bug#36731: shepherd lost track of nginx

[Robert Vollmert]

Not sure who’s at fault here, but without doing anything weird,
I ended up with a system where shepherd thought that nginx was
stopped, while there was still an nginx process around. I
certainly didn’t start it by hand.

The result was this:

$ sudo herd restart nginx
Service nginx is not running.
herd: exception caught while executing 'start' on service 'nginx':
Throw to key `srfi-34' with args `("#<condition &invoke-error [program: 
\"/gnu/store/mlg0xfbiq03s812rm3v7mrlhyngas4xp-nginx-1.17.1/sbin/nginx\" 
arguments: (\"-c\" \"/gnu/store/r6gl9n7pwf4npiri05qxr40vdihdm2yy-nginx.conf\" 
\"-p\" \"/var/run/nginx\") exit-status: 1 term-signal: #f stop-signal: #f] 
147e000>")’.

That error message could also be clearer about what’s going on. At any
rate, after I killed the nginx process, “herd start nginx” worked fine.

I should add that nginx was still doing its job fine before I killed it.