Zombie processes inside scheduler container for runInBackground() tasks

[varemel]

Initially I run scheduler inside app container and there was no problem with zombie processes. After I move scheduler to separate container, problem appered.

As I understand this process in simple words: Laravel schedule:run spawn child process for each runInBackground() task and quits. Tasks become zombie (orphan processes = with no parent process) after completion, because supercronic (main init process in container) seems to doesn't know how to 'reap' orphan child processes or doesn't have to.

More on PID 1 zombie reaping problem - https://blog.phusion.nl/2015/01/20/docker-and-the-pid-1-zombie-reaping-problem/

My suggestion is to run scheduler container inside supervisord

start-container

...
elif [ ${container_mode} = "scheduler" ]; then
    initialStuff
    php artisan schedule:clear-cache
    # exec supercronic -overlapping /etc/supercronic/laravel
    exec /usr/bin/supervisord -c /etc/supervisor/conf.d/supervisord.scheduler.conf
...

supervisord.scheduler.conf

[supervisord]
nodaemon=true
user=%(ENV_NON_ROOT_USER)s
logfile=/var/log/supervisor/supervisord.log
# use /var/log, because user has no write permissions to write to /var/run (symlink to /run)
pidfile=/var/log/supervisord.pid

[program:scheduler]
process_name=%(program_name)s_%(process_num)02d
command=supercronic -overlapping /etc/supercronic/laravel
user=%(ENV_NON_ROOT_USER)s
autostart=%(ENV_APP_WITH_SCHEDULER)s
autorestart=true
stdout_logfile=/var/www/html/scheduler.log

I checked this config, and it seems that problem is gone.

[smortexa]

Thanks for your feedbacks! I think that's a good idea.