| Message ID | 20230413012408.2759-1-maxim.cournoyer@gmail.com |
|---|---|
| State | New |
| Headers | show |
| Series | Add reload action to syslog service. | expand |
Maxim Cournoyer <maxim.cournoyer@gmail.com> skribis: > Having the configuration live at a static location makes it possible to > hot-reload it. > > * gnu/services/base.scm (syslog.conf): New variable. > (syslog-etc, syslog-shepherd-service): New procedures. > (syslog-service-type): Rewrite using the above new variable and procedures, > extending etc-service-type with its configuration file. I’m really not a fan of static configuration file names: you can never be sure what config the service is using—compare this with the unambiguous ‘--config=/gnu/store/…example.conf’. Unfortunately there’s often no other option if we want to support live reconfiguration—there’s only so much a signal can convey. So I guess it’s a “weak accept” from me, because live reload is useful. With the Shepherd in ‘master’, there’s a hook to change a service’s “running value” so it should be possible to stop the previous process, start a new one, and update the service’s running value (which is not equivalent to SIGHUP, but maybe good enough for some cases). A simpler approach might be run the service in a container with /gnu/store/…conf mapped to a fixed location, and somehow update that mapping as we go. Food for thought! Ludo’.
Hello, Ludovic Courtès <ludo@gnu.org> writes: > Maxim Cournoyer <maxim.cournoyer@gmail.com> skribis: > >> Having the configuration live at a static location makes it possible to >> hot-reload it. >> >> * gnu/services/base.scm (syslog.conf): New variable. >> (syslog-etc, syslog-shepherd-service): New procedures. >> (syslog-service-type): Rewrite using the above new variable and procedures, >> extending etc-service-type with its configuration file. > > I’m really not a fan of static configuration file names: you can never > be sure what config the service is using—compare this with the > unambiguous ‘--config=/gnu/store/…example.conf’. Right; although now if you aren't sure what is used you can 'reload' it, eh :-). > Unfortunately there’s often no other option if we want to support live > reconfiguration—there’s only so much a signal can convey. > > So I guess it’s a “weak accept” from me, because live reload is useful. OK! > With the Shepherd in ‘master’, there’s a hook to change a service’s > “running value” so it should be possible to stop the previous process, > start a new one, and update the service’s running value (which is not > equivalent to SIGHUP, but maybe good enough for some cases). Wouldn't that be equivalent to restarting the service? I wasn't aware of the new hook facility, I'll have to read on it, thanks! > A simpler approach might be run the service in a container with > /gnu/store/…conf mapped to a fixed location, and somehow update that > mapping as we go. Food for thought! Interesting idea... although it'd only be compatible with Linux and I dislike writing special cases in services (or anywhere if I can help it).
Hi! Maxim Cournoyer <maxim.cournoyer@gmail.com> skribis: > Ludovic Courtès <ludo@gnu.org> writes: [...] >> I’m really not a fan of static configuration file names: you can never >> be sure what config the service is using—compare this with the >> unambiguous ‘--config=/gnu/store/…example.conf’. > > Right; although now if you aren't sure what is used you can 'reload' it, > eh :-). True. :-) The other issue is that that makes it impossible to run several instances of the service (not a problem for syslogd of course, but could be an issue elsewhere). >> With the Shepherd in ‘master’, there’s a hook to change a service’s >> “running value” so it should be possible to stop the previous process, >> start a new one, and update the service’s running value (which is not >> equivalent to SIGHUP, but maybe good enough for some cases). > > Wouldn't that be equivalent to restarting the service? I wasn't aware > of the new hook facility, I'll have to read on it, thanks! There’s nothing to read :-) and it wasn’t designed with that use case in mind, but we’ll see. >> A simpler approach might be run the service in a container with >> /gnu/store/…conf mapped to a fixed location, and somehow update that >> mapping as we go. Food for thought! > > Interesting idea... although it'd only be compatible with Linux and I > dislike writing special cases in services (or anywhere if I can help > it). Yeah. Ludo’.
diff --git a/gnu/services/base.scm b/gnu/services/base.scm index e5c6bf5335..1ed874aa84 100644 --- a/gnu/services/base.scm +++ b/gnu/services/base.scm @@ -15,7 +15,7 @@ ;;; Copyright © 2020, 2021 Brice Waegeneire <brice@waegenei.re> ;;; Copyright © 2021 qblade <qblade@protonmail.com> ;;; Copyright © 2021 Hui Lu <luhuins@163.com> -;;; Copyright © 2021, 2022 Maxim Cournoyer <maxim.cournoyer@gmail.com> +;;; Copyright © 2021, 2022, 2023 Maxim Cournoyer <maxim.cournoyer@gmail.com> ;;; Copyright © 2021 muradm <mail@muradm.net> ;;; Copyright © 2022 Guillaume Le Vaillant <glv@posteo.net> ;;; Copyright © 2022 Justin Veilleux <terramorpha@cock.li> @@ -1526,30 +1526,43 @@ (define-record-type* <syslog-configuration> (config-file syslog-configuration-config-file (default %default-syslog.conf))) -(define syslog-service-type - (shepherd-service-type - 'syslog - (lambda (config) - (define config-file - (syslog-configuration-config-file config)) +;;; Note: a static file name is used for syslog.conf so that the reload action +;;; work as intended. +(define syslog.conf "/etc/syslog.conf") - (shepherd-service - (documentation "Run the syslog daemon (syslogd).") - (provision '(syslogd)) - (requirement '(user-processes)) - (actions (list (shepherd-configuration-action config-file))) - (start #~(let ((spawn (make-forkexec-constructor - (list #$(syslog-configuration-syslogd config) - "--rcfile" #$config-file) - #:pid-file "/var/run/syslog.pid"))) - (lambda () - ;; Set the umask such that file permissions are #o640. - (let ((mask (umask #o137)) - (pid (spawn))) - (umask mask) - pid)))) - (stop #~(make-kill-destructor)))) - (syslog-configuration) +(define (syslog-etc configuration) + (match-record configuration <syslog-configuration> + (config-file) + (list `(,(basename syslog.conf) ,config-file)))) + +(define (syslog-shepherd-service config) + (define config-file + (syslog-configuration-config-file config)) + + (shepherd-service + (documentation "Run the syslog daemon (syslogd).") + (provision '(syslogd)) + (requirement '(user-processes)) + (actions (list (shepherd-configuration-action syslog.conf))) + (start #~(let ((spawn (make-forkexec-constructor + (list #$(syslog-configuration-syslogd config) + #$(string-append "--rcfile=" syslog.conf)) + #:pid-file "/var/run/syslog.pid"))) + (lambda () + ;; Set the umask such that file permissions are #o640. + (let ((mask (umask #o137)) + (pid (spawn))) + (umask mask) + pid)))) + (stop #~(make-kill-destructor)))) + +(define syslog-service-type + (service-type + (name 'syslog) + (default-value (syslog-configuration)) + (extensions (list (service-extension shepherd-root-service-type + (compose list syslog-shepherd-service)) + (service-extension etc-service-type syslog-etc))) (description "Run the syslog daemon, @command{syslogd}, which is responsible for logging system messages.")))