services: mcron: Add 'schedule' action.
Inspired by <https://lists.gnu.org/archive/html/help-guix/2018-07/msg00035.html>. * gnu/services/mcron.scm (shepherd-schedule-action): New procedure. (mcron-shepherd-services): Add 'actions' field. * gnu/tests/base.scm (run-mcron-test)["schedule action"]: New test. * doc/guix.texi (Scheduled Job Execution): Mention 'herd schedule'.
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Ludovic Courtès
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@ -10850,6 +10850,21 @@ gexps to introduce job definitions that are passed to mcron
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for more information on mcron job specifications. Below is the
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reference of the mcron service.
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On a running system, you can use the @code{schedule} action of the service to
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visualize the mcron jobs that will be executed next:
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@example
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# herd schedule mcron
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@end example
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@noindent
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The example above lists the next five tasks that will be executed, but you can
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also specify the number of tasks to display:
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@example
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# herd schedule mcron 10
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@end example
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@deffn {Scheme Procedure} mcron-service @var{jobs} [#:mcron @var{mcron}]
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Return an mcron service running @var{mcron} that schedules @var{jobs}, a
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list of gexps denoting mcron job specifications.
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@ -45,6 +45,7 @@
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live-service-requirement
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live-service-running
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with-shepherd-action
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current-services
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unload-services
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unload-service
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@ -168,6 +169,8 @@ return #f."
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(define-syntax-rule (with-shepherd-action service (action args ...)
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result body ...)
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"Invoke ACTION on SERVICE with the given ARGS, and evaluate BODY with RESULT
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bound to the action's result."
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(invoke-action service action (list args ...)
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(lambda (result) body ...)))
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@ -60,29 +60,71 @@
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(define (job-file job)
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(scheme-file "mcron-job" job))
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(define (shepherd-schedule-action mcron files)
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"Return a Shepherd action that runs MCRON with '--schedule' for the given
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files."
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(shepherd-action
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(name 'schedule)
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(documentation
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"Display jobs that are going to be scheduled.")
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(procedure
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#~(lambda* (_ #:optional (n "5"))
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;; XXX: This is a global side effect.
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(setenv "GUILE_AUTO_COMPILE" "0")
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;; Run 'mcron' in a pipe so we can explicitly redirect its output to
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;; 'current-output-port', which at this stage is bound to the client
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;; connection.
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(let ((pipe (open-pipe* OPEN_READ
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#$(file-append mcron "/bin/mcron")
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(string-append "--schedule=" n)
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#$@files)))
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(let loop ()
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(match (read-line pipe 'concat)
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((? eof-object?)
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(catch 'system-error
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(lambda ()
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(zero? (close-pipe pipe)))
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(lambda args
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;; There's with race between the SIGCHLD handler, which
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;; could call 'waitpid' before 'close-pipe' above does. If
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;; we get ECHILD, that means we lost the race, but that's
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;; fine.
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(or (= ECHILD (system-error-errno args))
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(apply throw args)))))
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(line
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(display line)
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(loop)))))))))
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(define mcron-shepherd-services
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(match-lambda
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(($ <mcron-configuration> mcron ()) ;nothing to do!
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'())
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(($ <mcron-configuration> mcron jobs)
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(list (shepherd-service
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(provision '(mcron))
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(requirement '(user-processes))
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(modules `((srfi srfi-1)
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(srfi srfi-26)
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,@%default-modules))
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(start #~(make-forkexec-constructor
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(list (string-append #$mcron "/bin/mcron")
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#$@(map job-file jobs))
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(let ((files (map job-file jobs)))
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(list (shepherd-service
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(provision '(mcron))
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(requirement '(user-processes))
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(modules `((srfi srfi-1)
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(srfi srfi-26)
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(ice-9 popen) ;for the 'schedule' action
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(ice-9 rdelim)
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(ice-9 match)
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,@%default-modules))
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(start #~(make-forkexec-constructor
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(list (string-append #$mcron "/bin/mcron") #$@files)
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;; Disable auto-compilation of the job files and set a
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;; sane value for 'PATH'.
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#:environment-variables
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(cons* "GUILE_AUTO_COMPILE=0"
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"PATH=/run/current-system/profile/bin"
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(remove (cut string-prefix? "PATH=" <>)
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(environ)))))
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(stop #~(make-kill-destructor)))))))
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;; Disable auto-compilation of the job files and set a
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;; sane value for 'PATH'.
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#:environment-variables
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(cons* "GUILE_AUTO_COMPILE=0"
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"PATH=/run/current-system/profile/bin"
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(remove (cut string-prefix? "PATH=" <>)
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(environ)))))
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(stop #~(make-kill-destructor))
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(actions
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(list (shepherd-schedule-action mcron files)))))))))
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(define mcron-service-type
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(service-type (name 'mcron)
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@ -632,6 +632,13 @@ non-ASCII names from /tmp.")
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(wait-for-file "/root/witness-touch" marionette
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#:read '(@ (ice-9 rdelim) read-string)))
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;; Make sure the 'schedule' action is accepted.
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(test-equal "schedule action"
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'(#t) ;one value, #t
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(marionette-eval '(with-shepherd-action 'mcron ('schedule) result
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result)
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marionette))
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(test-end)
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(exit (= (test-runner-fail-count (test-runner-current)) 0)))))
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