CODEWITHSUNDEEP
winapi
Scott Langham
Scott Langham

Reputation: 60331

SetThreadpoolTimer, what does it do with an absolute time in the past?

SetThreadpoolTimer is used by my app to periodically ping a server to report my app is alive. My app records the time whenever it sends a ping and persists it to a file.

If my app is restarted it loads the last ping time. What happens if the app calls SetThreadpoolTimer with lastPingTime + period.

Potentially, this time is in the past!

Will SetThreadpoolTimer catch up and fire immediately for the missed event?

If I also specify a period to SetThreadpoolTimer, could the timer immediately fire multiple times to catch up on all the missed events?

The documentation does not explain what happens when using absolute times that are in the past.

Upvotes: 0

Views: 528

Answers (1)

Drake Wu
Drake Wu

Reputation: 7170

There is MSDN sample for Thread Pool Function, and modify it like:

SYSTEMTIME sys = { 0 };
sys.wYear = 2020;
sys.wMonth = 7;
sys.wDay = 6;
sys.wHour = 8;
sys.wMinute = 0; //Suppose the current minute is 20, 0: the past time, 30: the future time.
sys.wSecond = 0;
sys.wMilliseconds = 0;
sys.wDayOfWeek = 1;

SystemTimeToFileTime(&sys,&ft);

SetThreadpoolTimer(timer,
    &ft,
    2000,
    0);

//
// Delay for the timer to be fired
//
Sleep(60000);

The missed event on 8:00 am has been fired immediately, but it only trigger once, then trigger every 2 seconds after it.

So, the short answer is:

Will SetThreadpoolTimer catch up and fire immediately for the missed event?

Yes.

If I also specify a period to SetThreadpoolTimer, could the timer immediately fire multiple times to catch up on all the missed events?

No, it only fire once and then follow the msPeriod to fire the event.

Upvotes: 1

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