1 ;;; 8sync --- Asynchronous programming for Guile
2 ;;; Copyright (C) 2016 Christopher Allan Webber <cwebber@dustycloud.org>
4 ;;; This file is part of 8sync.
6 ;;; 8sync is free software: you can redistribute it and/or modify it
7 ;;; under the terms of the GNU Lesser General Public License as
8 ;;; published by the Free Software Foundation, either version 3 of the
9 ;;; License, or (at your option) any later version.
11 ;;; 8sync is distributed in the hope that it will be useful,
12 ;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
13 ;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 ;;; GNU Lesser General Public License for more details.
16 ;;; You should have received a copy of the GNU Lesser General Public
17 ;;; License along with 8sync. If not, see <http://www.gnu.org/licenses/>.
19 (define-module (8sync actors)
20 #:use-module (oop goops)
21 #:use-module (srfi srfi-9)
22 #:use-module (srfi srfi-9 gnu)
23 #:use-module (ice-9 control)
24 #:use-module (ice-9 format)
25 #:use-module (ice-9 match)
26 #:use-module (ice-9 pretty-print)
27 #:use-module (8sync agenda)
28 #:use-module (8sync repl)
29 #:export (;; utilities... ought to go in their own module
31 big-random-number-string
32 simple-message-id-generator
40 ;;; Commenting out the <address> type for now;
41 ;;; it may be back when we have better serializers
44 address-actor-id address-hive-id
57 ;; There are more methods for the hive, but there's
58 ;; no reason for the outside world to look at them maybe?
60 hive-create-actor hive-create-actor*
62 create-actor create-actor*
67 message-to message-action message-from
68 message-id message-body message-in-reply-to
73 <- <-wait <-wait* <-reply <-reply-wait <-reply-wait*
75 call-with-message msg-receive msg-val
80 serialize-message write-message
81 serialize-message-pretty pprint-message
82 read-message read-message-from-string))
86 (make-parameter (random-state-from-platform)))
88 ;; Same size as a uuid4 I think...
89 (define random-number-size (expt 2 128))
91 (define (big-random-number)
92 (random random-number-size (%random-state)))
94 ;; Would be great to get this base64 encoded instead.
95 (define (big-random-number-string)
96 ;; @@: This is slow. Using format here is wasteful.
97 (format #f "~x" (big-random-number)))
99 ;; @@: This is slow. A mere ~275k / second on my (old) machine.
100 ;; The main cost seems to be in number->string.
101 (define (simple-message-id-generator)
102 ;; Prepending this cookie makes message ids unique per hive
103 (let ((prefix (format #f "~x:" (big-random-number)))
106 (set! counter (1+ counter))
107 (string-append prefix (number->string counter)))))
115 ;; @@: We may want to add a deferred-reply to the below, similar to
116 ;; what we had in XUDD, for actors which do their own response
117 ;; queueing.... ie, that might receive messages but need to shelve
118 ;; them to be acted upon after something else is taken care of.
120 (define-record-type <message>
121 (make-message-intern id to from action
122 body in-reply-to wants-reply
125 (id message-id) ; id of this message
126 (to message-to) ; actor id this is going to
127 (from message-from) ; actor id of sender
128 (action message-action) ; action (a symbol) to be handled
129 (body message-body) ; argument list "body" of message
130 (in-reply-to message-in-reply-to) ; message id this is in reply to, if any
131 (wants-reply message-wants-reply) ; whether caller is waiting for reply
132 (replied message-replied ; was this message replied to?
133 set-message-replied!))
136 (define* (make-message id to from action body
137 #:key in-reply-to wants-reply
139 (make-message-intern id to from action body
140 in-reply-to wants-reply replied))
142 (define (message-auto-reply? message)
143 (eq? (message-action message) '*auto-reply*))
145 (define (message-needs-reply? message)
146 "See if this message needs a reply still"
147 (and (message-wants-reply message)
148 (not (message-replied message))))
151 (define (kwarg-list-to-alist args)
152 (let loop ((remaining args)
155 (((? keyword? key) val rest ...)
157 (cons (cons (keyword->symbol key) val)
160 (_ (throw 'invalid-kwarg-list
161 "Invalid keyword argument list"
165 ;;; See: https://web.archive.org/web/20081223021934/http://mumble.net/~jar/articles/oo-moon-weinreb.html
166 ;;; (also worth seeing: http://mumble.net/~jar/articles/oo.html )
168 ;; This is the internal, generalized message sending method.
169 ;; Users shouldn't use it! Use the <-foo forms instead.
171 ;; @@: Could we get rid of some of the conditional checks through
174 (define-inlinable (send-message send-options from-actor to-id action
175 replying-to-message wants-reply?
177 (if replying-to-message
178 (set-message-replied! replying-to-message #t))
179 (let* ((hive (actor-hive from-actor))
181 (make-message (hive-gen-message-id hive) to-id
182 (actor-id from-actor) action
184 #:wants-reply wants-reply?
186 (if replying-to-message
187 (message-id replying-to-message)
190 (abort-to-prompt (hive-prompt (actor-hive from-actor))
191 from-actor new-message send-options)
192 ;; @@: It might be that eventually we pass in send-options
193 ;; here too. Since <-wait and <-reply-wait are the only ones
194 ;; that use it yet, for now it kind of just makes things
196 (8sync (hive-process-message hive new-message)))))
199 (define (<- from-actor to-id action . message-body-args)
200 "Send a message from an actor to another actor"
201 (send-message '() from-actor to-id action
202 #f #f message-body-args))
204 (define (<-wait* send-options from-actor to-id action . message-body-args)
205 "Like <-wait, but allows extra parameters, for example whether to
207 (apply wait-maybe-handle-errors
208 (send-message send-options from-actor to-id action
209 #f #t message-body-args)
212 (define (<-wait from-actor to-id action . message-body-args)
213 "Send a message from an actor to another, but wait until we get a response"
214 (apply <-wait* '() from-actor to-id action message-body-args))
216 ;; TODO: Intelligently ~propagate(ish) errors on -wait functions.
217 ;; We might have `send-message-wait-brazen' to allow callers to
218 ;; not have an exception thrown and instead just have a message with
219 ;; the appropriate '*error* message returned.
221 (define (<-reply from-actor original-message . message-body-args)
223 (send-message '() from-actor (message-from original-message) '*reply*
224 original-message #f message-body-args))
226 (define (<-auto-reply from-actor original-message)
227 "Auto-reply to a message. Internal use only!"
228 (send-message '() from-actor (message-from original-message) '*auto-reply*
229 original-message #f '()))
231 (define (<-reply-wait* send-options from-actor original-message
233 "Reply to a messsage, but wait until we get a response"
234 (apply wait-maybe-handle-errors
235 (send-message send-options from-actor
236 (message-from original-message) '*reply*
237 original-message #t message-body-args)
240 (define (<-reply-wait from-actor original-message . message-body-args)
241 "Reply to a messsage, but wait until we get a response"
242 (apply <-reply-wait* '() from-actor original-message message-body-args))
244 (define* (wait-maybe-handle-errors message
247 "Before returning a message to a waiting caller, see if we need to
248 raise an exception if an error."
249 (define action (message-action message))
250 (cond ((and (eq? action '*error*)
252 (throw 'hive-unresumable-coroutine
253 "Won't resume coroutine; got an *error* as a reply"
259 ;;; Main actor implementation
260 ;;; =========================
262 (define (actor-inheritable-message-handler actor message)
263 (define action (message-action message))
264 (define (find-message-handler return)
265 (for-each (lambda (this-class)
267 (or (and (class-slot-definition this-class 'actions)
268 (class-slot-ref this-class 'actions))
270 (for-each (match-lambda
271 ((action-name . method)
272 (when (eq? action-name action)
275 (class-precedence-list (class-of actor)))
276 (throw 'action-not-found
277 "No appropriate action handler found for actor"
282 (call/ec find-message-handler))
283 (apply method actor message (message-body message)))
285 (define-class <actor> ()
287 (id #:init-keyword #:id
289 ;; The hive we're connected to.
290 ;; We need this to be able to send messages.
291 (hive #:init-keyword #:hive
292 #:accessor actor-hive)
293 ;; How we receive and process new messages
294 (message-handler #:init-value actor-inheritable-message-handler
295 ;; @@: There's no reason not to use #:class instead of
296 ;; #:each-subclass anywhere in this file, except for
297 ;; Guile bug #25211 (#:class is broken in Guile 2.2)
298 #:allocation #:each-subclass)
300 ;; This is the default, "simple" way to inherit and process messages.
301 (actions #:init-value '()
302 #:allocation #:each-subclass))
304 (define-method (actor-message-handler (actor <actor>))
305 (slot-ref actor 'message-handler))
307 ;;; So these are the nicer representations of addresses.
308 ;;; However, they don't serialize so easily with scheme read/write, so we're
309 ;;; using the simpler cons cell version below for now.
311 ;; (define-record-type <address>
312 ;; (make-address actor-id hive-id) ; @@: Do we want the trailing -id?
314 ;; (actor-id address-actor-id)
315 ;; (hive-id address-hive-id))
317 ;; (set-record-type-printer!
319 ;; (lambda (record port)
320 ;; (format port "<address: ~s@~s>"
321 ;; (address-actor-id record) (address-hive-id record))))
324 (define (make-address actor-id hive-id)
325 (cons actor-id hive-id))
327 (define (address-actor-id address)
330 (define (address-hive-id address)
333 (define (address->string address)
334 (string-append (address-actor-id address) "@"
335 (address-hive-id address)))
337 (define-method (actor-id-actor (actor <actor>))
338 "Get the actor id component of the actor-id"
339 (address-actor-id (actor-id actor)))
341 (define-method (actor-id-hive (actor <actor>))
342 "Get the hive id component of the actor-id"
343 (address-hive-id (actor-id actor)))
345 (define-method (actor-id-string (actor <actor>))
346 "Render the full actor id as a human-readable string"
347 (address->string (actor-id actor)))
349 (define %current-actor
357 (define-syntax-rule (build-actions (symbol method) ...)
358 "Construct an alist of (symbol . method), where the method is wrapped
359 with wrap-apply to facilitate live hacking and allow the method definition
360 to come after class definition."
363 (wrap-apply method)) ...))
365 (define-syntax-rule (define-simple-actor class action ...)
366 (define-class class (<actor>)
367 (actions #:init-value (build-actions action ...)
368 #:allocation #:each-subclass)))
373 ;;; Every actor has a hive. The hive is a kind of "meta-actor"
374 ;;; which routes all the rest of the actors in a system.
376 (define-generic hive-handle-failed-forward)
378 (define-class <hive> (<actor>)
379 (actor-registry #:init-thunk make-hash-table
380 #:getter hive-actor-registry)
381 (msg-id-generator #:init-thunk simple-message-id-generator
382 #:getter hive-msg-id-generator)
383 ;; Ambassadors are used (or will be) for inter-hive communication.
384 ;; These are special actors that know how to route messages to other hives.
385 (ambassadors #:init-thunk make-weak-key-hash-table
386 #:getter hive-ambassadors)
387 ;; Waiting coroutines
388 ;; This is a map from cons cell of message-id
389 ;; to a cons cell of (actor-id . coroutine)
390 ;; @@: Should we have a <waiting-coroutine> record type?
391 ;; @@: Should there be any way to clear out "old" coroutines?
392 (waiting-coroutines #:init-thunk make-hash-table
393 #:getter hive-waiting-coroutines)
395 ;; When actors send messages to each other they abort to this prompt
396 ;; to send the message, then carry on their way
397 (prompt #:init-thunk make-prompt-tag
398 #:getter hive-prompt)
399 (actions #:allocation #:each-subclass
402 ;; This is in the case of an ambassador failing to forward a
403 ;; message... it reports it back to the hive
404 (*failed-forward* hive-handle-failed-forward))))
406 (define-method (hive-handle-failed-forward (hive <hive>) message)
407 "Handle an ambassador failing to forward a message"
410 (define* (make-hive #:key hive-id)
411 (let ((hive (make <hive>
414 (big-random-number-string))))))
415 ;; Set the hive's actor reference to itself
416 (set! (actor-hive hive) hive)
419 (define-method (hive-id (hive <hive>))
420 (actor-id-hive hive))
422 (define-method (hive-gen-actor-id (hive <hive>) cookie)
423 (make-address (if cookie
424 (string-append cookie "-" (big-random-number-string))
425 (big-random-number-string))
428 (define-method (hive-gen-message-id (hive <hive>))
429 "Generate a message id using HIVE's message id generator"
430 ((hive-msg-id-generator hive)))
432 (define-method (hive-resolve-local-actor (hive <hive>) actor-address)
433 (hash-ref (hive-actor-registry hive) actor-address))
435 (define-method (hive-resolve-ambassador (hive <hive>) ambassador-address)
436 (hash-ref (hive-ambassadors hive) ambassador-address))
438 (define-method (make-forward-request (hive <hive>) (ambassador <actor>) message)
439 (make-message (hive-gen-message-id hive) (actor-id ambassador)
440 ;; If we make the hive not an actor, we could either switch this
441 ;; to #f or to the original actor...?
442 ;; Maybe some more thinking should be done on what should
443 ;; happen in case of failure to forward? Handling ambassador failures
444 ;; seems like the primary motivation for the hive remaining an actor.
447 `((original . ,message))))
449 (define-method (hive-reply-with-error (hive <hive>) original-message
450 error-key error-args)
451 ;; We only supply the error-args if the original sender is on the same hive
452 (define (orig-actor-on-same-hive?)
453 (equal? (hive-id hive)
454 (address-hive-id (message-from original-message))))
455 (set-message-replied! original-message #t)
456 (let* ((new-message-body
457 (if (orig-actor-on-same-hive?)
458 `(#:original-message ,original-message
459 #:error-key ,error-key
460 #:error-args ,error-args)
461 `(#:original-message ,original-message
462 #:error-key ,error-key)))
463 (new-message (make-message (hive-gen-message-id hive)
464 (message-from original-message)
465 (actor-id hive) '*error*
467 #:in-reply-to (message-id original-message))))
468 ;; We only return a thunk, rather than run 8sync here, because if
469 ;; we ran 8sync in the middle of a catch we'd end up with an
470 ;; unresumable continuation.
471 (lambda () (hive-process-message hive new-message))))
473 (define-record-type <waiting-on-reply>
474 (make-waiting-on-reply actor-id kont send-options)
476 (actor-id waiting-on-reply-actor-id)
477 (kont waiting-on-reply-kont)
478 (send-options waiting-on-reply-send-options))
481 (define-method (hive-process-message (hive <hive>) message)
482 "Handle one message, or forward it via an ambassador"
483 (define (maybe-autoreply actor)
484 ;; Possibly autoreply
485 (if (message-needs-reply? message)
486 (<-auto-reply actor message)))
488 (define (resolve-actor-to)
489 "Get the actor the message was aimed at"
490 (let ((actor (hive-resolve-local-actor hive (message-to message))))
492 (throw 'actor-not-found
493 (format #f "Message ~a from ~a directed to nonexistant actor ~a"
495 (address->string (message-from message))
496 (address->string (message-to message)))
500 (define (call-catching-coroutine thunk)
501 (define queued-error-handling-thunk #f)
502 (define (call-catching-errors)
503 ;; TODO: maybe parameterize (or attach to hive) and use
504 ;; maybe-catch-all from agenda.scm
505 ;; @@: Why not just use with-throw-handler and let the catch
506 ;; happen at the agenda? That's what we used to do, but
507 ;; it ended up with a SIGABRT. See:
508 ;; http://lists.gnu.org/archive/html/bug-guile/2016-05/msg00003.html
511 ;; In the actor model, we don't totally crash on errors.
513 ;; If an error happens, we raise it
515 (if (message-needs-reply? message)
516 ;; If the message is waiting on a reply, let them know
517 ;; something went wrong.
518 ;; However, we have to do it outside of this catch
519 ;; routine, or we'll end up in an unrewindable continuation
521 (set! queued-error-handling-thunk
522 (hive-reply-with-error hive message key args)))
523 ;; print error message
524 (apply print-error-and-continue key args)))
525 ;; @@: This is a kludge. See above for why.
526 (if queued-error-handling-thunk
527 (8sync (queued-error-handling-thunk))))
528 (call-with-prompt (hive-prompt hive)
530 (lambda (kont actor message send-options)
531 ;; Register the coroutine
532 (hash-set! (hive-waiting-coroutines hive)
534 (make-waiting-on-reply
535 (actor-id actor) kont send-options))
536 ;; Send off the message
537 (8sync (hive-process-message hive message)))))
539 (define (process-local-message)
540 (let ((actor (resolve-actor-to)))
541 (call-catching-coroutine
543 (define message-handler (actor-message-handler actor))
544 ;; @@: Should a more general error handling happen here?
545 (parameterize ((%current-actor actor))
547 (message-handler actor message)))
548 (maybe-autoreply actor)
549 ;; Returning result allows actors to possibly make a run-request
550 ;; at the end of handling a message.
551 ;; ... We do want that, right?
554 (define (resume-waiting-coroutine)
555 (case (message-action message)
556 ;; standard reply / auto-reply
557 ((*reply* *auto-reply* *error*)
558 (call-catching-coroutine
560 (match (hash-remove! (hive-waiting-coroutines hive)
561 (message-in-reply-to message))
563 (if (not (equal? (message-to message)
564 (waiting-on-reply-actor-id waiting)))
565 (throw 'resuming-to-wrong-actor
566 "Attempted to resume a coroutine to the wrong actor!"
567 #:expected-actor-id (message-to message)
568 #:got-actor-id (waiting-on-reply-actor-id waiting)
570 (let* (;; @@: How should we resolve resuming coroutines to actors who are
572 (actor (resolve-actor-to))
573 (kont (waiting-on-reply-kont waiting))
574 (result (kont message)))
575 (maybe-autoreply actor)
577 (#f (throw 'no-waiting-coroutine
578 "message in-reply-to tries to resume nonexistent coroutine"
580 ;; Unhandled action for a reply!
582 (throw 'hive-unresumable-coroutine
583 "Won't resume coroutine, nonsense action on reply message"
584 #:action (message-action message)
585 #:message message))))
587 (define (process-remote-message)
588 ;; Find the ambassador
589 (let* ((remote-hive-id (hive-id (message-to message)))
590 (ambassador (hive-resolve-ambassador remote-hive-id))
591 (message-handler (actor-message-handler ambassador))
592 (forward-request (make-forward-request hive ambassador message)))
593 (message-handler ambassador forward-request)))
595 (let ((to (message-to message)))
596 ;; This seems to be an easy mistake to make, so check that addressing
599 (throw 'missing-addressee
600 "`to' field is missing on message"
602 (if (hive-actor-local? hive to)
603 (if (message-in-reply-to message)
604 (resume-waiting-coroutine)
605 (process-local-message))
606 (process-remote-message))))
608 (define-method (hive-actor-local? (hive <hive>) address)
609 (equal? (hive-id hive) (address-hive-id address)))
611 (define-method (hive-register-actor! (hive <hive>) (actor <actor>))
612 (hash-set! (hive-actor-registry hive) (actor-id actor) actor))
614 (define-method (%hive-create-actor (hive <hive>) actor-class
616 "Actual method called by hive-create-actor.
618 Since this is a define-method it can't accept fancy define* arguments,
619 so this gets called from the nicer hive-create-actor interface. See
620 that method for documentation."
621 (let* ((actor-id (hive-gen-actor-id hive id-cookie))
622 (actor (apply make actor-class
626 (hive-register-actor! hive actor)
627 ;; return the actor id
630 (define* (hive-create-actor hive actor-class #:rest init)
631 (%hive-create-actor hive actor-class
634 (define* (hive-create-actor* hive actor-class id-cookie #:rest init)
635 "Create an actor, but also add a 'cookie' to the name for debugging"
636 (%hive-create-actor hive actor-class
639 (define (call-with-message message proc)
640 "Applies message body arguments into procedure, with message as first
641 argument. Similar to call-with-values in concept."
642 (apply proc message (message-body message)))
644 ;; (msg-receive (<- bar baz)
648 ;; Emacs: (put 'msg-receive 'scheme-indent-function 2)
650 ;; @@: Or receive-msg or receieve-message or??
651 (define-syntax-rule (msg-receive arglist message body ...)
652 "Call body with arglist (which can accept arguments like lambda*)
653 applied from the message-body of message."
654 (call-with-message message
658 (define (msg-val message)
659 "Retrieve the first value from the message-body of message.
660 Like single value return from a procedure call. Probably the most
661 common case when waiting on a reply from some action invocation."
662 (call-with-message message
663 (lambda (_ val) val)))
666 ;;; Various API methods for actors to interact with the system
667 ;;; ==========================================================
669 ;; TODO: move send-message and friends here...?
671 (define* (create-actor from-actor actor-class #:rest init)
672 "Create an instance of actor-class. Return the new actor's id.
674 This is the method actors should call directly (unless they want
675 to supply an id-cookie, in which case they should use
677 (%hive-create-actor (actor-hive from-actor) actor-class
681 (define* (create-actor* from-actor actor-class id-cookie #:rest init)
682 "Create an instance of actor-class. Return the new actor's id.
684 Like create-actor, but permits supplying an id-cookie."
685 (%hive-create-actor (actor-hive from-actor) actor-class
689 (define (self-destruct actor)
690 "Remove an actor from the hive."
691 (hash-remove! (hive-actor-registry (actor-hive actor))
696 ;;; 8sync bootstrap utilities
697 ;;; =========================
699 (define* (ez-run-hive hive initial-tasks #:key repl-server)
700 "Start up an agenda and run HIVE in it with INITIAL-TASKS.
702 Should we start up a cooperative REPL for live hacking? REPL-SERVER
703 wants to know! You can pass it #t or #f, or if you want to specify a port,
705 (let* ((queue (list->q initial-tasks))
706 (agenda (make-agenda #:pre-unwind-handler print-error-and-continue
709 ;; If repl-server is an integer, we'll use that as the port
710 ((integer? repl-server)
711 (spawn-and-queue-repl-server! agenda repl-server))
713 (spawn-and-queue-repl-server! agenda)))
714 (start-agenda agenda)))
716 (define (bootstrap-message hive to-id action . message-body-args)
718 (apply <- hive to-id action message-body-args)))
722 ;;; Basic readers / writers
723 ;;; =======================
725 (define (serialize-message message)
726 "Serialize a message for read/write"
730 (message-from message)
731 (message-action message)
732 (message-body message)
733 (message-in-reply-to message)
734 (message-wants-reply message)
735 (message-replied message)))
737 (define* (write-message message #:optional (port (current-output-port)))
738 "Write out a message to a port for easy reading later.
740 Note that if a sub-value can't be easily written to something
741 Guile's `read' procedure knows how to read, this doesn't do anything
742 to improve that. You'll need a better serializer for that.."
743 (write (serialize-message message) port))
745 (define (serialize-message-pretty message)
746 "Serialize a message in a way that's easy for humans to read."
748 (id ,(message-id message))
749 (to ,(message-to message))
750 (from ,(message-from message))
751 (action ,(message-action message))
752 (body ,(message-body message))
753 (in-reply-to ,(message-in-reply-to message))
754 (wants-reply ,(message-wants-reply message))
755 (replied ,(message-replied message))))
757 (define (pprint-message message)
758 "Pretty print a message."
759 (pretty-print (serialize-message-pretty message)))
761 (define* (read-message #:optional (port (current-input-port)))
762 "Read a message serialized via serialize-message from PORT"
764 ((id to from action body in-reply-to wants-reply replied)
766 id to from action body
767 in-reply-to wants-reply replied))
769 (throw 'message-read-bad-structure
770 "Could not read message from structure"
773 (define (read-message-from-string message-str)
774 "Read message from MESSAGE-STR"
775 (with-input-from-string message-str
777 (read-message (current-input-port)))))