On 17 May 2018 at 11:58, Mantas Mikulėnas <graw...@gmail.com> wrote:
> this would be anyways broken because systemd reads the PIDFile once at
> start to dtermine MAINPID and if MAINPID goes away the service fails
This is not true as with PIDFile systemd does pick up the new process
as a new main without restarting the unit. This is an example from my
development VM:
systemctl status nginx
...
Active: active (running) since Thu 2018-05-17 11:02:57 UTC; 3min 18s ago
Docs: man:nginx(8)
Process: 2407 ExecStart=/usr/sbin/nginx ...
Main PID: 2408 (nginx)
CGroup: /system.slice/nginx.service
├─2408 nginx: master process ...
├─2409 nginx: worker process
└─2410 nginx: worker process
Initiate a graceful restart of nginx:
kill -s USR2 2408
systemctl status nginx
...
Active: active (running) since Thu 2018-05-17 11:02:57 UTC; 5min ago
Docs: man:nginx(8)
Process: 2407 ExecStart=/usr/sbin/nginx ...
Main PID: 2408 (nginx)
CGroup: /system.slice/nginx.service
├─2408 nginx: master process /usr/sbin/nginx ...
├─2409 nginx: worker process
├─2410 nginx: worker process
├─2418 nginx: master process /usr/sbin/nginx ...
├─2419 nginx: worker process
└─2420 nginx: worker process
Notice that there are 2 master processes, the old one with pid 2408
and the one 2418. Initiate the shutdown of the initial master:
kill -s QUIT 2408
systemctl status nginx
Active: active (running) since Thu 2018-05-17 11:02:57 UTC; 7min ago
Docs: man:nginx(8)
Process: 2407 ExecStart=/usr/sbin/nginx -c
/vol/opt/act/webapp/nginx/nginx.conf -g daemon on; master_process on;
worker_processes auto; pid /run/nginx/nginx.pid; error_log sys
Main PID: 2418 (nginx)
CGroup: /system.slice/nginx.service
├─2418 nginx: master process /usr/sbin/nginx -c
/vol/opt/act/webapp/nginx/nginx.conf -g daemon on; master_process on;
worker_processes auto; pid /run/nginx/nginx.pid;
├─2419 nginx: worker process
└─2420 nginx: worker process
Here systemd correctly recognized 2418 as the new master without
restarting the unit as seen by active time.
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