Swap the order of terminating workers: from worker first to childs first

[ichuan]

Currently when circus terminating a worker, it sends signal to worker, and then to each child process.

But according to send_signal_child , when sending signals to a child, psutil's Process.children() is used to live query the children of the parent worker process, which is signaled death before. This is the cause that child process don't receive signal.

A workaround is changing the order, and send signal to childs first.

May be a fix for #1044

[coveralls]

Coverage increased (+0.01%) to 62.866% when pulling 3896985 on ichuan:master into 583e2c1 on circus-tent:master.

[k4nar]

Thanks you for your contribution!

Could you try to add a unit test to ensure this behavior? This is such a sensitive part of the code, I would be more confident if this was tested :) .

[bugchecker]

If self.send_signal_process called by self.kill_process, recursive first time will be False. So process.children() return only direct children. If parent process terminated but not terminate all its childs, in the future after graceful_timeout self.send_signal_process will be called once again with recursive=True. But process.children() will not be able to return the children because parent process will not exist and the children will be "orphaned".

I suppose for that case full list of the children should be saved previously, before first calling of the self.send_signal_process in self.kill_process (and used for detect is_alive and sending signals to children). One more thought: when was detected is_alive=False for parent process, do check is_alive for its children and send SIGTERM signals if alive (to not wait graceful_timeout and not terminate its emergency).

Tested with npm start which starts and finishes (after SIGTERM) sh -c "..." but does not finish children started by sh -c "...".

[bugchecker]

#1092 (comment)