How to interrupt child process running on a remote machine started by Popen on a host

Question

For my setup, I have a host machine and a remote machine, such that I have direct ssh access from the host machine to the remote one.

I'm using the host machine to start up (and possibly stop) a server, which is a long running process. For that I use subprocess.Popen in which the command looks something like this:

ssh remote_machine "cd dir ; python3 long_running_process.py"

via

p = subprocess.Popen(['ssh', 'remote_machine', 'cd dir ; python3 long_running_process.py'])

From what I gathered, although for the Popen call, we have shell=False, this would anyway enable the ssh process to run the cd and python processes under a shell like bash.

The problem arises when I want to stop this process, or more crucially when an Exception is raised in the long running process, to clean up and stop all processes on the host and most importantly on the remote machine.

Therefore, terminating the Popen process on the host machine does not suffice (actually, I send a SIGINT so that I could catch it on the remote side, but doesn't work), as the long running process still runs on the remote machine.

So if it actually occured that an exception was raised by THE CHILDREN PROCESSES of the long running process, then the long running process itself is not stopped.

Should I have to ssh again to stop the processes? (though I don't know the children's PIDs upfront)