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;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2016 Ludovic Courtès <ludo@gnu.org>
;;;
;;; This file is part of GNU Guix.
;;;
;;; GNU Guix is free software; you can redistribute it and/or modify it
;;; under the terms of the GNU General Public License as published by
;;; the Free Software Foundation; either version 3 of the License, or (at
;;; your option) any later version.
;;;
;;; GNU Guix is distributed in the hope that it will be useful, but
;;; WITHOUT ANY WARRANTY; without even the implied warranty of
;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
;;; GNU General Public License for more details.
;;;
;;; You should have received a copy of the GNU General Public License
;;; along with GNU Guix. If not, see <http://www.gnu.org/licenses/>.
(define-module (gnu services herd)
#:use-module (guix ui)
#:use-module (guix utils)
#:use-module (srfi srfi-1)
#:use-module (srfi srfi-11)
#:use-module (ice-9 match)
#:export (current-services
unload-services
unload-service
load-services
start-service))
;;; Commentary:
;;;
;;; This module provides an interface to the GNU Shepherd, similar to the
;;; 'herd' command. Essentially it implements a subset of the (shepherd comm)
;;; module, but focusing only on the parts relevant to 'guix system
;;; reconfigure'.
;;;
;;; Code:
(define %shepherd-socket-file
"/var/run/shepherd/socket")
(define* (open-connection #:optional (file %shepherd-socket-file))
"Open a connection to the daemon, using the Unix-domain socket at FILE, and
return the socket."
;; The protocol is sexp-based and UTF-8-encoded.
(with-fluids ((%default-port-encoding "UTF-8"))
(let ((sock (socket PF_UNIX SOCK_STREAM 0))
(address (make-socket-address PF_UNIX file)))
(catch 'system-error
(lambda ()
(connect sock address)
(setvbuf sock _IOFBF 1024)
sock)
(lambda args
(close-port sock)
(apply throw args))))))
(define-syntax-rule (with-shepherd connection body ...)
"Evaluate BODY... with CONNECTION bound to an open socket to PID 1."
(let ((connection (open-connection)))
body ...))
(define (report-action-error error)
"Report ERROR, an sexp received by a shepherd client in reply to COMMAND, a
command object."
(match error
(('error ('version 0 x ...) 'service-not-found service)
(report-error (_ "service '~a' could not be found")
service))
(('error ('version 0 x ...) 'action-not-found action service)
(report-error (_ "service '~a' does not have an action '~a'")
service action))
(('error ('version 0 x ...) 'action-exception action service
key (args ...))
(report-error (_ "exception caught while executing '~a' \
on service '~a':")
action service)
(print-exception (current-error-port) #f key args))
(('error . _)
(report-error (_ "something went wrong: ~s")
error))
(#f ;not an error
#t)))
(define (display-message message)
;; TRANSLATORS: Nothing to translate here.
(info (_ "shepherd: ~a~%") message))
(define* (invoke-action service action arguments cont)
"Invoke ACTION on SERVICE with ARGUMENTS. On success, call CONT with the
result. Otherwise return #f."
(with-shepherd sock
(write `(shepherd-command (version 0)
(action ,action)
(service ,service)
(arguments ,arguments)
(directory ,(getcwd)))
sock)
(force-output sock)
(match (read sock)
(('reply ('version 0 _ ...) ('result (result)) ('error #f)
('messages messages))
(for-each display-message messages)
(cont result))
(('reply ('version 0 x ...) ('result y) ('error error)
('messages messages))
(for-each display-message messages)
(report-action-error error)
#f)
(x
(warning (_ "invalid shepherd reply~%"))
#f))))
(define-syntax-rule (with-shepherd-action service (action args ...)
result body ...)
(invoke-action service action (list args ...)
(lambda (result) body ...)))
(define-syntax alist-let*
(syntax-rules ()
"Bind the given KEYs in EXP to the corresponding items in ALIST. ALIST
is assumed to be a list of two-element tuples rather than a traditional list
of pairs."
((_ alist (key ...) exp ...)
(let ((key (and=> (assoc-ref alist 'key) car)) ...)
exp ...))))
(define (current-services)
"Return two lists: the list of currently running services, and the list of
currently stopped services."
(with-shepherd-action 'root ('status) services
(match services
((('service ('version 0 _ ...) _ ...) ...)
(fold2 (lambda (service running-services stopped-services)
(alist-let* service (provides running)
(if running
(values (cons (first provides) running-services)
stopped-services)
(values running-services
(cons (first provides) stopped-services)))))
'()
'()
services))
(x
(warning (_ "failed to obtain list of shepherd services~%"))
(values #f #f)))))
(define (unload-service service)
"Unload SERVICE, a symbol name; return #t on success."
(with-shepherd-action 'root ('unload (symbol->string service)) result
result))
(define (%load-file file)
"Load FILE in the Shepherd."
(with-shepherd-action 'root ('load file) result
result))
(define (eval-there exp)
"Eval EXP in the Shepherd."
(with-shepherd-action 'root ('eval (object->string exp)) result
result))
(define (load-services files)
"Load and register the services from FILES, where FILES contain code that
returns a shepherd <service> object."
(eval-there `(register-services
,@(map (lambda (file)
`(primitive-load ,file))
files))))
(define (start-service name)
(with-shepherd-action name ('start) result
result))
;; Local Variables:
;; eval: (put 'alist-let* 'scheme-indent-function 2)
;; eval: (put 'with-shepherd 'scheme-indent-function 1)
;; eval: (put 'with-shepherd-action 'scheme-indent-function 3)
;; End:
;;; herd.scm ends here
|
