PHP kill exec() background process after php-fpm restarted

Question

I use nginx and php7.1-fpm. I want to run a background process using PHP and exec().

My short code:

<?php
exec('/usr/local/bin/program > /dev/null 2>&1');

Unfortunately after the systemd restart php7.1-fpm the program is killed.

I have tried to run with a different user than the one running the pool:

<?php
exec('sudo -u another_user /usr/local/bin/program > /dev/null 2>&1');

However, this does not solve the problem - still kills.

I can not use ssh2_connect(). How can I solve this problem?

Try `exec('/usr/bin/nohup /usr/local/bin/program > /dev/null 2>&1');` — Tarun Lalwani, Sep 27 '17 at 20:31
@TarunLalwani It does not work. :( After php-fpm restart the process is killed. — Desavil, Sep 27 '17 at 20:34
I think systemd will reap the child processes on server restart. So not sure if you can really escape that — Tarun Lalwani, Sep 27 '17 at 20:35
Take a look at that: https://stackoverflow.com/questions/16890855/can-we-reload-one-of-the-php-fpm-pool-without-disturbing-others — Mohammad Tbeishat, Sep 27 '17 at 21:35
@MohammadTbeishat I want a permanent solution. Eg after php-fpm an update restart will be necessary. — Desavil, Sep 27 '17 at 21:48
What are you running, and why don't you just run it as a separate service? — Sammitch, Sep 27 '17 at 22:08

score 1 · Accepted Answer · edited May 14 '18 at 14:18

It seems this is due to the php-fpm service being managed by the systemd.

All processes launched from php-fpm belong to its control-group and when you restart the service systemd sends the SIGTERM to all the processes in the control-group even if they are daemonized, detached and/or belong to another session.

You can check your control-groups with this command:

systemd-cgls

What I've done is to change the KillMode of the php-fpm service to process. Just edit it's .service file:

vi /etc/systemd/system/multi-user.target.wants/php7.0-fpm.service

and change or add the line to the [Service] block:

KillMode=process

Then reload the configuration by executing:

systemctl daemon-reload

That worked for me.

References: Can't detach child process when main process is started from systemd

http://man7.org/linux/man-pages/man5/systemd.kill.5.html

What would be wonderful would be a command (similar to setsid) that allowed to launch a process and detach from control-group but I haven't been able to find it.

PHP kill exec() background process after php-fpm restarted

1 Answers1