Stopping subprocess ran by exec.command in golang - linux

Question

This might seems like a similar question roaming around on the internet but it not as I didn't find any similar, so asking here.
The thing is, I have a go program named abc.go which contains two functions which are to run and stop someScript.sh script. Run() and stop() are being called at API hit. I am running this abc.go file using command sudo go run abc.go someFolder/someScript.sh, while passing someScript.sh path as argument. Instop(), I am saving the process-groupID and then killing the whole process-group.
But when I call run and then stop functions, it gives me this output
pid=5844 duration=13.667µs err=exec: already started
and doesn't actually stop the running docker container (I am checking using docker container ls -a ).
The someScript.sh file is:
#!/bin/bash
docker container run --rm --name someContainerName nginx
The abc.go file is:
func Run(){
someVar= true
execCMD = exec.Command("/bin/sh", "-c", commandFromTerminal)
output, err = execCMD.CombinedOutput()
fmt.Println("Output()=", bp.Output())
someVar= false
}
func Stop(){
execCMD.SysProcAttr = &syscall.SysProcAttr{Setpgid: true}
start := time.Now()
syscall.Kill(-execCMD.Process.Pid, syscall.SIGKILL)
err := execCMD.Run()
fmt.Printf("pid=%d duration=%s err=%s\n", execCMD.Process.Pid, time.Since(start),
err)
}
As per my understanding, it seems like docker command which is written in someScript.sh, didn't run the docker container as a subchild/grandchild of /bin/bash but rather ran it as a separate process which the code in my stop() is unable to actaully stop it
Below is the flow diagram which is according to my understanding where i think on calling abc.go, it internally calling /bin/bash, then running sudo as its child, further sudo has a subchildsomeScript.sh. And finally the docker, which is not running as any child/subchild of the above hierarchy, but as a different process.
My question finally is, how to stop this docker container on calling stop(). Or how to make this docker container run as a subchild of the hierarchy so that I can kill it using process-groupID method which I have used above.
PS: I have also tried
err := execCMD.Process.Kill()
if err != nil {
panic(err.Error())
}
execCMD.Process.Release()
but it too didn't help.

Answer 1

docker is just a client for the docker daemon. docker run simply sends a few HTTP requests to the daemon, and the daemon sets up the container and executes it.
So docker run is a grandchild of your Go program, but the nginx processes are descendants of the Docker daemon, and entirely unrelated to your Go program. Mind you, the docker daemon can even be on a different machine, in principle at least.
That being said,
Assigning SysProcAttr after a process has been started has no effect.
You're calling Run in Stop (very suspicious) and you cannot Run a process that has already been started, even after it terminated.
Sending SIGKILL gives docker run no chance to terminate the container. After fixing the other errors, it's possible that the docker daemon takes care of the cleanup due to the --rm flag (I forget how this works, exactly). If not, send SIGTERM instead.