Note that the "retry loop for deleting the executable" technique has zero wait time if the delete succeeds.
A year or so ago I submitted a bug report because I had a program that ran hundreds of external processes (one at a time), and my Go program was way slower that a Python program that did the same thing. Turns out that it was because of the unconditional 5ms delay that was built into the Windows incantation of os (Go\src\os\exec_windows.go). This is an excerpt from that file: // NOTE(brainman): It seems that sometimes process is not dead // when WaitForSingleObject returns. But we do not know any // other way to wait for it. Sleeping for a while seems to do // the trick sometimes. // See https://golang.org/issue/25965 for details. defer time.Sleep(5 * time.Millisecond) defer p.Release() Seems like a great idea to have zero delay except in those few times that it is necessary. On Sat, Aug 15, 2020 at 9:31 AM Bob Alexander <bobja...@gmail.com> wrote: > Here's what I think is really going on: > > At the end of a process's execution, 2 things happen: > - The process's code finishes its execution -- wait returns. > - The OS closes the executable file. > > The second item always "comes after" the first. On Windows the delay might > be a few milliseconds, which can cause a problem, since an attempt to > delete the executable right after wait returns can fail because the > executable is still open. On Unix, this is not a problem because it's OK to > "remove" an open file -- the file doesn't actually get deleted until all > openers have closed the file. > > At one time, Go's os/exec for Windows had a built-in unconditional 5ms > delay to prevent this from happening. Not sure if it still does that. > > It seems that, on Windows, if a program wants to delete the executable > right after its process has finished, if should put the delete in a little > retry loop: > loop a few times (10?) > try do delete the executable > if the delete succeeds > exit this loop > wait a short time (1 ms ?) > announce an error -- executable could not be deleted in reasonable time > after process completion > > This retry loop would be the responsibility of any Windows program that > wants to delete the executable file after its execution finishes. > In reality, this is not done in very many places, done only by some tools > like "go run" (build, run, delete), and the occasional user-written tool. > The vast majority of places where external processes are run leave the > executable file alone after process completion. > > Is it the responsibility of an OS like Windows the guarantee the the > executable is closed when a process wait returns? I would say not, because > that might cause a (small) delay in the vast majority of external process > executions where the executable is not deleted immediately after. > > > On Friday, August 14, 2020 at 8:55:55 AM UTC-7, jake...@gmail.com wrote: >> >> > Turns out it takes some time to release the lock on the folder, so we >> should do some time.Sleep before the os.Remove, so that Windows can release >> the lock. >> >> I do not believe that should be the case under normal Windows operation. >> Using a Sleep in a case like this is always a hack. Sometimes it is the >> only way, but it can fail randomly, especially under stress. There is >> likely something else going on. Could be poorly written antivirus software, >> or a finalizer that has not run in your go app, or something else. If it is >> ok for it to work "most of the time", then maybe your Sleep() solution is >> sufficient. But if you need real reliability, I suggest figuring out what >> is really going on. >> >> On Friday, August 14, 2020 at 10:10:44 AM UTC-4 atakanc...@gmail.com >> wrote: >> >>> Hello guys, I have solved the issue. >>> >>> Turns out it takes some time to release the lock on the folder, so we >>> should do some time.Sleep before the os.Remove, so that Windows can release >>> the lock. >>> >>> Thank you both for replying. >>> >>> 14 Ağustos 2020 Cuma tarihinde saat 16:21:17 UTC+3 itibarıyla >>> jake...@gmail.com şunları yazdı: >>> >>>> This works fine for me on Windows 10. >>>> What is "my.exe" doing? >>>> Do you have third party antivirus software? If so, try turning it off. >>>> They are notorious for causing this kind of problem. >>>> >>>> On Friday, August 14, 2020 at 5:02:36 AM UTC-4 atakanc...@gmail.com >>>> wrote: >>>> >>>>> Hello dear fellow gophers, >>>>> >>>>> I had a relatively simple yet quite inconvenient issue which I felt >>>>> the need to ask here. In my main() function; >>>>> >>>>> os.Remove("my.exe") // err is nil, my.exe is removed >>>>> >>>>> works in Windows without any errors, but when I call exec beforehand, >>>>> I get access is denied error; >>>>> >>>>> buffer, err := exec.Command("my.exe", myArgs...).Output() // err is >>>>> nil here, I get desired output >>>>> os.Remove("my.exe") // remove "C:\\.......\my.exe": Access is denied >>>>> >>>>> I tried using cmd.Process.Kill(), cmd.Process.Wait(), >>>>> cmd.Start()-ioutil.ReadlAll()-cmd.Wait() alternatives as well. I kept >>>>> getting no errors until 'Access is denied'. >>>>> >>>>> I'm using go1.14 linux/amd64 for my compiler and Windows 10 Enterprise >>>>> 10.0.18362. >>>>> >>>>> Thank you. >>>>> >>>> -- > You received this message because you are subscribed to a topic in the > Google Groups "golang-nuts" group. > To unsubscribe from this topic, visit > https://groups.google.com/d/topic/golang-nuts/XglcNW0USuc/unsubscribe. > To unsubscribe from this group and all its topics, send an email to > golang-nuts+unsubscr...@googlegroups.com. > To view this discussion on the web visit > https://groups.google.com/d/msgid/golang-nuts/f0a33b3f-a342-4a9a-9ccc-b0265bd2d60ao%40googlegroups.com > <https://groups.google.com/d/msgid/golang-nuts/f0a33b3f-a342-4a9a-9ccc-b0265bd2d60ao%40googlegroups.com?utm_medium=email&utm_source=footer> > . > -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. 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