aboutsummaryrefslogtreecommitdiff
path: root/gnu/services/herd.scm
blob: 48594015fcbaa465c8046638c7e0954f39d31f3d (plain)
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
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2016-2019, 2022-2023 Ludovic Courtès <ludo@gnu.org>
;;; Copyright © 2017, 2020 Mathieu Othacehe <m.othacehe@gmail.com>
;;;
;;; 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 (srfi srfi-1)
  #:use-module (srfi srfi-9)
  #:use-module (srfi srfi-9 gnu)
  #:use-module (srfi srfi-11)
  #:use-module (srfi srfi-34)
  #:use-module (srfi srfi-35)
  #:use-module (ice-9 match)
  #:export (%shepherd-socket-file
            shepherd-message-port

            shepherd-error?
            service-not-found-error?
            service-not-found-error-service
            action-not-found-error?
            action-not-found-error-service
            action-not-found-error-action
            action-exception-error?
            action-exception-error-service
            action-exception-error-action
            action-exception-error-key
            action-exception-error-arguments
            unknown-shepherd-error?
            unknown-shepherd-error-sexp

            live-service
            live-service?
            live-service-provision
            live-service-requirement
            live-service-running
            live-service-transient?
            live-service-canonical-name

            with-shepherd-action
            current-services
            unload-services
            unload-service
            load-services
            load-services/safe
            start-service
            stop-service
            restart-service
            wait-for-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
  (make-parameter "/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 'block 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)))
    (dynamic-wind
      (const #t)
      (lambda ()
        body ...)
      (lambda ()
        (close-port connection)))))

(define-condition-type &shepherd-error &error
  shepherd-error?)

(define-condition-type &service-not-found-error &shepherd-error
  service-not-found-error?
  (service service-not-found-error-service))

(define-condition-type &action-not-found-error &shepherd-error
  action-not-found-error?
  (service action-not-found-error-service)
  (action  action-not-found-error-action))

(define-condition-type &action-exception-error &shepherd-error
  action-exception-error?
  (service action-exception-error-service)
  (action  action-exception-error-action)
  (key     action-exception-error-key)
  (args    action-exception-error-arguments))

(define-condition-type &unknown-shepherd-error &shepherd-error
  unknown-shepherd-error?
  (sexp   unknown-shepherd-error-sexp))

(define (raise-shepherd-error error)
  "Raise an error condition corresponding to ERROR, an sexp received by a
shepherd client in reply to COMMAND, a command object.  Return #t if ERROR
does not denote an error."
  (match error
    (('error ('version 0 x ...) 'service-not-found service)
     (raise (condition (&service-not-found-error
                        (service service)))))
    (('error ('version 0 x ...) 'action-not-found action service)
     (raise (condition (&action-not-found-error
                        (service service)
                        (action action)))))
    (('error ('version 0 x ...) 'action-exception action service
             key (args ...))
     (raise (condition (&action-exception-error
                        (service service)
                        (action action)
                        (key key) (args args)))))
    (('error . _)
     (raise (condition (&unknown-shepherd-error (sexp error)))))
    (#f                                           ;not an error
     #t)))

(define shepherd-message-port
  ;; Port where messages coming from shepherd are printed.
  (make-parameter (current-error-port)))

(define (display-message message)
  (format (shepherd-message-port) "shepherd: ~a~%" message))

(define* (invoke-action service action arguments cont)
  "Invoke ACTION on SERVICE with ARGUMENTS.  On success, call CONT with the
list of results (one result per instance with the name SERVICE).  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)
       (raise-shepherd-error error)
       #f)
      (x
       ;; invalid reply
       #f))))

(define-syntax-rule (with-shepherd-action service (action args ...)
                      result body ...)
  "Invoke ACTION on SERVICE with the given ARGS, and evaluate BODY with RESULT
bound to the action's result."
  (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 ...))))

;; Information about live Shepherd services.
(define-record-type <live-service>
  (live-service provision requirement transient? running)
  live-service?
  (provision    live-service-provision)           ;list of symbols
  (requirement  live-service-requirement)         ;list of symbols
  (transient?   live-service-transient?)          ;Boolean
  (running      live-service-running))            ;#f | object

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

(define (current-services)
  "Return the list of currently defined Shepherd services, represented as
<live-service> objects.  Return #f if the list of services could not be
obtained."
  (with-shepherd-action 'root ('status) results
    ;; We get a list of results, one for each service with the name 'root'.
    ;; In practice there's only one such service though.
    (match results
      ((services _ ...)
       (match services
         ((('service ('version 0 _ ...) _ ...) ...)
          (resolve-transients
           (map (lambda (service)
                  (alist-let* service (provides requires running transient?)
                    ;; The Shepherd 0.9.0 would not provide 'transient?' in its
                    ;; status sexp.  Thus, when it's missing, query it via an
                    ;; "eval" request.
                    (live-service provides requires
                                  (if (sloppy-assq 'transient? service)
                                      transient?
                                      (and running *unspecified*))
                                  running)))
                services)))
         (x
          #f))))))

(define (resolve-transients services)
  "Resolve the subset of SERVICES whose 'transient?' field is undefined.  This
is necessary to deal with Shepherd 0.9.0, which did not communicate whether a
service is transient."
  ;; All the fuss here is to make sure we make a single "eval root" request
  ;; for all of SERVICES.
  (let* ((unresolved (filter (compose unspecified? live-service-transient?)
                             services))
         (values     (or (eval-there
                          `(and (defined? 'transient?) ;shepherd >= 0.9.0
                                (map (compose transient? lookup-running)
                                     ',(map (compose first
                                                     live-service-provision)
                                            unresolved))))
                         (make-list (length unresolved) #f)))
         (resolved   (map (lambda (unresolved transient?)
                            (cons unresolved
                                  (set-field unresolved
                                             (live-service-transient?)
                                             transient?)))
                          unresolved values)))
    (map (lambda (service)
           (or (assq-ref resolved service) service))
         services)))

(define (unload-service service)
  "Unload SERVICE, a symbol name; return #t on success."
  (with-shepherd-action 'root ('unload (symbol->string service)) result
    (first result)))

(define (%load-file file)
  "Load FILE in the Shepherd."
  (with-shepherd-action 'root ('load file) result
    (first result)))

(define (eval-there exp)
  "Eval EXP in the Shepherd."
  (with-shepherd-action 'root ('eval (object->string exp)) result
    (first 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 load-services/safe
  ;; Deprecated.  It used to behave differently before service replacements
  ;; were a thing.
  load-services)

(define* (start-service name #:optional (arguments '()))
  (invoke-action name 'start arguments
                 (lambda (result)
                   result)))

(define (stop-service name)
  (with-shepherd-action name ('stop) result
    result))

(define (restart-service name)
  (with-shepherd-action name ('restart) result
    result))

(define* (wait-for-service name #:key (timeout 20))
  "Wait for the service providing NAME, a symbol, to be up and running, and
return its \"running value\".  Give up after TIMEOUT seconds and raise a
'&shepherd-error' exception.  Raise a '&service-not-found-error' exception
when NAME is not found."
  (define (relevant-service? service)
    (memq name (live-service-provision service)))

  (define start
    (car (gettimeofday)))

  ;; Note: As of Shepherd 0.9.1, we cannot just call the 'start' method and
  ;; wait for it: it would spawn an additional elogind process.  Thus, poll.
  (let loop ((attempts 0))
    (define services
      (current-services))

    (define now
      (car (gettimeofday)))

    (when (>= (- now start) timeout)
      (raise (condition (&shepherd-error))))      ;XXX: better exception?

    (match (find relevant-service? services)
      (#f
       (raise (condition (&service-not-found-error
                          (service name)))))
      (service
       (or (live-service-running service)
           (begin
             (sleep 1)
             (loop (+ attempts 1))))))))

;; 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