701383081a
* gnu/services/shepherd.scm (<shepherd-service>)[actions]: New field. (<shepherd-action>): New record type. (shepherd-service-file): Pass #:actions to 'make'. * doc/guix.texi (Shepherd Services): Document custom actions.
378 lines
15 KiB
Scheme
378 lines
15 KiB
Scheme
;;; GNU Guix --- Functional package management for GNU
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;;; Copyright © 2013, 2014, 2015, 2016, 2018 Ludovic Courtès <ludo@gnu.org>
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;;; Copyright © 2017 Clément Lassieur <clement@lassieur.org>
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;;;
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;;; This file is part of GNU Guix.
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;;;
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;;; GNU Guix is free software; you can redistribute it and/or modify it
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;;; under the terms of the GNU General Public License as published by
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;;; the Free Software Foundation; either version 3 of the License, or (at
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;;; your option) any later version.
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;;;
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;;; GNU Guix is distributed in the hope that it will be useful, but
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;;; WITHOUT ANY WARRANTY; without even the implied warranty of
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;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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;;; GNU General Public License for more details.
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;;;
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;;; You should have received a copy of the GNU General Public License
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;;; along with GNU Guix. If not, see <http://www.gnu.org/licenses/>.
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(define-module (gnu services shepherd)
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#:use-module (guix ui)
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#:use-module (guix sets)
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#:use-module (guix gexp)
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#:use-module (guix store)
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#:use-module (guix records)
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#:use-module (guix derivations) ;imported-modules, etc.
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#:use-module (gnu services)
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#:use-module (gnu services herd)
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#:use-module (gnu packages admin)
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#:use-module (ice-9 match)
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#:use-module (ice-9 vlist)
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#:use-module (srfi srfi-1)
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#:use-module (srfi srfi-26)
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#:use-module (srfi srfi-34)
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#:use-module (srfi srfi-35)
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#:export (shepherd-root-service-type
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%shepherd-root-service
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shepherd-service-type
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shepherd-service
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shepherd-service?
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shepherd-service-documentation
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shepherd-service-provision
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shepherd-service-canonical-name
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shepherd-service-requirement
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shepherd-service-respawn?
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shepherd-service-start
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shepherd-service-stop
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shepherd-service-auto-start?
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shepherd-service-modules
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shepherd-action
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shepherd-action?
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shepherd-action-name
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shepherd-action-documentation
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shepherd-action-procedure
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%default-modules
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shepherd-service-file
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shepherd-service-lookup-procedure
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shepherd-service-back-edges
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shepherd-service-upgrade))
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;;; Commentary:
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;;;
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;;; Instantiating system services as a shepherd configuration file.
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;;;
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;;; Code:
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(define (shepherd-boot-gexp services)
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#~(begin
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;; Keep track of the booted system.
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(false-if-exception (delete-file "/run/booted-system"))
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(symlink (readlink "/run/current-system")
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"/run/booted-system")
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;; Close any remaining open file descriptors to be on the safe
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;; side. This must be the very last thing we do, because
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;; Guile has internal FDs such as 'sleep_pipe' that need to be
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;; alive.
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(let loop ((fd 3))
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(when (< fd 1024)
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(false-if-exception (close-fdes fd))
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(loop (+ 1 fd))))
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;; Start shepherd.
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(execl #$(file-append shepherd "/bin/shepherd")
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"shepherd" "--config"
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#$(shepherd-configuration-file services))))
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(define shepherd-root-service-type
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(service-type
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(name 'shepherd-root)
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;; Extending the root shepherd service (aka. PID 1) happens by
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;; concatenating the list of services provided by the extensions.
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(compose concatenate)
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(extend append)
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(extensions (list (service-extension boot-service-type
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shepherd-boot-gexp)
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(service-extension profile-service-type
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(const (list shepherd)))))))
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(define %shepherd-root-service
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;; The root shepherd service, aka. PID 1. Its parameter is a list of
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;; <shepherd-service> objects.
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(service shepherd-root-service-type '()))
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(define-syntax shepherd-service-type
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(syntax-rules ()
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"Return a <service-type> denoting a simple shepherd service--i.e., the type
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for a service that extends SHEPHERD-ROOT-SERVICE-TYPE and nothing else. When
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DEFAULT is given, use it as the service's default value."
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((_ service-name proc default)
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(service-type
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(name service-name)
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(extensions
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(list (service-extension shepherd-root-service-type
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(compose list proc))))
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(default-value default)))
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((_ service-name proc)
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(service-type
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(name service-name)
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(extensions
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(list (service-extension shepherd-root-service-type
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(compose list proc))))))))
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(define %default-imported-modules
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;; Default set of modules imported for a service's consumption.
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'((guix build utils)
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(guix build syscalls)))
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(define %default-modules
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;; Default set of modules visible in a service's file.
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`((shepherd service)
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(oop goops)
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(guix build utils)
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(guix build syscalls)))
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(define-record-type* <shepherd-service>
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shepherd-service make-shepherd-service
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shepherd-service?
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(documentation shepherd-service-documentation ;string
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(default "[No documentation.]"))
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(provision shepherd-service-provision) ;list of symbols
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(requirement shepherd-service-requirement ;list of symbols
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(default '()))
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(respawn? shepherd-service-respawn? ;Boolean
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(default #t))
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(start shepherd-service-start) ;g-expression (procedure)
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(stop shepherd-service-stop ;g-expression (procedure)
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(default #~(const #f)))
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(actions shepherd-service-actions ;list of <shepherd-action>
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(default '()))
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(auto-start? shepherd-service-auto-start? ;Boolean
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(default #t))
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(modules shepherd-service-modules ;list of module names
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(default %default-modules)))
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(define-record-type* <shepherd-action>
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shepherd-action make-shepherd-action
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shepherd-action?
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(name shepherd-action-name) ;symbol
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(procedure shepherd-action-procedure) ;gexp
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(documentation shepherd-action-documentation)) ;string
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(define (shepherd-service-canonical-name service)
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"Return the 'canonical name' of SERVICE."
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(first (shepherd-service-provision service)))
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(define (assert-valid-graph services)
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"Raise an error if SERVICES does not define a valid shepherd service graph,
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for instance if a service requires a nonexistent service, or if more than one
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service uses a given name.
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These are constraints that shepherd's 'register-service' verifies but we'd
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better verify them here statically than wait until PID 1 halts with an
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assertion failure."
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(define provisions
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;; The set of provisions (symbols). Bail out if a symbol is given more
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;; than once.
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(fold (lambda (service set)
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(define (assert-unique symbol)
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(when (set-contains? set symbol)
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(raise (condition
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(&message
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(message
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(format #f (G_ "service '~a' provided more than once")
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symbol)))))))
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(for-each assert-unique (shepherd-service-provision service))
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(fold set-insert set (shepherd-service-provision service)))
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(setq 'shepherd)
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services))
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(define (assert-satisfied-requirements service)
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;; Bail out if the requirements of SERVICE aren't satisfied.
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(for-each (lambda (requirement)
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(unless (set-contains? provisions requirement)
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(raise (condition
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(&message
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(message
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(format #f (G_ "service '~a' requires '~a', \
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which is not provided by any service")
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(match (shepherd-service-provision service)
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((head . _) head)
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(_ service))
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requirement)))))))
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(shepherd-service-requirement service)))
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(for-each assert-satisfied-requirements services))
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(define (shepherd-service-file-name service)
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"Return the file name where the initialization code for SERVICE is to be
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stored."
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(let ((provisions (string-join (map symbol->string
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(shepherd-service-provision service)))))
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(string-append "shepherd-"
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(string-map (match-lambda
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(#\/ #\-)
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(#\ #\-)
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(chr chr))
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provisions)
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".scm")))
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(define (shepherd-service-file service)
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"Return a file defining SERVICE."
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(scheme-file (shepherd-service-file-name service)
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(with-imported-modules %default-imported-modules
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#~(begin
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(use-modules #$@(shepherd-service-modules service))
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(make <service>
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#:docstring '#$(shepherd-service-documentation service)
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#:provides '#$(shepherd-service-provision service)
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#:requires '#$(shepherd-service-requirement service)
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#:respawn? '#$(shepherd-service-respawn? service)
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#:start #$(shepherd-service-start service)
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#:stop #$(shepherd-service-stop service)
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#:actions
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(make-actions
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#$@(map (match-lambda
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(($ <shepherd-action> name proc doc)
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#~(#$name #$doc #$proc)))
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(shepherd-service-actions service))))))))
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(define (shepherd-configuration-file services)
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"Return the shepherd configuration file for SERVICES."
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(assert-valid-graph services)
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(let ((files (map shepherd-service-file services)))
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(define config
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#~(begin
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(use-modules (srfi srfi-34)
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(system repl error-handling))
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;; Arrange to spawn a REPL if something goes wrong. This is better
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;; than a kernel panic.
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(call-with-error-handling
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(lambda ()
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(apply register-services (map primitive-load '#$files))
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;; guix-daemon 0.6 aborts if 'PATH' is undefined, so work around
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;; it.
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(setenv "PATH" "/run/current-system/profile/bin")
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(format #t "starting services...~%")
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(for-each (lambda (service)
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;; In the Shepherd 0.3 the 'start' method can raise
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;; '&action-runtime-error' if it fails, so protect
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;; against it. (XXX: 'action-runtime-error?' is not
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;; exported is 0.3, hence 'service-error?'.)
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(guard (c ((service-error? c)
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(format (current-error-port)
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"failed to start service '~a'~%"
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service)))
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(start service)))
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'#$(append-map shepherd-service-provision
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(filter shepherd-service-auto-start?
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services)))))))
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(scheme-file "shepherd.conf" config)))
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(define* (shepherd-service-lookup-procedure services
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#:optional
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(provision
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shepherd-service-provision))
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"Return a procedure that, when passed a symbol, return the item among
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SERVICES that provides this symbol. PROVISION must be a one-argument
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procedure that takes a service and returns the list of symbols it provides."
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(let ((services (fold (lambda (service result)
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(fold (cut vhash-consq <> service <>)
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result
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(provision service)))
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vlist-null
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services)))
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(lambda (name)
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(match (vhash-assq name services)
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((_ . service) service)
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(#f #f)))))
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(define* (shepherd-service-back-edges services
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#:key
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(provision shepherd-service-provision)
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(requirement shepherd-service-requirement))
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"Return a procedure that, when given a <shepherd-service> from SERVICES,
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returns the list of <shepherd-service> that depend on it.
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Use PROVISION and REQUIREMENT as one-argument procedures that return the
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symbols provided/required by a service."
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(define provision->service
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(shepherd-service-lookup-procedure services provision))
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(define edges
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(fold (lambda (service edges)
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(fold (lambda (requirement edges)
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(vhash-consq (provision->service requirement) service
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edges))
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edges
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(requirement service)))
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vlist-null
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services))
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(lambda (service)
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(vhash-foldq* cons '() service edges)))
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(define (shepherd-service-upgrade live target)
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"Return two values: the subset of LIVE (a list of <live-service>) that needs
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to be unloaded, and the subset of TARGET (a list of <shepherd-service>) that
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needs to be loaded."
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(define (essential? service)
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(memq (first (live-service-provision service))
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'(root shepherd)))
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(define lookup-target
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(shepherd-service-lookup-procedure target
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shepherd-service-provision))
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(define lookup-live
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(shepherd-service-lookup-procedure live
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live-service-provision))
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(define (running? service)
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(and=> (lookup-live (shepherd-service-canonical-name service))
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live-service-running))
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(define (stopped service)
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(match (lookup-live (shepherd-service-canonical-name service))
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(#f #f)
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(service (and (not (live-service-running service))
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service))))
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(define live-service-dependents
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(shepherd-service-back-edges live
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#:provision live-service-provision
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#:requirement live-service-requirement))
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(define (obsolete? service)
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(match (lookup-target (first (live-service-provision service)))
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(#f (every obsolete? (live-service-dependents service)))
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(_ #f)))
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(define to-load
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;; Only load services that are either new or currently stopped.
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(remove running? target))
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(define to-unload
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;; Unload services that are (1) no longer required, or (2) are in TO-LOAD.
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(remove essential?
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(append (filter obsolete? live)
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(filter-map stopped to-load))))
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(values to-unload to-load))
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;;; shepherd.scm ends here
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