| Message ID | 7501182c5831ba86d4e600967fb944e9e1124352.1719066498.git.ludo@gnu.org |
|---|---|
| State | New |
| Headers | show |
| Series | [bug#69591] services: shepherd: Support “free-form” services. | expand |
Ludovic Courtès <ludo@gnu.org> skribis: > * gnu/services/shepherd.scm (<shepherd-service>)[free-form]: New field. > [start]: Add default value. > (shepherd-service-file): Rename to… > (shepherd-service-file/regular): … this. > (shepherd-service-file/free-form): New procedure. > (shepherd-service-file): Dispatch to one of the two procedures above. > * doc/guix.texi (Shepherd Services): Document the ‘free-form’ field. > > Change-Id: I206374e950ef6d1e4a996c0f507fb5fcd9cadde3 Oops, wrong issue! (I used ‘mumi send-email’ while this issue was current…)
Hi Ludovic, Ludovic Courtès <ludo@gnu.org> writes: > * gnu/services/shepherd.scm (<shepherd-service>)[free-form]: New field. > [start]: Add default value. > (shepherd-service-file): Rename to… > (shepherd-service-file/regular): … this. > (shepherd-service-file/free-form): New procedure. > (shepherd-service-file): Dispatch to one of the two procedures above. > * doc/guix.texi (Shepherd Services): Document the ‘free-form’ field. > > Change-Id: I206374e950ef6d1e4a996c0f507fb5fcd9cadde3 > --- > doc/guix.texi | 26 +++++++++++++++++++++++++- > gnu/services/shepherd.scm | 25 ++++++++++++++++++++++--- > 2 files changed, 47 insertions(+), 4 deletions(-) > > Hi! > > This patch fixes a limitation that became apparent with Shepherd 0.10, > where users could not instantiate services from the built-in service > collection for which they do not explicitly specify the ‘start’ > and ‘stop’ methods (see REPL service example below). > > Thoughts? > > Ludo’. > > diff --git a/doc/guix.texi b/doc/guix.texi > index 0102fd0fad3..4d9145445cc 100644 > --- a/doc/guix.texi > +++ b/doc/guix.texi > @@ -43909,7 +43909,7 @@ Shepherd Services > When true, this is the delay in seconds before restarting a failed > service. > > -@item @code{start} > +@item @code{start} (default: @code{#~(const #t)}) > @itemx @code{stop} (default: @code{#~(const #f)}) > The @code{start} and @code{stop} fields refer to the Shepherd's > facilities to start and stop processes (@pxref{Service De- and > @@ -43928,6 +43928,30 @@ Shepherd Services > herd @var{action} @var{service} [@var{arguments}@dots{}] > @end example > > +@item @code{free-form} (default: @code{#f}) > +When set, this field replaces the @code{start}, @code{stop}, and > +@code{actions} fields. It is meant to be used when the service > +definition comes from some other source, typically the service > +collection provided by the Shepherd proper (@pxref{Service Collection,,, > +shepherd, The GNU Shepherd Manual}). > + > +@cindex REPL service, for shepherd > +For example, the snippet below defines a service for the Shepherd's > +built-in @acronym{REPL, read-eval-print loop} service (@pxref{REPL > +Service,,, shepherd, The GNU Shepherd Manual}): > + > +@lisp > +(shepherd-service > + (provision '(repl)) > + (modules '((shepherd service repl))) > + (free-form #~(repl-service))) > +@end lisp > + > +In this case, the service object is returned by the @code{repl-service} > +procedure of the Shepherd, so all the @code{free-form} G-expression does > +is call that procedure. Note that the @code{provision} field must be > +consistent with the actual service provision. Hm, if free-form is expected to be a built-in procedure provided by Shepherd, should we call it 'built-in' instead of 'free-form' ? Or could it have a more general use that I'm not seeing. It seems the contract is that it could be any code used 'provision' a shepherd service object, overriding e.g. the start and stop slots. I guess that's more flexibility, and that its 'free-form' name is OK if that's so. The rest LGTM.
Hi Maxim, (Cc’ing 71739, which is actually the right one. :-)) Maxim Cournoyer <maxim.cournoyer@gmail.com> skribis: > Ludovic Courtès <ludo@gnu.org> writes: [...] >> +@item @code{free-form} (default: @code{#f}) >> +When set, this field replaces the @code{start}, @code{stop}, and >> +@code{actions} fields. It is meant to be used when the service >> +definition comes from some other source, typically the service >> +collection provided by the Shepherd proper (@pxref{Service Collection,,, >> +shepherd, The GNU Shepherd Manual}). >> + >> +@cindex REPL service, for shepherd >> +For example, the snippet below defines a service for the Shepherd's >> +built-in @acronym{REPL, read-eval-print loop} service (@pxref{REPL >> +Service,,, shepherd, The GNU Shepherd Manual}): >> + >> +@lisp >> +(shepherd-service >> + (provision '(repl)) >> + (modules '((shepherd service repl))) >> + (free-form #~(repl-service))) >> +@end lisp [...] > Hm, if free-form is expected to be a built-in procedure provided by > Shepherd, should we call it 'built-in' instead of 'free-form' ? I view it as something more generic: it’s typically, but not just, for when the service comes from a procedure defined in the Shepherd itself. Other use case is when as a service author you need more freedom that what you get with the ‘start’ and ‘stop’ fields, like: (shepherd-service ;; … (free-from #~(let ((whatever (spawn-fiber …))) (service '(foo) #:start …)))) It’s probably going to be a relatively marginal use case, but it’s good to have that extra level of flexibility. WDYT? Thanks! Ludo’.
Hi Ludovic, Ludovic Courtès <ludo@gnu.org> writes: [...] >> Hm, if free-form is expected to be a built-in procedure provided by >> Shepherd, should we call it 'built-in' instead of 'free-form' ? > > I view it as something more generic: it’s typically, but not just, for > when the service comes from a procedure defined in the Shepherd itself. > > Other use case is when as a service author you need more freedom that > what you get with the ‘start’ and ‘stop’ fields, like: > > (shepherd-service > ;; … > (free-from #~(let ((whatever (spawn-fiber …))) > (service '(foo) #:start …)))) > > It’s probably going to be a relatively marginal use case, but it’s good > to have that extra level of flexibility. > > WDYT? Thanks for the extra explanation and example. The extra flexibility sounds good to me! Reviewed-by: Maxim Cournoyer <maxim.cournoyer@gmail>
Maxim Cournoyer <maxim.cournoyer@gmail.com> skribis: > Thanks for the extra explanation and example. The extra flexibility > sounds good to me! > > Reviewed-by: Maxim Cournoyer <maxim.cournoyer@gmail> Pushed as 0a220c1599613b7bee38c0bf8bc1bb3e9cbcaeb8, thanks! Ludo’.
diff --git a/doc/guix.texi b/doc/guix.texi index 0102fd0fad3..4d9145445cc 100644 --- a/doc/guix.texi +++ b/doc/guix.texi @@ -43909,7 +43909,7 @@ Shepherd Services When true, this is the delay in seconds before restarting a failed service. -@item @code{start} +@item @code{start} (default: @code{#~(const #t)}) @itemx @code{stop} (default: @code{#~(const #f)}) The @code{start} and @code{stop} fields refer to the Shepherd's facilities to start and stop processes (@pxref{Service De- and @@ -43928,6 +43928,30 @@ Shepherd Services herd @var{action} @var{service} [@var{arguments}@dots{}] @end example +@item @code{free-form} (default: @code{#f}) +When set, this field replaces the @code{start}, @code{stop}, and +@code{actions} fields. It is meant to be used when the service +definition comes from some other source, typically the service +collection provided by the Shepherd proper (@pxref{Service Collection,,, +shepherd, The GNU Shepherd Manual}). + +@cindex REPL service, for shepherd +For example, the snippet below defines a service for the Shepherd's +built-in @acronym{REPL, read-eval-print loop} service (@pxref{REPL +Service,,, shepherd, The GNU Shepherd Manual}): + +@lisp +(shepherd-service + (provision '(repl)) + (modules '((shepherd service repl))) + (free-form #~(repl-service))) +@end lisp + +In this case, the service object is returned by the @code{repl-service} +procedure of the Shepherd, so all the @code{free-form} G-expression does +is call that procedure. Note that the @code{provision} field must be +consistent with the actual service provision. + @item @code{auto-start?} (default: @code{#t}) Whether this service should be started automatically by the Shepherd. If it is @code{#f} the service has to be started manually with @code{herd start}. diff --git a/gnu/services/shepherd.scm b/gnu/services/shepherd.scm index ccc8e61a33c..05534ab3173 100644 --- a/gnu/services/shepherd.scm +++ b/gnu/services/shepherd.scm @@ -60,6 +60,7 @@ (define-module (gnu services shepherd) shepherd-service-respawn? shepherd-service-start shepherd-service-stop + shepherd-service-free-form shepherd-service-auto-start? shepherd-service-modules @@ -217,7 +218,10 @@ (define-record-type* <shepherd-service> (default #f)) (respawn-delay shepherd-service-respawn-delay (default #f)) - (start shepherd-service-start) ;g-expression (procedure) + (free-form shepherd-service-free-form ;#f | g-expression (service) + (default #f)) + (start shepherd-service-start ;g-expression (procedure) + (default #~(const #t))) (stop shepherd-service-stop ;g-expression (procedure) (default #~(const #f))) (actions shepherd-service-actions ;list of <shepherd-action> @@ -298,8 +302,8 @@ (define (shepherd-service-file-name service) provisions) ".scm"))) -(define (shepherd-service-file service) - "Return a file defining SERVICE." +(define (shepherd-service-file/regular service) + "Return a file defining SERVICE, a service whose 'free-form' field is #f." (scheme-file (shepherd-service-file-name service) (with-imported-modules %default-imported-modules #~(begin @@ -332,6 +336,21 @@ (define (shepherd-service-file service) #~(#$name #$doc #$proc))) (shepherd-service-actions service)))))))) +(define (shepherd-service-file/free-form service) + "Return a file defining SERVICE, a service whose 'free-form' field is set." + (scheme-file (shepherd-service-file-name service) + (with-imported-modules %default-imported-modules + #~(begin + (use-modules #$@(shepherd-service-modules service)) + + #$(shepherd-service-free-form service))))) + +(define (shepherd-service-file service) + "Return a file defining SERVICE." + (if (shepherd-service-free-form service) + (shepherd-service-file/free-form service) + (shepherd-service-file/regular service))) + (define (scm->go file shepherd) "Compile FILE, which contains code to be loaded by shepherd's config file, and return the resulting '.go' file. SHEPHERD is used as shepherd package."