;; Simple Actor Machine
;;
-;; Houses a population of actors which can communicate using messages
-;; with actors on the same machine or other machines via the network.
+;; A virtual machine which houses a population of actors which can
+;; communicate using messages with actors on the same host or other
+;; hosts via the network.
-(import (chicken io)
+(import scheme
+ (chicken base)
+ (chicken io)
(chicken string)
+ (chicken port)
+ (chicken process-context)
+ (chicken file)
+ (chicken condition)
matchable
srfi-18 ; threads
srfi-69 ; hash-table
+ uuid ; ids for actors
+ uri-generic
udp
- fifo)
+ fifo
+ sam-macros)
-;; Actors
+;; Global variables
+
+(define trace #f)
+
+(define sam-host "localhost")
+(define sam-port 8000)
+
+(define sam-version "0.1")
+
+;; Logging
+
+(define (log-msg . args)
+ (with-output-to-port (current-error-port)
+ (lambda ()
+ (apply print (cons "## " args)))))
+
+(define (log-trace . args)
+ (with-output-to-port (current-error-port)
+ (lambda ()
+ (if trace (apply log-msg args)))))
+
+(define (->stringrep arg)
+ (with-output-to-string
+ (lambda ()
+ (write arg))))
-(define (make-machine host port)
- (cons host port))
-(define (machine-host m) (car m))
-(define (machine-port m) (cdr m))
+;; Behaviours
+;; (See also macros defined in sam-macros.scm.)
-(define this-machine (make-machine "localhost" 1234))
+(define (beh-proc beh)
+ (cadr beh))
+(define (beh-parent beh)
+ (caddr beh))
-(define next-actor-id 1)
+(define root-beh
+ (make-beh : #f (self)
+ (('ping recipient) =>
+ (send-message recipient 'pong))))
-(define (address-id address) (car address))
-(define (address-machine address) (cdr address))
-(define (make-address id machine)
- (cons id machine))
+(define (beh? x)
+ (and (pair? x)
+ (not (null? x))
+ (eq? (car x) 'beh)))
+
+;; Actors
+
+(define (make-address host port id)
+ (list id host port))
+
+(define (make-local-address . args)
+ (make-address sam-host
+ sam-port
+ (if (null? args)
+ (uuid)
+ (car args))))
+
+(define (address-id address)
+ (car address))
+(define (address-host address)
+ (cadr address))
+(define (address-port address)
+ (caddr address))
+(define (address->string address)
+ (uri->string
+ (make-uri #:scheme "actor"
+ #:host (address-host address)
+ #:port (address-port address)
+ #:path (list '/ (address-id address)))))
+(define (string->address str)
+ (let ((uri (uri-reference str)))
+ (make-address (uri-host uri)
+ (uri-port uri)
+ (cadr (uri-path uri)))))
(define (address-local? address)
- (equal? (address-machine address)
- this-machine))
+ (and (equal? (address-host address) sam-host)
+ (equal? (address-port address) sam-port)))
(define actor-table (make-hash-table))
(define (make-actor beh)
- (let* ((id next-actor-id))
+ (let* ((address (make-local-address))
+ (id (address-id address)))
(hash-table-set! actor-table id beh)
- (make-address id this-machine)))
-
+ address))
+
(define (deliver-message address . message)
(let ((id (address-id address)))
- (let ((behaviour (hash-table-ref/default actor-table id '())))
- (if (null? behaviour)
- (print "Warning: discarded message" message " to unknown actor " address)
- (match (apply (hash-table-ref actor-table id) (cons address message))
- ('done (hash-table-delete! actor-table actor))
- ('sleep 'do-nothing)
- (new-beh (hash-table-set! actor-table actor new-beh)))))))
+ (log-trace "DELIVERING to " id ": " (->stringrep message))
+ (let loop ((beh (hash-table-ref/default actor-table id #f)))
+ (if beh
+ (condition-case
+ (match (apply (beh-proc beh) (cons address message))
+ ('done (hash-table-delete! actor-table id))
+ ('pass
+ (log-trace "Passing to parent behaviour...")
+ (loop (beh-parent beh)))
+ ((? beh? new-beh) (hash-table-set! actor-table id new-beh))
+ (else
+ 'do-nothing)) ; sleep is now the default
+ (o (exn)
+ (log-msg "Warning: actor " id " crashed evaluating message " (->stringrep message))
+ (print-error-message o)))
+ (log-msg "Warning: DISCARDING message to unknown actor " id ": " (->stringrep message))))))
;; Scheduler
(define local-queue (make-fifo))
(define (send-message address . message)
+ (log-trace "SENDING to " address ": " (->stringrep message))
(apply (if (address-local? address)
send-local-message
send-network-message)
- message))
+ (cons address message)))
(define (send-local-message address . message)
(mutex-lock! local-queue-mutex)
(define (send-network-message address . message)
(let ((s (udp-open-socket))
- (machine (address-machine address)))
+ (packet (with-output-to-string
+ (lambda ()
+ (write (cons address message))))))
(udp-bind! s #f 0)
(udp-connect! s
- (machine-host machine)
- (machine-port machine))
- (udp-send s message)
+ (address-host address)
+ (address-port address))
+ (udp-send s packet)
(udp-close-socket s)))
+(define (send-message-later address time . message)
+ (thread-start!
+ (lambda ()
+ (thread-sleep! time)
+ (apply send-message (cons address message)))))
+
(define (next-local-message)
(let ((res #f))
(mutex-lock! message-available-mutex #f #f)
(mutex-lock! local-queue-mutex)
(set! res (fifo-pop local-queue))
(if (not (fifo-empty? local-queue))
- (mutex-unlock! message-available-mutex))
+ (mutex-unlock! message-available-mutex))
(mutex-unlock! local-queue-mutex)
res))
-(define scheduler-thread
- (make-thread
+(define (start-scheduler)
+ (let loop ()
+ (apply deliver-message (next-local-message))
+ (loop)))
+
+
+;; Network
+
+(define (start-network-listener)
+ (thread-start!
+ (lambda ()
+ (let ((s (udp-open-socket*)))
+ (udp-bind! s #f sam-port)
+ (let loop ()
+ (let-values (((n str) (udp-recv s 65536)))
+ (match (with-input-from-string str read)
+ ((address message ...)
+ (apply send-message (cons address message)))
+ (else
+ (log-msg "Warning: received badly formatted message string '" str "'"))))
+ (loop))))))
+
+;; System interface
+
+(define reader-queue-mutex (make-mutex "reader queue"))
+(define reader-available-mutex (make-mutex "reader available"))
+(mutex-lock! reader-available-mutex #f #f)
+(define reader-queue (make-fifo))
+
+(define (next-reader)
+ (let ((res #f))
+ (mutex-lock! reader-available-mutex #f #f)
+ (mutex-lock! reader-queue-mutex)
+ (set! res (fifo-pop reader-queue))
+ (if (not (fifo-empty? reader-queue))
+ (mutex-unlock! reader-available-mutex))
+ (mutex-unlock! reader-queue-mutex)
+ res))
+
+(define (start-console)
+ (thread-start!
(lambda ()
- (let loop ((next-addressed-message (next-local-message)))
- (apply deliver-message next-addressed-message)
- (loop (next-local-message))))))
+ (let loop ()
+ (let ((reader (next-reader)))
+ (##sys#thread-block-for-i/o! (current-thread) 0 #t)
+ (thread-yield!)
+ (send-message reader (read-line)))
+ (loop)))))
+
+;; System initialization
+
+(define-beh system-beh
+ (self)
+
+ (('shutdown) =>
+ (log-msg "System actor received shutdown message.")
+ (exit 0)
+ 'done)
+ (('print strings ...) =>
+ (apply print strings))
-;; Testing
+ (('read reader) =>
+ (mutex-lock! reader-queue-mutex)
+ (fifo-push reader-queue reader)
+ (mutex-unlock! reader-available-mutex)
+ (mutex-unlock! reader-queue-mutex)))
-(thread-start! scheduler-thread)
+(define (boot-sam)
+ (start-console)
+ (start-network-listener)
+ (let ((system (make-actor system-beh))
+ (main #f))
+ (condition-case
+ (begin
+ (set! main (make-actor main-beh)))
+ ((exn)
+ (log-msg "Error starting main actor. Is main-beh defined?")
+ (exit 1)))
+ (send-message main system))
+ (start-scheduler))
-(define println
- (make-actor (lambda (self . message)
- (apply print message)
- 'sleep)))
+(define (print-usage)
+ (print "Simple Actor Machine v" sam-version "\n"
+ "\n"
+ "Usage: sam -h|--help\n"
+ " sam [-n hostname] [-p port] source-file-1 [source-file-2 [...]] "))
-(print println)
-(send-message println "Hello, world!")
+(let loop ((args (cdr (argv))))
+ (match args
+ (((or "-h" "--help"))
+ (print-usage))
+ (((or "-p" "--port") pstr rest ...)
+ (set! sam-port (string->number pstr))
+ (loop rest))
+ (((or "-n" "--hostname") hstr rest ...)
+ (set! sam-host hstr)
+ (loop rest))
+ (((or "-t" "--trace") rest ...)
+ (log-msg "Enabling trace debugging")
+ (set! trace #t)
+ (loop rest))
+ (((? file-exists? filename) rest ...)
+ (log-msg "Loading " filename)
+ (load filename)
+ (loop rest))
+ (()
+ (log-msg "Booting SAM\n")
+ (boot-sam))
+ (else
+ (print "Unrecognised argument '" (car args) "'.\n")
+ (print-usage))))
-(thread-join! scheduler-thread)
The Lambda Lab / projects / sam.git / blobdiff