summary refs log tree commit diff
path: root/gnu/services/shepherd.scm
blob: 6cf15a5e004eb689f8242a76f9625396610caabe (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2013, 2014, 2015, 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 shepherd)
  #:use-module (guix ui)
  #:use-module (guix sets)
  #:use-module (guix gexp)
  #:use-module (guix store)
  #:use-module (guix monads)
  #:use-module (guix records)
  #:use-module (guix derivations)                 ;imported-modules, etc.
  #:use-module (gnu services)
  #:use-module (gnu packages admin)
  #:use-module (ice-9 match)
  #:use-module (ice-9 vlist)
  #:use-module (srfi srfi-1)
  #:use-module (srfi srfi-26)
  #:use-module (srfi srfi-34)
  #:use-module (srfi srfi-35)
  #:export (shepherd-root-service-type
            %shepherd-root-service
            shepherd-service-type

            shepherd-service
            shepherd-service?
            shepherd-service-documentation
            shepherd-service-provision
            shepherd-service-canonical-name
            shepherd-service-requirement
            shepherd-service-respawn?
            shepherd-service-start
            shepherd-service-stop
            shepherd-service-auto-start?
            shepherd-service-modules
            shepherd-service-imported-modules

            %default-imported-modules
            %default-modules

            shepherd-service-file

            shepherd-service-back-edges))

;;; Commentary:
;;;
;;; Instantiating system services as a shepherd configuration file.
;;;
;;; Code:


(define (shepherd-boot-gexp services)
  (mlet %store-monad ((shepherd-conf (shepherd-configuration-file services)))
    (return #~(begin
                ;; Keep track of the booted system.
                (false-if-exception (delete-file "/run/booted-system"))
                (symlink (readlink "/run/current-system")
                         "/run/booted-system")

                ;; Close any remaining open file descriptors to be on the safe
                ;; side.  This must be the very last thing we do, because
                ;; Guile has internal FDs such as 'sleep_pipe' that need to be
                ;; alive.
                (let loop ((fd 3))
                  (when (< fd 1024)
                    (false-if-exception (close-fdes fd))
                    (loop (+ 1 fd))))

                ;; Start shepherd.
                (execl (string-append #$shepherd "/bin/shepherd")
                       "shepherd" "--config" #$shepherd-conf)))))

(define shepherd-root-service-type
  (service-type
   (name 'shepherd-root)
   ;; Extending the root shepherd service (aka. PID 1) happens by
   ;; concatenating the list of services provided by the extensions.
   (compose concatenate)
   (extend append)
   (extensions (list (service-extension boot-service-type
                                        shepherd-boot-gexp)
                     (service-extension profile-service-type
                                        (const (list shepherd)))))))

(define %shepherd-root-service
  ;; The root shepherd service, aka. PID 1.  Its parameter is a list of
  ;; <shepherd-service> objects.
  (service shepherd-root-service-type '()))

(define-syntax-rule (shepherd-service-type service-name proc)
  "Return a <service-type> denoting a simple shepherd service--i.e., the type
for a service that extends SHEPHERD-ROOT-SERVICE-TYPE and nothing else."
  (service-type
   (name service-name)
   (extensions
    (list (service-extension shepherd-root-service-type
                             (compose list proc))))))

(define %default-imported-modules
  ;; Default set of modules imported for a service's consumption.
  '((guix build utils)
    (guix build syscalls)))

(define %default-modules
  ;; Default set of modules visible in a service's file.
  `((shepherd service)
    (oop goops)
    (guix build utils)
    (guix build syscalls)))

(define-record-type* <shepherd-service>
  shepherd-service make-shepherd-service
  shepherd-service?
  (documentation shepherd-service-documentation        ;string
                 (default "[No documentation.]"))
  (provision     shepherd-service-provision)           ;list of symbols
  (requirement   shepherd-service-requirement          ;list of symbols
                 (default '()))
  (respawn?      shepherd-service-respawn?             ;Boolean
                 (default #t))
  (start         shepherd-service-start)               ;g-expression (procedure)
  (stop          shepherd-service-stop                 ;g-expression (procedure)
                 (default #~(const #f)))
  (auto-start?   shepherd-service-auto-start?          ;Boolean
                 (default #t))
  (modules       shepherd-service-modules              ;list of module names
                 (default %default-modules))
  (imported-modules shepherd-service-imported-modules  ;list of module names
                    (default %default-imported-modules)))

(define (shepherd-service-canonical-name service)
  "Return the 'canonical name' of SERVICE."
  (first (shepherd-service-provision service)))

(define (assert-valid-graph services)
  "Raise an error if SERVICES does not define a valid shepherd service graph,
for instance if a service requires a nonexistent service, or if more than one
service uses a given name.

These are constraints that shepherd's 'register-service' verifies but we'd
better verify them here statically than wait until PID 1 halts with an
assertion failure."
  (define provisions
    ;; The set of provisions (symbols).  Bail out if a symbol is given more
    ;; than once.
    (fold (lambda (service set)
            (define (assert-unique symbol)
              (when (set-contains? set symbol)
                (raise (condition
                        (&message
                         (message
                          (format #f (_ "service '~a' provided more than once")
                                  symbol)))))))

            (for-each assert-unique (shepherd-service-provision service))
            (fold set-insert set (shepherd-service-provision service)))
          (setq 'shepherd)
          services))

  (define (assert-satisfied-requirements service)
    ;; Bail out if the requirements of SERVICE aren't satisfied.
    (for-each (lambda (requirement)
                (unless (set-contains? provisions requirement)
                  (raise (condition
                          (&message
                           (message
                            (format #f (_ "service '~a' requires '~a', \
which is undefined")
                                    (match (shepherd-service-provision service)
                                      ((head . _) head)
                                      (_          service))
                                    requirement)))))))
              (shepherd-service-requirement service)))

  (for-each assert-satisfied-requirements services))

(define (shepherd-service-file-name service)
  "Return the file name where the initialization code for SERVICE is to be
stored."
  (let ((provisions (string-join (map symbol->string
                                      (shepherd-service-provision service)))))
    (string-append "shepherd-"
                   (string-map (match-lambda
                                 (#\/ #\-)
                                 (chr chr))
                               provisions)
                   ".scm")))

(define (shepherd-service-file service)
  "Return a file defining SERVICE."
  (gexp->file (shepherd-service-file-name service)
              #~(begin
                  (use-modules #$@(shepherd-service-modules service))

                  (make <service>
                    #:docstring '#$(shepherd-service-documentation service)
                    #:provides '#$(shepherd-service-provision service)
                    #:requires '#$(shepherd-service-requirement service)
                    #:respawn? '#$(shepherd-service-respawn? service)
                    #:start #$(shepherd-service-start service)
                    #:stop #$(shepherd-service-stop service)))))

(define (shepherd-configuration-file services)
  "Return the shepherd configuration file for SERVICES."
  (define modules
    (delete-duplicates
     (append-map shepherd-service-imported-modules services)))

  (assert-valid-graph services)

  (mlet %store-monad ((modules  (imported-modules modules))
                      (compiled (compiled-modules modules))
                      (files    (mapm %store-monad
                                      shepherd-service-file
                                      services)))
    (define config
      #~(begin
          (eval-when (expand load eval)
            (set! %load-path (cons #$modules %load-path))
            (set! %load-compiled-path
              (cons #$compiled %load-compiled-path)))

          (use-modules (system repl error-handling))

          ;; Arrange to spawn a REPL if loading one of FILES fails.  This is
          ;; better than a kernel panic.
          (call-with-error-handling
            (lambda ()
              (apply register-services (map primitive-load '#$files))))

          ;; guix-daemon 0.6 aborts if 'PATH' is undefined, so work around it.
          (setenv "PATH" "/run/current-system/profile/bin")

          (format #t "starting services...~%")
          (for-each start
                    '#$(append-map shepherd-service-provision
                                   (filter shepherd-service-auto-start?
                                           services)))))

    (gexp->file "shepherd.conf" config)))

(define (shepherd-service-back-edges services)
  "Return a procedure that, when given a <shepherd-service> from SERVICES,
returns the list of <shepherd-service> that depend on it."
  (define provision->service
    (let ((services (fold (lambda (service result)
                            (fold (cut vhash-consq <> service <>)
                                  result
                                  (shepherd-service-provision service)))
                          vlist-null
                          services)))
      (lambda (name)
        (match (vhash-assq name services)
          ((_ . service) service)
          (#f            #f)))))

  (define edges
    (fold (lambda (service edges)
            (fold (lambda (requirement edges)
                    (vhash-consq (provision->service requirement) service
                                 edges))
                  edges
                  (shepherd-service-requirement service)))
          vlist-null
          services))

  (lambda (service)
    (vhash-foldq* cons '() service edges)))

;;; shepherd.scm ends here