Re: Custom Service Definition for Caddy

[Efraim Flashner <efraim@flashner.co.il>]

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On Tue, Jan 26, 2021 at 11:02:58AM -0600, Cameron wrote:
> Hello again everyone!
> 
> I'm having a great time learning about Guix, but am struggling with defining a custom service for Caddy. The 'caddy' package below works as expected -- installing it puts the "caddy" binary in $PATH and it works fine when I run it from a shell.
> 
> 
> #+begin_src 
<code snipped>
> #+end_src
> 
> What doesn't work as expected is this service definition:
> 
> #+begin_src 
> (define-record-type* <caddy-configuration>
>   caddy-configuration  make-caddy-configuration caddy-configuration?
>   (config-file          caddy-configuration-config-file
>                         (default "/etc/Caddyfile")))
> 
> (define caddy-service-type
>   (shepherd-service-type
>    'caddy
>    (lambda (config)
>      (shepherd-service
>       (documentation "Run the caddy daemon (caddy).")
>       (provision '(caddy))
>       (requirement '(user-processes))
>       (start #~(make-forkexec-constructor
> 			     (list "caddy" "run"
> 				   "-config" "/etc/Caddyfile")
> 				   #:log-file "/var/log/caddy.log"))
>       (stop #~(make-kill-destructor))))))
> #+end_src
> 
> ...which I then add to my services list in config.scm like this:
> 
> #+begin_src 
> 			 (service caddy-service-type
> 				  (caddy-configuration
> 				   (config-file "/etc/Caddyfile")))
> #+end_src
> 
> With this setup, 'herd start caddy' hangs for 30 seconds, during which time the server is active and taking traffic according to the config in /etc/Caddyfile but then something (presumably Shepherd) sends it a SIGTERM and it dutifully shuts down. The 'herd start caddy' then exits with an error:
> 
> #+begin_src 
> root@tindall ~# START=$(date +%s); herd start caddy; END=$(date +%s); echo $(($END - START))
> Service caddy could not be started.
> herd: failed to start service caddy
> 30
> root@tindall ~# tail -n 1 /var/log/caddy.log 
> {"level":"info","ts":1611680035.1811087,"msg":"shutdown done","signal":"SIGTERM"}
> root@tindall ~# 
> #+end_src
> 
> 'caddy run' will keep caddy in the foreground, but I see the same behavior when I use 'caddy start' (which forks another process for the daemon and exits immediately) in the service definition instead.
> 
> I suspect something is wrong with the 'start' procedure I've defined, but I'm struggling to figure out what it is.
> 
> What am I missing?
> 
> -Cameron
> 

Does caddy fork when you run "caddy run?" 'make-fork-constructor' forks
when it runs the code, so if caddy also forks then you have a
double-forked codepath and shepherd thinks the process is gone, so it
goes to kill it. If caddy doesn't have something like --foreground or
--no-daemonize then you might be looking at something like exec-command
from the manual¹.

Alternatively it might work if you can set a PID file.

¹ https://www.gnu.org/software/shepherd/manual/html_node/Service-De_002d-and-Constructors.html#Service-De_002d-and-Constructors

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Efraim Flashner   <efraim@flashner.co.il>   אפרים פלשנר
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