如何将PreShutdown事件添加到ATL服务？

Question

I've inherited the C++ code for an old ATL based service which contains the basic structures from the old ATL wizards (_tWinMain(), Run(), RunMessageLoop() etc).

In particular, this code already handles "Shutdown" and "Stop" events - and I've been asked to add an additional closedown item into the "PreShutdown" event.

I've added the SERVICE_ACCEPT_PRESHUTDOWN option..

m_status.dwControlsAccepted |= SERVICE_ACCEPT_PRESHUTDOWN

..but I can't see how to catch the resulting event - SERVICE_CONTROL_PRESHUTDOWN - as ATL appears to provide for "OnShutdown" and "OnClose" methods but doesn't contain an entry for "OnPreShutdown" that I can see.

Can anyone point me at something which will allow me to add an OnPreShutdown to my existing code?

Answer 1

Implementing services using ATL is covered at ATL Services . To handle control requests that a default ATL-generated service wouldn't, you need to extend the default-generated Handler implementation.

This is a rough sketch for what you need to do (in addition to registering for the control request, which you already are):

void CMyServiceModule::Handler(DWORD dwOpcode) throw() {
    if (SERVICE_CONTROL_PRESHUTDOWN == dwOpcode) {
        // Perform custom handling
    }
    else {
        // Pass all other control codes to default implementation
        __super::Handler(dwOpcode);
    }
}

As an alternative, you could override the OnUnknownRequest member in your custom implementation. This member is called for all codes that aren't handled by the default implementation:

void CMyServiceModule::OnUnknownRequest(DWORD dwOpcode) {
    if (SERVICE_CONTROL_PRESHUTDOWN == dwOpcode) {
        // Perform custom handling
    }
    else {
        // Possibly handle other control codes
    }
}

Answer 2

The main problem is that ATL uses RegisterServiceCtrlHandler instead of RegisterServiceCtrlHandlerEx ; only the second of these actually registers for the SERVICE_CONTROL_PRESHUTDOWN message. Further, ATL does not contain an inheritable template for OnPreShutdown().

The solution is therefore in four parts:

(1) Update the list of accepted control messages to include the SERVICE_ACCEPTED_PRESHUTDOWN message. You can remove the SERVICE_ACCEPTED_SHUTDOWN as Windows deems the service to be shut down once you have handled the Pre-Shutdown so you will never receive this message. In my case the change was to the list of controls set in the overridden PreMessageLoop() method:

I changed: m_status.dwControlsAccepted = SERVICE_ACCEPT_STOP | SERVICE_ACCEPT_SHUTDOWN; m_status.dwControlsAccepted = SERVICE_ACCEPT_STOP | SERVICE_ACCEPT_SHUTDOWN;

To: m_status.dwControlsAccepted = SERVICE_ACCEPT_STOP | SERVICE_ACCEPT_PRESHUTDOWN; m_status.dwControlsAccepted = SERVICE_ACCEPT_STOP | SERVICE_ACCEPT_PRESHUTDOWN;

However you may not have overridden this method - so you should simply change that list at whatever point you are setting this value. (IInspectable (see other answer) recommends considering the constructor.)

(2) Override ServiceMain() , replacing it entirely by cloning the code and updating it to use RegisterServiceCtrlHandlerEx . The key change is:

Change: m_hServiceStatus = RegisterServiceCtrlHandler(m_szServiceName, _Handler);

To: m_hServiceStatus = RegisterServiceCtrlHandlerEx(m_szServiceName, (LPHANDLER_FUNCTION_EX)_Handler, NULL);

but you will also need to change references to pT and T to be this in order to remove the templating code (you can also remove the line defining pT ); for example:

Change: hr = T::InitializeCom();

To: hr = this->InitializeCom();

Do not include a call to the base class (as this would include a call to RegisterServiceCtrlHandler ).

(3) Override and extend Handler() . This requires the addition of new code such as:

void CServiceModule::Handler(_In_ DWORD dwOpcpde) throw()
{
    switch (dwOpcode)
    {
        case SERVICE_CONTROL_PRESHUTDOWN:
            this->OnPreShutdown();
            break;

        default:
            __super::Handler(dwOpcode);
            break;
    }
}

(Thanks to IInspectable (see other answer) for helping point me in the right direction on this bit.)

(4) You can now implement an OnPreShutdown() method:

void CServiceModule::OnPreShutdown() throw()
{
    // custom handling code
    // ...

    // note: service must shutdown in this handler, so finish
    //       by notifying this to SCM.
    SetServiceStatus(SERVICE_STOPPED);
}

Note that Windows expects the service to be stopped during the pre-shutdown if you use it, and once the above is implemented your service will not receive any SERVICE_CONTROL_SHUTDOWN messages (as it should already be shut down). To allow Windows to carry on shutting other services down you therefore need to add a final SetServiceStatus(SERVICE_STOPPED) call at the end of your OnPreShutdown() method.