Figure out why Python containers don't respond to SIGTERM

[lance]

When run in a container, the Python applications built with these buildpacks don't respond to SIGTERM. When the same commands are run in a local execution environment, the applications respond correctly.

#60 (comment)

[matejvasek]

Seems that for some reason python is ignoring most of the signals when running with pid 1.

[matejvasek]

Well, at least default handlers are not working when pid == 1.

This could be fixed by installing own handlers:

def receive_signal(signal_number, frame):
    sys.stderr.write('Received: ' + str(signal_number) + "\n")
    sys.exit(1)
    return


signal.signal(signal.SIGTERM, receive_signal)
signal.signal(signal.SIGINT, receive_signal)

[matejvasek]

Note that code above terminates python quite ungracefully by sys.exit(), maybe it could be done better.

[matejvasek]

@lance I looked into it a bit ^^^

[matejvasek]

this probably should be fixed in parliament project

[lance]

@lance I looked into it a bit ^^^

Thank you! This is very helpful.

this probably should be fixed in parliament project

Agree

[lance]

@matejvasek this is some good and relevant reading https://hackernoon.com/my-process-became-pid-1-and-now-signals-behave-strangely-b05c52cc551c

[matejvasek]

@matejvasek this is some good and relevant reading https://hackernoon.com/my-process-became-pid-1-and-now-signals-behave-strangely-b05c52cc551c

That checks out. The other two runtimes: golang and Quarkus are explicitly handling and they work as expected.

[lance]

@matejvasek see #70

this probably should be fixed in parliament project

After reading more about the problem, I don't think the solution belongs with parliament, since that would require that parliament actually implement a lot of stuff that is unrelated to what it does - e.g. reaping zombie and orphaned processes. Other tools like dumb-init are explicitly designed for this.

[matejvasek]

After reading more about the problem, I don't think the solution belongs with parliament, since that would require that parliament actually implement a lot of stuff that is unrelated to what it does - e.g. reaping zombie and orphaned processes.

@lance I think it should be fixed in both:
#68
boson-project/parliament#2

[matejvasek]

implement a lot of stuff that is unrelated to what it does - e.g. reaping zombie and orphaned processes.

why?

[lance]

why?

Well, that's what an init process is supposed to do. But of course, you are right to question this since parliament was previously PID 1. So, fair point. :)