+++ /dev/null
-;;; 8sync --- Asynchronous programming for Guile
-;;; Copyright (C) 2016 Christopher Allan Webber <cwebber@dustycloud.org>
-;;;
-;;; This file is part of 8sync.
-;;;
-;;; 8sync is free software: you can redistribute it and/or modify it
-;;; under the terms of the GNU Lesser General Public License as
-;;; published by the Free Software Foundation, either version 3 of the
-;;; License, or (at your option) any later version.
-;;;
-;;; 8sync 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 Lesser General Public License for more details.
-;;;
-;;; You should have received a copy of the GNU Lesser General Public
-;;; License along with 8sync. If not, see <http://www.gnu.org/licenses/>.
-
-;; XUDD inspired actor system
-
-(define-module (8sync systems actors)
- #:use-module (oop goops)
- #:use-module (srfi srfi-9)
- #:use-module (srfi srfi-9 gnu)
- #:use-module (ice-9 control)
- #:use-module (ice-9 format)
- #:use-module (ice-9 match)
- #:use-module (ice-9 pretty-print)
- #:use-module (8sync agenda)
- #:use-module (8sync repl)
- #:export (;; utilities... ought to go in their own module
- big-random-number
- big-random-number-string
- simple-message-id-generator
-
- <actor>
- actor-id
- actor-message-handler
-
- %current-actor
-
- ;;; Commenting out the <address> type for now;
- ;;; it may be back when we have better serializers
- ;; <address>
- make-address address?
- address-actor-id address-hive-id
-
- address->string
- actor-id-actor
- actor-id-hive
- actor-id-string
-
- build-actions
-
- define-simple-actor
-
- <hive>
- make-hive
- ;; There are more methods for the hive, but there's
- ;; no reason for the outside world to look at them maybe?
- hive-id
- hive-create-actor hive-create-actor*
-
- create-actor create-actor*
- self-destruct
-
- <message>
- make-message message?
- message-to message-action message-from
- message-id message-body message-in-reply-to
- message-wants-reply
-
- message-auto-reply?
-
- <- <-wait <-reply <-reply-wait
-
- call-with-message msg-receive msg-val
-
- ez-run-hive
- bootstrap-message
-
- serialize-message write-message
- serialize-message-pretty pprint-message
- read-message read-message-from-string))
-
-;; For ids
-(define %random-state
- (make-parameter (random-state-from-platform)))
-
-;; Same size as a uuid4 I think...
-(define random-number-size (expt 2 128))
-
-(define (big-random-number)
- (random random-number-size (%random-state)))
-
-;; Would be great to get this base64 encoded instead.
-(define (big-random-number-string)
- ;; @@: This is slow. Using format here is wasteful.
- (format #f "~x" (big-random-number)))
-
-;; @@: This is slow. A mere ~275k / second on my (old) machine.
-;; The main cost seems to be in number->string.
-(define (simple-message-id-generator)
- ;; Prepending this cookie makes message ids unique per hive
- (let ((prefix (format #f "~x:" (big-random-number)))
- (counter 0))
- (lambda ()
- (set! counter (1+ counter))
- (string-append prefix (number->string counter)))))
-
-
-\f
-;;; Messages
-;;; ========
-
-
-;; @@: We may want to add a deferred-reply to the below, similar to
-;; what we had in XUDD, for actors which do their own response
-;; queueing.... ie, that might receive messages but need to shelve
-;; them to be acted upon after something else is taken care of.
-
-(define-record-type <message>
- (make-message-intern id to from action
- body in-reply-to wants-reply
- replied)
- message?
- (id message-id)
- (to message-to)
- (from message-from)
- (action message-action)
- (body message-body)
- (in-reply-to message-in-reply-to)
- (wants-reply message-wants-reply)
- (replied message-replied set-message-replied!))
-
-
-(define* (make-message id to from action body
- #:key in-reply-to wants-reply
- replied)
- (make-message-intern id to from action body
- in-reply-to wants-reply replied))
-
-(define (message-auto-reply? message)
- (eq? (message-action message) '*auto-reply*))
-
-(define (message-needs-reply? message)
- "See if this message needs a reply still"
- (and (message-wants-reply message)
- (not (message-replied message))))
-
-
-(define (kwarg-list-to-alist args)
- (let loop ((remaining args)
- (result '()))
- (match remaining
- (((? keyword? key) val rest ...)
- (loop rest
- (cons (cons (keyword->symbol key) val)
- result)))
- (() result)
- (_ (throw 'invalid-kwarg-list
- "Invalid keyword argument list"
- args)))))
-
-
-;;; See: https://web.archive.org/web/20081223021934/http://mumble.net/~jar/articles/oo-moon-weinreb.html
-;;; (also worth seeing: http://mumble.net/~jar/articles/oo.html )
-
-(define (<- from-actor to-id action . message-body-args)
- "Send a message from an actor to another actor"
- (let* ((hive (actor-hive from-actor))
- (message (make-message (hive-gen-message-id hive) to-id
- (actor-id from-actor) action
- message-body-args)))
- (8sync (hive-process-message hive message))))
-
-(define (<-wait from-actor to-id action . message-body-args)
- "Send a message from an actor to another, but wait until we get a response"
- (let* ((hive (actor-hive from-actor))
- (abort-to (hive-prompt (actor-hive from-actor)))
- (message (make-message (hive-gen-message-id hive) to-id
- (actor-id from-actor) action
- message-body-args
- #:wants-reply #t)))
- (abort-to-prompt abort-to from-actor message)))
-
-;; TODO: Intelligently ~propagate(ish) errors on -wait functions.
-;; We might have `send-message-wait-brazen' to allow callers to
-;; not have an exception thrown and instead just have a message with
-;; the appropriate '*error* message returned.
-
-(define (<-reply from-actor original-message . message-body-args)
- "Reply to a message"
- (set-message-replied! original-message #t)
- (let* ((hive (actor-hive from-actor))
- (new-message (make-message (hive-gen-message-id hive)
- (message-from original-message)
- (actor-id from-actor) '*reply*
- message-body-args
- #:in-reply-to (message-id original-message))))
- (8sync (hive-process-message hive new-message))))
-
-(define (<-auto-reply from-actor original-message)
- "Auto-reply to a message. Internal use only!"
- (set-message-replied! original-message #t)
- (let* ((hive (actor-hive from-actor))
- (new-message (make-message (hive-gen-message-id hive)
- (message-from original-message)
- (actor-id from-actor) '*auto-reply*
- '()
- #:in-reply-to (message-id original-message))))
- (8sync (hive-process-message hive new-message))))
-
-(define (<-reply-wait from-actor original-message . message-body-args)
- "Reply to a messsage, but wait until we get a response"
- (set-message-replied! original-message #t)
- (let* ((hive (actor-hive from-actor))
- (abort-to (hive-prompt (actor-hive from-actor)))
- (new-message (make-message (hive-gen-message-id hive)
- (message-from original-message)
- (actor-id from-actor) '*reply*
- message-body-args
- #:wants-reply #t
- #:in-reply-to (message-id original-message))))
- (abort-to-prompt abort-to from-actor new-message)))
-
-
-\f
-;;; Main actor implementation
-;;; =========================
-
-(define (actor-inheritable-message-handler actor message)
- (define action (message-action message))
- (define (find-message-handler return)
- (for-each (lambda (this-class)
- (define actions
- (or (and (class-slot-definition this-class 'actions)
- (class-slot-ref this-class 'actions))
- '()))
- (for-each (match-lambda
- ((action-name . method)
- (when (eq? action-name action)
- (return method))))
- actions))
- (class-precedence-list (class-of actor)))
- (throw 'action-not-found
- "No appropriate action handler found for actor"
- #:action action
- #:actor actor
- #:message message))
- (define method
- (call/ec find-message-handler))
- (apply method actor message (message-body message)))
-
-(define-class <actor> ()
- ;; An address object
- (id #:init-keyword #:id
- #:getter actor-id)
- ;; The hive we're connected to.
- ;; We need this to be able to send messages.
- (hive #:init-keyword #:hive
- #:accessor actor-hive)
- ;; How we receive and process new messages
- (message-handler #:init-value actor-inheritable-message-handler
- ;; @@: There's no reason not to use #:class instead of
- ;; #:each-subclass anywhere in this file, except for
- ;; Guile bug #25211 (#:class is broken in Guile 2.2)
- #:allocation #:each-subclass)
-
- ;; This is the default, "simple" way to inherit and process messages.
- (actions #:init-value '()
- #:allocation #:each-subclass))
-
-(define-method (actor-message-handler (actor <actor>))
- (slot-ref actor 'message-handler))
-
-;;; So these are the nicer representations of addresses.
-;;; However, they don't serialize so easily with scheme read/write, so we're
-;;; using the simpler cons cell version below for now.
-
-;; (define-record-type <address>
-;; (make-address actor-id hive-id) ; @@: Do we want the trailing -id?
-;; address?
-;; (actor-id address-actor-id)
-;; (hive-id address-hive-id))
-;;
-;; (set-record-type-printer!
-;; <address>
-;; (lambda (record port)
-;; (format port "<address: ~s@~s>"
-;; (address-actor-id record) (address-hive-id record))))
-;;
-
-(define (make-address actor-id hive-id)
- (cons actor-id hive-id))
-
-(define (address-actor-id address)
- (car address))
-
-(define (address-hive-id address)
- (cdr address))
-
-(define (address->string address)
- (string-append (address-actor-id address) "@"
- (address-hive-id address)))
-
-(define-method (actor-id-actor (actor <actor>))
- "Get the actor id component of the actor-id"
- (address-actor-id (actor-id actor)))
-
-(define-method (actor-id-hive (actor <actor>))
- "Get the hive id component of the actor-id"
- (address-hive-id (actor-id actor)))
-
-(define-method (actor-id-string (actor <actor>))
- "Render the full actor id as a human-readable string"
- (address->string (actor-id actor)))
-
-(define %current-actor
- (make-parameter #f))
-
-
-\f
-;;; Actor utilities
-;;; ===============
-
-(define-syntax-rule (build-actions (symbol method) ...)
- "Construct an alist of (symbol . method), where the method is wrapped
-with wrap-apply to facilitate live hacking and allow the method definition
-to come after class definition."
- (list
- (cons (quote symbol)
- (wrap-apply method)) ...))
-
-(define-syntax-rule (define-simple-actor class action ...)
- (define-class class (<actor>)
- (actions #:init-value (build-actions action ...)
- #:allocation #:each-subclass)))
-
-\f
-;;; The Hive
-;;; ========
-;;; Every actor has a hive. The hive is a kind of "meta-actor"
-;;; which routes all the rest of the actors in a system.
-
-(define-generic hive-handle-failed-forward)
-
-(define-class <hive> (<actor>)
- (actor-registry #:init-thunk make-hash-table
- #:getter hive-actor-registry)
- (msg-id-generator #:init-thunk simple-message-id-generator
- #:getter hive-msg-id-generator)
- ;; Ambassadors are used (or will be) for inter-hive communication.
- ;; These are special actors that know how to route messages to other hives.
- (ambassadors #:init-thunk make-weak-key-hash-table
- #:getter hive-ambassadors)
- ;; Waiting coroutines
- ;; This is a map from cons cell of message-id
- ;; to a cons cell of (actor-id . coroutine)
- ;; @@: Should we have a <waiting-coroutine> record type?
- ;; @@: Should there be any way to clear out "old" coroutines?
- (waiting-coroutines #:init-thunk make-hash-table
- #:getter hive-waiting-coroutines)
- ;; Message prompt
- ;; When actors send messages to each other they abort to this prompt
- ;; to send the message, then carry on their way
- (prompt #:init-thunk make-prompt-tag
- #:getter hive-prompt)
- (actions #:allocation #:each-subclass
- #:init-value
- (build-actions
- ;; This is in the case of an ambassador failing to forward a
- ;; message... it reports it back to the hive
- (*failed-forward* hive-handle-failed-forward))))
-
-(define-method (hive-handle-failed-forward (hive <hive>) message)
- "Handle an ambassador failing to forward a message"
- 'TODO)
-
-(define* (make-hive #:key hive-id)
- (let ((hive (make <hive>
- #:id (make-address
- "hive" (or hive-id
- (big-random-number-string))))))
- ;; Set the hive's actor reference to itself
- (set! (actor-hive hive) hive)
- hive))
-
-(define-method (hive-id (hive <hive>))
- (actor-id-hive hive))
-
-(define-method (hive-gen-actor-id (hive <hive>) cookie)
- (make-address (if cookie
- (string-append cookie "-" (big-random-number-string))
- (big-random-number-string))
- (hive-id hive)))
-
-(define-method (hive-gen-message-id (hive <hive>))
- "Generate a message id using HIVE's message id generator"
- ((hive-msg-id-generator hive)))
-
-(define-method (hive-resolve-local-actor (hive <hive>) actor-address)
- (hash-ref (hive-actor-registry hive) actor-address))
-
-(define-method (hive-resolve-ambassador (hive <hive>) ambassador-address)
- (hash-ref (hive-ambassadors hive) ambassador-address))
-
-(define-method (make-forward-request (hive <hive>) (ambassador <actor>) message)
- (make-message (hive-gen-message-id hive) (actor-id ambassador)
- ;; If we make the hive not an actor, we could either switch this
- ;; to #f or to the original actor...?
- ;; Maybe some more thinking should be done on what should
- ;; happen in case of failure to forward? Handling ambassador failures
- ;; seems like the primary motivation for the hive remaining an actor.
- (actor-id hive)
- '*forward*
- `((original . ,message))))
-
-(define-method (hive-reply-with-error (hive <hive>) original-message
- error-key error-args)
- ;; We only supply the error-args if the original sender is on the same hive
- (define (orig-actor-on-same-hive?)
- (equal? (hive-id hive)
- (address-hive-id (message-from original-message))))
- (set-message-replied! original-message #t)
- (let* ((new-message-body
- (if (orig-actor-on-same-hive?)
- `(#:original-message ,original-message
- #:error-key ,error-key
- #:error-args ,error-args)
- `(#:original-message ,original-message
- #:error-key ,error-key)))
- (new-message (make-message (hive-gen-message-id hive)
- (message-from original-message)
- (actor-id hive) '*error*
- new-message-body
- #:in-reply-to (message-id original-message))))
- ;; We only return a thunk, rather than run 8sync here, because if
- ;; we ran 8sync in the middle of a catch we'd end up with an
- ;; unresumable continuation.
- (lambda () (hive-process-message hive new-message))))
-
-(define-method (hive-process-message (hive <hive>) message)
- "Handle one message, or forward it via an ambassador"
- (define (maybe-autoreply actor)
- ;; Possibly autoreply
- (if (message-needs-reply? message)
- (<-auto-reply actor message)))
-
- (define (resolve-actor-to)
- "Get the actor the message was aimed at"
- (let ((actor (hive-resolve-local-actor hive (message-to message))))
- (if (not actor)
- (throw 'actor-not-found
- (format #f "Message ~a from ~a directed to nonexistant actor ~a"
- (message-id message)
- (address->string (message-from message))
- (address->string (message-to message)))
- message))
- actor))
-
- (define (call-catching-coroutine thunk)
- (define queued-error-handling-thunk #f)
- (define (call-catching-errors)
- ;; TODO: maybe parameterize (or attach to hive) and use
- ;; maybe-catch-all from agenda.scm
- ;; @@: Why not just use with-throw-handler and let the catch
- ;; happen at the agenda? That's what we used to do, but
- ;; it ended up with a SIGABRT. See:
- ;; http://lists.gnu.org/archive/html/bug-guile/2016-05/msg00003.html
- (catch #t
- thunk
- ;; In the actor model, we don't totally crash on errors.
- (lambda _ #f)
- ;; If an error happens, we raise it
- (lambda (key . args)
- (if (message-needs-reply? message)
- ;; If the message is waiting on a reply, let them know
- ;; something went wrong.
- ;; However, we have to do it outside of this catch
- ;; routine, or we'll end up in an unrewindable continuation
- ;; situation.
- (set! queued-error-handling-thunk
- (hive-reply-with-error hive message key args)))
- ;; print error message
- (apply print-error-and-continue key args)))
- ;; @@: This is a kludge. See above for why.
- (if queued-error-handling-thunk
- (8sync (queued-error-handling-thunk))))
- (call-with-prompt (hive-prompt hive)
- call-catching-errors
- (lambda (kont actor message)
- ;; Register the coroutine
- (hash-set! (hive-waiting-coroutines hive)
- (message-id message)
- (cons (actor-id actor) kont))
- ;; Send off the message
- (8sync (hive-process-message hive message)))))
-
- (define (process-local-message)
- (let ((actor (resolve-actor-to)))
- (call-catching-coroutine
- (lambda ()
- (define message-handler (actor-message-handler actor))
- ;; @@: Should a more general error handling happen here?
- (parameterize ((%current-actor actor))
- (let ((result
- (message-handler actor message)))
- (maybe-autoreply actor)
- ;; Returning result allows actors to possibly make a run-request
- ;; at the end of handling a message.
- ;; ... We do want that, right?
- result))))))
-
- (define (resume-waiting-coroutine)
- (cond
- ((or (eq? (message-action message) '*reply*)
- (eq? (message-action message) '*auto-reply*))
- (call-catching-coroutine
- (lambda ()
- (match (hash-remove! (hive-waiting-coroutines hive)
- (message-in-reply-to message))
- ((_ . (resume-actor-id . kont))
- (if (not (equal? (message-to message)
- resume-actor-id))
- (throw 'resuming-to-wrong-actor
- "Attempted to resume a coroutine to the wrong actor!"
- #:expected-actor-id (message-to message)
- #:got-actor-id resume-actor-id
- #:message message))
- (let (;; @@: How should we resolve resuming coroutines to actors who are
- ;; now gone?
- (actor (resolve-actor-to))
- (result (kont message)))
- (maybe-autoreply actor)
- result))
- (#f (throw 'no-waiting-coroutine
- "message in-reply-to tries to resume nonexistent coroutine"
- message))))))
- ;; Yikes, we must have gotten an error or something back
- (else
- ;; @@: Not what we want in the long run?
- ;; What we'd *prefer* to do is to resume this message
- ;; and throw an error inside the message handler
- ;; (say, from send-mesage-wait), but that causes a SIGABRT (??!!)
- (hash-remove! (hive-waiting-coroutines hive)
- (message-in-reply-to message))
- (let ((explaination
- (if (eq? (message-action message) '*reply*)
- "Won't resume coroutine; got an *error* as a reply"
- "Won't resume coroutine because action is not *reply*")))
- (throw 'hive-unresumable-coroutine
- explaination
- #:message message)))))
-
- (define (process-remote-message)
- ;; Find the ambassador
- (let* ((remote-hive-id (hive-id (message-to message)))
- (ambassador (hive-resolve-ambassador remote-hive-id))
- (message-handler (actor-message-handler ambassador))
- (forward-request (make-forward-request hive ambassador message)))
- (message-handler ambassador forward-request)))
-
- (let ((to (message-to message)))
- ;; This seems to be an easy mistake to make, so check that addressing
- ;; is correct here
- (if (not to)
- (throw 'missing-addressee
- "`to' field is missing on message"
- #:message message))
- (if (hive-actor-local? hive to)
- (if (message-in-reply-to message)
- (resume-waiting-coroutine)
- (process-local-message))
- (process-remote-message))))
-
-(define-method (hive-actor-local? (hive <hive>) address)
- (equal? (hive-id hive) (address-hive-id address)))
-
-(define-method (hive-register-actor! (hive <hive>) (actor <actor>))
- (hash-set! (hive-actor-registry hive) (actor-id actor) actor))
-
-(define-method (%hive-create-actor (hive <hive>) actor-class
- init id-cookie)
- "Actual method called by hive-create-actor.
-
-Since this is a define-method it can't accept fancy define* arguments,
-so this gets called from the nicer hive-create-actor interface. See
-that method for documentation."
- (let* ((actor-id (hive-gen-actor-id hive id-cookie))
- (actor (apply make actor-class
- #:hive hive
- #:id actor-id
- init)))
- (hive-register-actor! hive actor)
- ;; return the actor id
- actor-id))
-
-(define* (hive-create-actor hive actor-class #:rest init)
- (%hive-create-actor hive actor-class
- init #f))
-
-(define* (hive-create-actor* hive actor-class id-cookie #:rest init)
- (%hive-create-actor hive actor-class
- init id-cookie))
-
-(define (call-with-message message proc)
- "Applies message body arguments into procedure, with message as first
-argument. Similar to call-with-values in concept."
- (apply proc message (message-body message)))
-
-;; (msg-receive (<- bar baz)
-;; (baz)
-;; basil)
-
-;; Emacs: (put 'msg-receive 'scheme-indent-function 2)
-
-;; @@: Or receive-msg or receieve-message or??
-(define-syntax-rule (msg-receive arglist message body ...)
- "Call body with arglist (which can accept arguments like lambda*)
-applied from the message-body of message."
- (call-with-message message
- (lambda* arglist
- body ...)))
-
-(define (msg-val message)
- "Retrieve the first value from the message-body of message.
-Like single value return from a procedure call. Probably the most
-common case when waiting on a reply from some action invocation."
- (call-with-message message
- (lambda (_ val) val)))
-
-\f
-;;; Various API methods for actors to interact with the system
-;;; ==========================================================
-
-;; TODO: move send-message and friends here...?
-
-(define* (create-actor from-actor actor-class #:rest init)
- "Create an instance of actor-class. Return the new actor's id.
-
-This is the method actors should call directly (unless they want
-to supply an id-cookie, in which case they should use
-create-actor*)."
- (%hive-create-actor (actor-hive from-actor) actor-class
- init #f))
-
-
-(define* (create-actor* from-actor actor-class id-cookie #:rest init)
- "Create an instance of actor-class. Return the new actor's id.
-
-Like create-actor, but permits supplying an id-cookie."
- (%hive-create-actor (actor-hive from-actor) actor-class
- init id-cookie))
-
-
-(define (self-destruct actor)
- "Remove an actor from the hive."
- (hash-remove! (hive-actor-registry (actor-hive actor))
- (actor-id actor)))
-
-
-\f
-;;; 8sync bootstrap utilities
-;;; =========================
-
-(define* (ez-run-hive hive initial-tasks #:key repl-server)
- "Start up an agenda and run HIVE in it with INITIAL-TASKS.
-
-Should we start up a cooperative REPL for live hacking? REPL-SERVER
-wants to know! You can pass it #t or #f, or if you want to specify a port,
-an integer."
- (let* ((queue (list->q initial-tasks))
- (agenda (make-agenda #:pre-unwind-handler print-error-and-continue
- #:queue queue)))
- (cond
- ;; If repl-server is an integer, we'll use that as the port
- ((integer? repl-server)
- (spawn-and-queue-repl-server! agenda repl-server))
- (repl-server
- (spawn-and-queue-repl-server! agenda)))
- (start-agenda agenda)))
-
-(define (bootstrap-message hive to-id action . message-body-args)
- (wrap
- (apply <- hive to-id action message-body-args)))
-
-
-\f
-;;; Basic readers / writers
-;;; =======================
-
-(define (serialize-message message)
- "Serialize a message for read/write"
- (list
- (message-id message)
- (message-to message)
- (message-from message)
- (message-action message)
- (message-body message)
- (message-in-reply-to message)
- (message-wants-reply message)
- (message-replied message)))
-
-(define* (write-message message #:optional (port (current-output-port)))
- "Write out a message to a port for easy reading later.
-
-Note that if a sub-value can't be easily written to something
-Guile's `read' procedure knows how to read, this doesn't do anything
-to improve that. You'll need a better serializer for that.."
- (write (serialize-message message) port))
-
-(define (serialize-message-pretty message)
- "Serialize a message in a way that's easy for humans to read."
- `(*message*
- (id ,(message-id message))
- (to ,(message-to message))
- (from ,(message-from message))
- (action ,(message-action message))
- (body ,(message-body message))
- (in-reply-to ,(message-in-reply-to message))
- (wants-reply ,(message-wants-reply message))
- (replied ,(message-replied message))))
-
-(define (pprint-message message)
- "Pretty print a message."
- (pretty-print (serialize-message-pretty message)))
-
-(define* (read-message #:optional (port (current-input-port)))
- "Read a message serialized via serialize-message from PORT"
- (match (read port)
- ((id to from action body in-reply-to wants-reply replied)
- (make-message-intern
- id to from action body
- in-reply-to wants-reply replied))
- (anything-else
- (throw 'message-read-bad-structure
- "Could not read message from structure"
- anything-else))))
-
-(define (read-message-from-string message-str)
- "Read message from MESSAGE-STR"
- (with-input-from-string message-str
- (lambda ()
- (read-message (current-input-port)))))
projects / 8sync.git / blobdiff