Question

I have a socket server that used threading to open a thread for each client that connects.
I also have two other threads that run constantly that are doing maintenance operations.

Basically there is the main thread plus two children running constantly, plus one child for each client that connects.

I want to be able to terminate or restart safely.

I would like to be able to trigger a termination function somehow that would instruct all child processes to terminate safely and then the parent could exit.

Any ideas?

Please do not suggest to connect as a client and send a command that would trigger that.
Already thought of it.

I am looking for a way to do this by executing something in the console.

The python socket server runs as a system service and would like to implement the termination in the init script.

Answer 1

The best way to do this is setup a signal handler in your main thread. This can be done using the signal module. See: http://docs.python.org/library/signal.html. A good way would be to trap the CTRL-C signal (SIGINT).

Please note that the signal handler can also be a class method, so you do not have to use a global method (it took me a while to discover that).

 def __init__(self):
     signal.signal(signal.SIGINT, self.just_kill_me)

 def just_kill_me(self, sig, frame):
     self.stopped = True
     for t in self.threads:
         t.join()

It is not possible to send the equivalent of a kill signal to a thread. Instead you should set a flag that will signal the children to stop.

Your child threads should run in a loop, periodically checking if the parent requests them to stop.

while not parent.stopped:
    do_some_maintenance_work