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services: Missing services are automatically instantiated. 

This simplifies OS configuration: users no longer need to be aware of
what a given service depends on.

See the discussion at
<https://lists.gnu.org/archive/html/guix-devel/2018-01/msg00114.html>.

* gnu/services.scm (missing-target-error): New procedure.
(service-back-edges): Use it.
(instantiate-missing-services): New procedure.
* gnu/system.scm (operating-system-services): Call
'instantiate-missing-services'.
* tests/services.scm ("instantiate-missing-services")
("instantiate-missing-services, no default value"): New tests.
* gnu/services/version-control.scm (cgit-service-type)[extensions]: Add
FCGIWRAP-SERVICE-TYPE.
* gnu/tests/version-control.scm (%cgit-os): Remove NGINX-SERVICE-TYPE
and FCGIWRAP-SERVICE-TYPE instances.
* doc/guix.texi (Log Rotation): Remove 'mcron-service-type' in example.
(Miscellaneous Services): Remove 'nginx-service-type' and
'fcgiwrap-service-type' in Cgit example.
This commit is contained in:
Ludovic Courtès 2018-01-21 00:05:09 +01:00
parent bc58201ec2
commit d466b1fc82
No known key found for this signature in database
GPG Key ID: 090B11993D9AEBB5
6 changed files with 90 additions and 23 deletions
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5
doc/guix.texi
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@ -10342,8 +10342,7 @@ with the default settings, for commonly encountered log files.
(operating-system
;; @dots{}
(services (cons* (service mcron-service-type)
(service rottlog-service-type)
(services (cons (service rottlog-service-type)
%base-services)))
@end lisp
@ -18269,8 +18268,6 @@ The following example will configure the service with default values.
By default, Cgit can be accessed on port 80 (@code{http://localhost:80}).
@example
(service nginx-service-type)
(service fcgiwrap-service-type)
(service cgit-service-type)
@end example

59
gnu/services.scm
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@ -1,5 +1,5 @@
;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2015, 2016, 2017 Ludovic Courtès <ludo@gnu.org>
;;; Copyright © 2015, 2016, 2017, 2018 Ludovic Courtès <ludo@gnu.org>
;;; Copyright © 2016 Chris Marusich <cmmarusich@gmail.com>
;;;
;;; This file is part of GNU Guix.
@ -24,6 +24,7 @@
#:use-module (guix records)
#:use-module (guix profiles)
#:use-module (guix discovery)
#:use-module (guix combinators)
#:use-module (guix sets)
#:use-module (guix ui)
#:use-module ((guix utils) #:select (source-properties->location))
@ -66,6 +67,7 @@
simple-service
modify-services
service-back-edges
instantiate-missing-services
fold-services
service-error?
@ -630,6 +632,18 @@ kernel."
(service ambiguous-target-service-error-service)
(target-type ambiguous-target-service-error-target-type))
(define (missing-target-error service target-type)
(raise
(condition (&missing-target-service-error
(service service)
(target-type target-type))
(&message
(message
(format #f (G_ "no target of type '~a' for service '~a'")
(service-type-name target-type)
(service-type-name
(service-kind service))))))))
(define (service-back-edges services)
"Return a procedure that, when passed a <service>, returns the list of
<service> objects that depend on it."
@ -642,16 +656,7 @@ kernel."
((target)
(vhash-consq target service edges))
(()
(raise
(condition (&missing-target-service-error
(service service)
(target-type target-type))
(&message
(message
(format #f (G_ "no target of type '~a' for service '~a'")
(service-type-name target-type)
(service-type-name
(service-kind service))))))))
(missing-target-error service target-type))
(x
(raise
(condition (&ambiguous-target-service-error
@ -669,6 +674,38 @@ kernel."
(lambda (node)
(reverse (vhash-foldq* cons '() node edges)))))
(define (instantiate-missing-services services)
"Return SERVICES, a list, augmented with any services targeted by extensions
and missing from SERVICES. Only service types with a default value can be
instantiated; other missing services lead to a
'&missing-target-service-error'."
(define (adjust-service-list svc result instances)
(fold2 (lambda (extension result instances)
(define target-type
(service-extension-target extension))
(match (vhash-assq target-type instances)
(#f
(let ((default (service-type-default-value target-type)))
(if (eq? &no-default-value default)
(missing-target-error svc target-type)
(let ((new (service target-type)))
(values (cons new result)
(vhash-consq target-type new instances))))))
(_
(values result instances))))
result
instances
(service-type-extensions (service-kind svc))))
(let ((instances (fold (lambda (service result)
(vhash-consq (service-kind service) service
result))
vlist-null services)))
(fold2 adjust-service-list
services instances
services)))
(define* (fold-services services
#:key (target-type system-service-type))
"Fold SERVICES by propagating their extensions down to the root of type

6
gnu/services/version-control.scm
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@ -263,7 +263,11 @@ access to exported repositories under @file{/srv/git}."
(list (service-extension activation-service-type
cgit-activation)
(service-extension nginx-service-type
cgit-configuration-nginx-config)))
cgit-configuration-nginx-config)
;; Make sure fcgiwrap is instantiated.
(service-extension fcgiwrap-service-type
(const #t))))
(default-value (cgit-configuration))
(description
"Run the Cgit web interface, which allows users to browse Git

5
gnu/system.scm
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@ -1,5 +1,5 @@
;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2013, 2014, 2015, 2016, 2017 Ludovic Courtès <ludo@gnu.org>
;;; Copyright © 2013, 2014, 2015, 2016, 2017, 2018 Ludovic Courtès <ludo@gnu.org>
;;; Copyright © 2015 Mark H Weaver <mhw@netris.org>
;;; Copyright © 2015, 2016 Alex Kost <alezost@gmail.com>
;;; Copyright © 2016 Chris Marusich <cmmarusich@gmail.com>
@ -492,8 +492,9 @@ a container or that of a \"bare metal\" system."
(define* (operating-system-services os #:key container?)
"Return all the services of OS, including \"internal\" services that do not
explicitly appear in OS."
(instantiate-missing-services
(append (operating-system-user-services os)
(essential-services os #:container? container?)))
(essential-services os #:container? container?))))
;;;

2
gnu/tests/version-control.scm
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@ -88,8 +88,6 @@
(let ((base-os
(simple-operating-system
(dhcp-client-service)
(service nginx-service-type)
(service fcgiwrap-service-type)
(service cgit-service-type
(cgit-configuration
(nginx %cgit-configuration-nginx)))

32
tests/services.scm
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@ -1,5 +1,5 @@
;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2015, 2016, 2017 Ludovic Courtès <ludo@gnu.org>
;;; Copyright © 2015, 2016, 2017, 2018 Ludovic Courtès <ludo@gnu.org>
;;;
;;; This file is part of GNU Guix.
;;;
@ -122,6 +122,36 @@
(fold-services (list s) #:target-type t1)
#f)))
(test-assert "instantiate-missing-services"
(let* ((t1 (service-type (name 't1) (extensions '())
(default-value 'dflt)
(compose concatenate)
(extend cons)))
(t2 (service-type (name 't2)
(extensions
(list (service-extension t1 list)))))
(s1 (service t1 'hey!))
(s2 (service t2 42)))
(and (lset= equal?
(list (service t1) s2)
(instantiate-missing-services (list s2)))
(equal? (list s1 s2)
(instantiate-missing-services (list s1 s2))))))
(test-assert "instantiate-missing-services, no default value"
(let* ((t1 (service-type (name 't1) (extensions '())))
(t2 (service-type (name 't2)
(extensions
(list (service-extension t1 list)))))
(s (service t2 42)))
(guard (c ((missing-target-service-error? c)
(and (eq? (missing-target-service-error-target-type c)
t1)
(eq? (missing-target-service-error-service c)
s))))
(instantiate-missing-services (list s))
#f)))
(test-assert "shepherd-service-lookup-procedure"
(let* ((s1 (shepherd-service (provision '(s1 s1b)) (start #f)))
(s2 (shepherd-service (provision '(s2 s2b)) (start #f)))