services: mcron: Add log? and log-format fields to mcron-configuration.

* gnu/services/mcron.scm (list-of-gexps?): New predicate.
(mcron-configuration): Rewrite using define-configuration.
[log?, log-format]: New fields.
(mcron-shepherd-services): Invoke mcron with the --log and --log-format
arguments when log? is #t,
(generate-doc): New procedure.
* doc/guix.texi (Scheduled Job Execution): Update doc.
(Mcron Home Service): Likewise.
* gnu/home/services/mcron.scm: Keep in sync with the above changes to
gnu/services/mcron.scm.

1 files changed, 36 insertions, 11 deletions

diff --git a/gnu/services/mcron.scm b/gnu/services/mcron.scm
index 23760ebda4..52332d6123 100644
--- a/gnu/services/mcron.scm
+++ b/gnu/services/mcron.scm
@@ -1,5 +1,6 @@
 ;;; GNU Guix --- Functional package management for GNU
 ;;; Copyright © 2016, 2017, 2018, 2019, 2020 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2022 Maxim Cournoyer <maxim.cournoyer@gmail.com>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -18,6 +19,7 @@
 
 (define-module (gnu services mcron)
   #:use-module (gnu services)
+  #:use-module (gnu services configuration)
   #:use-module (gnu services shepherd)
   #:use-module (gnu packages guile-xyz)
   #:use-module (guix deprecation)
@@ -30,6 +32,8 @@
             mcron-configuration?
             mcron-configuration-mcron
             mcron-configuration-jobs
+            mcron-configuration-log?
+            mcron-configuration-log-format
 
             mcron-service-type))
 
@@ -48,13 +52,23 @@
 ;;;
 ;;; Code:
 
-(define-record-type* <mcron-configuration> mcron-configuration
-  make-mcron-configuration
-  mcron-configuration?
-  (mcron             mcron-configuration-mcron    ;file-like
-                     (default mcron))
-  (jobs              mcron-configuration-jobs     ;list of <mcron-job>
-                     (default '())))
+(define list-of-gexps?
+  (list-of gexp?))
+
+(define-configuration/no-serialization mcron-configuration
+  (mcron (file-like mcron) "The mcron package to use.")
+  (jobs
+   (list-of-gexps '())
+   "This is a list of gexps (@pxref{G-Expressions}), where each gexp
+corresponds to an mcron job specification (@pxref{Syntax, mcron job
+specifications,, mcron, GNU@tie{}mcron}).")
+  (log? (boolean #t) "Log messages to standard output.")
+  (log-format
+   (string "~1@*~a ~a: ~a~%")
+   "@code{(ice-9 format)} format string for log messages.  The default value
+produces messages like \"@samp{@var{pid} @var{name}:
+@var{message}\"} (@pxref{Invoking mcron, Invoking,, mcron, GNU@tie{}mcron}).
+Each message is also prefixed by a timestamp by GNU Shepherd."))
 
 (define (job-files mcron jobs)
   "Return a list of file-like object for JOBS, a list of gexps."
@@ -124,21 +138,25 @@ files."
 
 (define mcron-shepherd-services
   (match-lambda
-    (($ <mcron-configuration> mcron ())           ;nothing to do!
+    (($ <mcron-configuration> mcron ()) ;nothing to do!
      '())
-    (($ <mcron-configuration> mcron jobs)
+    (($ <mcron-configuration> mcron jobs log? log-format)
      (let ((files (job-files mcron jobs)))
        (list (shepherd-service
               (provision '(mcron))
               (requirement '(user-processes))
               (modules `((srfi srfi-1)
                          (srfi srfi-26)
-                         (ice-9 popen)            ;for the 'schedule' action
+                         (ice-9 popen)  ;for the 'schedule' action
                          (ice-9 rdelim)
                          (ice-9 match)
                          ,@%default-modules))
               (start #~(make-forkexec-constructor
-                        (list (string-append #$mcron "/bin/mcron") #$@files)
+                        (list (string-append #$mcron "/bin/mcron")
+                              #$@(if log?
+                                     #~("--log" "--log-format" #$log-format)
+                                     #~())
+                              #$@files)
 
                         ;; Disable auto-compilation of the job files and set a
                         ;; sane value for 'PATH'.
@@ -172,4 +190,11 @@ files."
                                          jobs)))))
                 (default-value (mcron-configuration)))) ;empty job list
 
+
+;;;
+;;; Generate documentation.
+;;;
+(define (generate-doc)
+  (configuration->documentation 'mcron-configuration))
+
 ;;; mcron.scm ends here