syndicate-2017/prospect/core.rkt

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#lang racket/base
;; Core implementation of Incremental Network Calculus.
(provide (struct-out message)
(except-out (struct-out quit) quit)
(rename-out [quit <quit>])
(except-out (struct-out spawn) spawn)
(rename-out [spawn <spawn>])
(struct-out transition)
(struct-out world)
(all-from-out "patch.rkt")
;; imported from route.rkt:
?
wildcard?
?!
(struct-out capture)
pretty-print-matcher
matcher->pretty-string
matcher-non-empty?
matcher-empty?
matcher-empty
projection->pattern
compile-projection
matcher-project
matcher-project/set
matcher-project/set/single
event?
action?
meta-label?
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prepend-at-meta
assert
retract
sub
unsub
pub
unpub
(rename-out [make-quit quit])
make-world
spawn-world
(rename-out [spawn-process spawn])
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spawn/stateless
make-spawn-world
transition-bind
sequence-transitions
world-handle-event
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clean-transition
pretty-print-world)
(require racket/set)
(require racket/match)
(require (only-in racket/list flatten))
(require "functional-queue.rkt")
(require "route.rkt")
(require "patch.rkt")
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(require "trace.rkt")
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(require "mux.rkt")
(module+ test (require rackunit))
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;; Events = Patches Messages
(struct message (body) #:prefab)
;; Actions ⊃ Events
(struct spawn (boot) #:prefab)
;; A Behavior is a ((Option Event) Any -> Transition): a function
;; mapping an Event (or, in the #f case, a poll signal) and a
;; Process's current state to a Transition.
;;
;; A Transition is either
;; - #f, a signal from a Process that it is inert and need not be
;; scheduled until some Event relevant to it arrives; or,
;; - a (transition Any (Constreeof Action)), a new Process state to
;; be held by its World and a sequence of Actions for the World
;; to take on the transitioning Process's behalf.
;; - a (quit (Constreeof Action)), signalling that the Process should
;; never again be handed an event, and that any queued actions
;; should be performed, followed by the sequence of Actions given,
;; and then the process should be garbage-collected.
(struct transition (state actions) #:transparent)
(struct quit (actions) #:prefab)
;; A PID is a Nat.
;; A Label is a PID or 'meta.
;; VM private states
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(struct world (mux ;; Multiplexer
pending-action-queue ;; (Queueof (Cons Label (U Action 'quit)))
runnable-pids ;; (Setof PID)
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behaviors ;; (HashTable PID Behavior)
states ;; (HashTable PID Any)
) #:transparent)
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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(define (event? x) (or (patch? x) (message? x)))
(define (action? x) (or (event? x) (spawn? x)))
(define (prepend-at-meta pattern level)
(if (zero? level)
pattern
(at-meta (prepend-at-meta pattern (- level 1)))))
(define (observe-at-meta pattern level)
(if (zero? level)
(pattern->matcher #t (observe pattern))
(matcher-union
(pattern->matcher #t (observe (prepend-at-meta pattern level)))
(pattern->matcher #t (at-meta (embedded-matcher (observe-at-meta pattern (- level 1))))))))
(define (assert pattern #:meta-level [level 0])
(patch (pattern->matcher #t (prepend-at-meta pattern level)) (matcher-empty)))
(define (retract pattern #:meta-level [level 0])
(patch (matcher-empty) (pattern->matcher #t (prepend-at-meta pattern level))))
(define (sub pattern #:meta-level [level 0])
(patch (observe-at-meta pattern level) (matcher-empty)))
(define (unsub pattern #:meta-level [level 0])
(patch (matcher-empty) (observe-at-meta pattern level)))
(define (pub pattern #:meta-level [level 0]) (assert (advertise pattern) #:meta-level level))
(define (unpub pattern #:meta-level [level 0]) (retract (advertise pattern) #:meta-level level))
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
(define (ensure-transition v)
(if (or (not v) (transition? v) (quit? v))
v
(raise (exn:fail:contract (format "Expected transition, quit or #f; got ~v" v)
(current-continuation-marks)))))
(define (clean-transition t)
(match t
[#f #f]
[(quit actions) (quit (clean-actions actions))]
[(transition state actions) (transition state (clean-actions actions))]))
(define (clean-actions actions)
(filter (lambda (x) (and (action? x) (not (patch-empty? x)))) (flatten actions)))
(define (send-event e pid w)
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(define behavior (hash-ref (world-behaviors w) pid #f))
(define old-state (hash-ref (world-states w) pid #f))
(if (not behavior)
w
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(begin
(trace-process-step e pid behavior old-state)
(invoke-process pid
(lambda () (clean-transition (ensure-transition (behavior e old-state))))
(match-lambda
[#f w]
[(and q (quit final-actions))
(trace-process-step-result e pid behavior old-state #f q)
(enqueue-actions (disable-process pid #f w) pid (append final-actions
(list 'quit)))]
[(and t (transition new-state new-actions))
(trace-process-step-result e pid behavior old-state #f t)
(enqueue-actions (mark-pid-runnable (update-state w pid new-state) pid)
pid
new-actions)])
(lambda (exn)
(trace-process-step-result e pid behavior old-state exn #f)
(enqueue-actions (disable-process pid exn w) pid (list 'quit)))))))
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(define (update-state w pid s)
(struct-copy world w [states (hash-set (world-states w) pid s)]))
(define (send-event/guard delta pid w)
(if (patch-empty? delta)
w
(send-event delta pid w)))
(define (disable-process pid exn w)
(when exn
(log-error "Process ~a died with exception:\n~a"
(cons pid (trace-pid-stack))
(exn->string exn)))
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(struct-copy world w
[behaviors (hash-remove (world-behaviors w) pid)]
[states (hash-remove (world-states w) pid)]))
(define (invoke-process pid thunk k-ok k-exn)
(define-values (ok? result)
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(call-in-trace-context
pid
(lambda ()
(with-handlers ([(lambda (exn) #t) (lambda (exn) (values #f exn))])
(values #t (with-continuation-mark 'minimart-process pid (thunk)))))))
(if ok?
(k-ok result)
(k-exn result)))
(define (mark-pid-runnable w pid)
(struct-copy world w [runnable-pids (set-add (world-runnable-pids w) pid)]))
(define (enqueue-actions w label actions)
(struct-copy world w
[pending-action-queue
(queue-append-list (world-pending-action-queue w)
(for/list [(a actions)] (cons label a)))]))
(define (make-quit . actions)
(quit actions))
(define-syntax-rule (spawn-process behavior-exp initial-state-exp initial-patch-exp ...)
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(spawn (lambda ()
(list (patch-seq initial-patch-exp ...)
behavior-exp
initial-state-exp))))
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(define-syntax-rule (spawn/stateless behavior-exp initial-patch-exp ...)
(spawn-process (stateless-behavior-wrap behavior-exp)
(void)
initial-patch-exp ...))
(define ((stateless-behavior-wrap b) e state)
(match (b e)
[#f #f]
[(? quit? q) q]
[actions (transition state actions)]))
(define-syntax-rule (spawn-world boot-action ...)
(make-spawn-world (lambda () (list boot-action ...))))
(define (make-world boot-actions)
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(world (mux)
(list->queue (for/list ((a (in-list (clean-actions boot-actions)))) (cons 'meta a)))
(set)
(hash)
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(hash)))
(define (make-spawn-world boot-actions-thunk)
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(spawn (lambda ()
(list empty-patch
world-handle-event
(make-world (boot-actions-thunk))))))
(define (transition-bind k t0)
(match t0
[#f (error 'transition-bind "Cannot bind from transition #f with continuation ~v" k)]
[(quit _) t0]
[(transition state0 actions0)
(match (k state0)
[#f t0]
[(quit actions1) (quit (cons actions0 actions1))]
[(transition state1 actions1) (transition state1 (cons actions0 actions1))])]))
(define (sequence-transitions t0 . steps)
(foldl transition-bind t0 steps))
(define (inert? w)
(and (queue-empty? (world-pending-action-queue w))
(set-empty? (world-runnable-pids w))))
(define (world-handle-event e w)
(if (or e (not (inert? w)))
(sequence-transitions (transition w '())
(inject-event e)
perform-actions
(lambda (w) (or (step-children w) (transition w '()))))
(step-children w)))
(define ((inject-event e) w)
(transition (match e
[#f w]
[(? patch? delta) (enqueue-actions w 'meta (list (lift-patch delta)))]
[(message body) (enqueue-actions w 'meta (list (message (at-meta body))))])
'()))
(define (perform-actions w)
(for/fold ([wt (transition (struct-copy world w [pending-action-queue (make-queue)]) '())])
((entry (in-list (queue->list (world-pending-action-queue w)))))
(match-define [cons label a] entry)
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(trace-internal-action label a (transition-state wt))
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(define wt1 (transition-bind (perform-action label a) wt))
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(trace-internal-action-result label a (transition-state wt) wt1)
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wt1))
(define ((perform-action label a) w)
(match a
[(spawn boot)
(invoke-process 'booting
(lambda ()
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(match (boot)
[(and results (list (? patch?) (? procedure?) _))
results]
[other
(error 'spawn
"Spawn boot procedure must yield boot spec; received ~v"
other)]))
(lambda (results)
(match-define (list initial-patch behavior initial-state) results)
(define-values (new-mux new-pid patches meta-action)
(mux-add-stream (world-mux w) initial-patch))
(let* ((w (update-state w new-pid initial-state))
(w (mark-pid-runnable w new-pid))
(w (struct-copy world w
[mux new-mux]
[behaviors (hash-set (world-behaviors w)
new-pid
behavior)]))
(w (deliver-patches w patches meta-action)))
w))
(lambda (exn)
(log-error "Spawned process in world ~a died with exception:\n~a"
(trace-pid-stack)
(exn->string exn))
(transition w '())))]
['quit
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(define-values (new-mux _label patches meta-action) (mux-remove-stream (world-mux w) label))
(deliver-patches (struct-copy world w [mux new-mux])
;; ^ behavior & state already removed by disable-process
patches
meta-action)]
[(? patch? delta-orig)
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(define-values (new-mux _label patches meta-action)
(mux-update-stream (world-mux w) label delta-orig))
(deliver-patches (struct-copy world w [mux new-mux])
patches
meta-action)]
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[(and m (message body))
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(define-values (send-to-meta? affected-pids) (mux-route-message (world-mux w) label body))
(transition (for/fold [(w w)] [(pid (in-list affected-pids))]
(send-event m pid w))
(and send-to-meta? (message (at-meta-claim body))))]))
(define (deliver-patches w patches meta-action)
(transition (for/fold [(w w)] [(entry (in-list patches))]
(match-define (cons label event) entry)
(send-event/guard event label w))
meta-action))
(define (step-children w)
(define runnable-pids (world-runnable-pids w))
(if (set-empty? runnable-pids)
#f ;; world is inert.
(transition (for/fold [(w (struct-copy world w [runnable-pids (set)]))]
[(pid (in-set runnable-pids))]
(send-event #f pid w))
'())))
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(define (pretty-print-world w [p (current-output-port)])
(local-require racket/pretty)
(match-define (world mux qs runnable behaviors states) w)
(fprintf p "WORLD:\n")
(fprintf p " - ~a queued actions\n" (queue-length qs))
(fprintf p " - ~a runnable pids ~a\n" (set-count runnable) (set->list runnable))
(fprintf p " - ~a live processes (~a with claims)\n"
(hash-count states)
(hash-count (mux-interest-table mux)))
(fprintf p " - next pid: ~a\n" (mux-next-pid mux))
(fprintf p " - routing table:\n")
(pretty-print-matcher (mux-routing-table mux) p)
(for ([pid (set-union (hash-keys (mux-interest-table mux)) (hash-keys states))])
(fprintf p " ---- process ~a, behavior ~v, STATE:\n" pid (hash-ref behaviors pid #f))
(define state (hash-ref states pid #f))
(display (indented-port-output 6 (lambda (p)
(if (world? state)
(pretty-print-world state p)
(pretty-write state p))))
p)
(newline p)
(fprintf p " process ~a, behavior ~v, CLAIMS:\n" pid (hash-ref behaviors pid #f))
(display (indented-port-output 6 (lambda (p)
(pretty-print-matcher (mux-interests-of mux pid) p)))
p)
(newline p)))
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
(module+ test
(require racket/pretty)
(define (step* w)
(let loop ((w w) (actions '()))
(pretty-print w)
(match (world-handle-event #f w)
[#f (values w (flatten actions))]
[(quit new-actions) (values w (flatten (cons actions new-actions)))]
[(transition new-w new-actions) (loop new-w (cons actions new-actions))])))
(step* (make-world '()))
)