128 lines
5.6 KiB
Racket
128 lines
5.6 KiB
Racket
#lang racket/base
|
|
;; A structure (and process!) for matching supply to demand via observation of interests.
|
|
|
|
(require racket/set)
|
|
(require racket/match)
|
|
(require "core.rkt")
|
|
(require "drivers/timer.rkt")
|
|
(require "../prospect/pretty.rkt")
|
|
|
|
(provide (except-out (struct-out demand-matcher) demand-matcher)
|
|
(rename-out [make-demand-matcher demand-matcher])
|
|
demand-matcher-update
|
|
spawn-demand-matcher)
|
|
|
|
;; A DemandMatcher keeps track of demand for services based on some
|
|
;; Projection over a Trie, as well as a collection of functions
|
|
;; that can be used to increase supply in response to increased
|
|
;; demand, or handle a sudden drop in supply for which demand still
|
|
;; exists.
|
|
(struct demand-matcher (demand-spec ;; CompiledProjection
|
|
supply-spec ;; CompiledProjection
|
|
increase-handler ;; ChangeHandler
|
|
decrease-handler ;; ChangeHandler
|
|
current-demand ;; (Setof (Listof Any))
|
|
current-supply) ;; (Setof (Listof Any))
|
|
#:transparent
|
|
#:methods gen:prospect-pretty-printable
|
|
[(define (prospect-pretty-print s [p (current-output-port)])
|
|
(pretty-print-demand-matcher s p))])
|
|
|
|
;; A ChangeHandler is a ((Constreeof Action) Any* -> (Constreeof Action)).
|
|
;; It is called with an accumulator of actions so-far-computed as its
|
|
;; first argument, and with a value for each capture in the
|
|
;; DemandMatcher's projection as the remaining arguments.
|
|
|
|
;; ChangeHandler
|
|
;; Default handler of unexpected supply decrease.
|
|
(define (default-decrease-handler state . removed-captures)
|
|
state)
|
|
|
|
(define (make-demand-matcher demand-spec supply-spec increase-handler decrease-handler)
|
|
(demand-matcher demand-spec
|
|
supply-spec
|
|
increase-handler
|
|
decrease-handler
|
|
(set)
|
|
(set)))
|
|
|
|
;; DemandMatcher (Constreeof Action) SCN -> (Transition DemandMatcher)
|
|
;; Given a SCN from the environment, projects it into supply and
|
|
;; demand increase and decrease sets. Calls ChangeHandlers in response
|
|
;; to increased unsatisfied demand and decreased demanded supply.
|
|
(define (demand-matcher-update d s new-scn)
|
|
(match-define (demand-matcher demand-spec supply-spec inc-h dec-h demand supply) d)
|
|
(define new-demand (trie-project/set (scn-trie new-scn) demand-spec))
|
|
(define new-supply (trie-project/set (scn-trie new-scn) supply-spec))
|
|
(define added-demand (set-subtract new-demand demand))
|
|
(define removed-demand (set-subtract demand new-demand))
|
|
(define added-supply (set-subtract new-supply supply))
|
|
(define removed-supply (set-subtract supply new-supply))
|
|
|
|
(when (not added-demand) (error 'demand-matcher "Wildcard demand of ~v:\n~a"
|
|
demand-spec
|
|
(trie->pretty-string (scn-trie new-scn))))
|
|
(when (not added-supply) (error 'demand-matcher "Wildcard supply of ~v:\n~a"
|
|
supply-spec
|
|
(trie->pretty-string (scn-trie new-scn))))
|
|
|
|
(set! supply (set-union supply added-supply))
|
|
(set! demand (set-subtract demand removed-demand))
|
|
|
|
(for [(captures (in-set removed-supply))]
|
|
(when (set-member? demand captures) (set! s (apply dec-h s captures))))
|
|
(for [(captures (in-set added-demand))]
|
|
(when (not (set-member? supply captures)) (set! s (apply inc-h s captures))))
|
|
|
|
(set! supply (set-subtract supply removed-supply))
|
|
(set! demand (set-union demand added-demand))
|
|
|
|
(transition (struct-copy demand-matcher d [current-demand demand] [current-supply supply]) s))
|
|
|
|
;; Behavior :> (Option Event) DemandMatcher -> (Transition DemandMatcher)
|
|
;; Handles events from the environment. Only cares about routing-updates.
|
|
(define (demand-matcher-handle-event e d)
|
|
(match e
|
|
[(? scn? s)
|
|
(demand-matcher-update d '() s)]
|
|
[_ #f]))
|
|
|
|
;; Any* -> (Constreeof Action)
|
|
;; Default handler of unexpected supply decrease.
|
|
;; Ignores the situation.
|
|
(define (unexpected-supply-decrease . removed-captures)
|
|
'())
|
|
|
|
;; Projection Projection (Any* -> (Constreeof Action)) [(Any* -> (Constreeof Action))] -> Action
|
|
;; Spawns a demand matcher actor.
|
|
(define (spawn-demand-matcher demand-spec
|
|
supply-spec
|
|
increase-handler
|
|
[decrease-handler unexpected-supply-decrease]
|
|
#:meta-level [meta-level 0])
|
|
(define d (make-demand-matcher (compile-projection (prepend-at-meta demand-spec meta-level))
|
|
(compile-projection (prepend-at-meta supply-spec meta-level))
|
|
(lambda (acs . rs) (cons (apply increase-handler rs) acs))
|
|
(lambda (acs . rs) (cons (apply decrease-handler rs) acs))))
|
|
(spawn demand-matcher-handle-event
|
|
d
|
|
(scn/union (subscription (projection->pattern demand-spec) #:meta-level meta-level)
|
|
(subscription (projection->pattern supply-spec) #:meta-level meta-level)
|
|
(advertisement (projection->pattern supply-spec) #:meta-level meta-level))))
|
|
|
|
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
|
|
|
(define (pretty-print-demand-matcher s [p (current-output-port)])
|
|
(match-define (demand-matcher demand-spec
|
|
supply-spec
|
|
increase-handler
|
|
decrease-handler
|
|
current-demand
|
|
current-supply)
|
|
s)
|
|
(fprintf p "DEMAND MATCHER:\n")
|
|
(fprintf p " - demand-spec: ~v\n" demand-spec)
|
|
(fprintf p " - supply-spec: ~v\n" supply-spec)
|
|
(fprintf p " - demand: ~v\n" current-demand)
|
|
(fprintf p " - supply: ~v\n" current-supply))
|