mazy]
[BitBucket date: 2017-05-20.10:06:25]

An executable can delay Windows shutdown by performing its cleanup while handling the WM_QUERYENDSESSION windows message (https://msdn.microsoft.com/en-us/library/windows/desktop/aa376890(v=vs.85).aspx).  In our case, Orthanc.exe would have to handle this message correctly.

2 solutions to solve this issue:
- Orthanc.exe handles the WM_QUERYENDSESSION message -> we must implement windows message handling in Orthanc.exe
- Orthanc is included as a DLL inside the Orthanc Service and it will be shutdown correctly.

First solution is cleaner since that would also make sure shutdowns are handled correctly for Orthanc processes that are not started by a service.

[BitBucket user: Sébastien Jodogne]
[BitBucket date: 2017-05-20.10:11:08]

Handling WM_QUERYENDSESSION is clearly the way to go.

The following changes have been brought in CL 8ab6399, 5c1695c, 2403546 and be26d8a of the orthanc-builder repository:

- When the service process launches the Orthanc The CREATE_NEW_PROCESS_GROUP is not used anymore. This should prevent a Windows shutdown process to kill Orthanc (only top-level processes are killed)

- SIGINT is only sent to the child process when stopping the service, not when shutting down Windows, since the OS, in the latter case, sends a SIGINT automatically. This prevents the second extraneous signal from being sent.

- The service process itself does not allocate a permanent console. This is cleaner since services should not be attached a console. A console is only temporarily attached when required (i.e. to send the SIGINT signal to Orthanc.exe)

- Instead of an idle waiting period while the service is stopping, the service now properly reports the pending stop operation progress to the Service Control Manager, requesting extra shutdown time until properly stopped.

- The installer process, at uninstall time, now propertly waits for the Orthanc service to stop. This prevents stray files from being left in the install folders (although some files, such as the potentially user-customized configuration files amd the logs are not removed by the installer...)

These fixes greatly improve the situation. Currently, the OS still forcefully kills Orthanc after a few seconds when shutting down an HyperV guest VM running Windows 10 1909). In most scenarios, there should be enough time for Orthanc to properly stop.

This is being investigated.

After some tests where physical installations of Windows 10 behave in the same way (i.e. forcefully killing Orthanc after 5 seconds) and more research, the conclusion is the following :

"Windows normally waits 5 seconds for background services to clean up and close when you tell your computer to shut down."

This delay can be customized through the WaitToKillServiceTimeout registry value.

"Some applications may change this value when you install them, giving their background services extra time to clean up."

(Note: Orthanc does NOT modify this value, neither at installation time or at runtime!)

If you notice that Orthanc (or any service, for that matter) is forcefully killed before being properly shut down (you can check this by performing a shutdown and checking whether the last log line "Orthanc is stopped" can be found in the log after restart), you can change this delay by modifying the 

WaitToKillServiceTimeout value in the HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control registry key.

The values are expressed in milliseconds.

"Double-click the WaitToKillServiceTimeout value and enter a number of milliseconds. The default is 5000 milliseconds, or 5 seconds. To set it to 20 seconds, you’d enter “20000”."


Info has been taken here: https://www.howtogeek.com/282062/control-how-long-windows-waits-before-killing-apps-at-shutdown/