134 lines
4.5 KiB
Racket
134 lines
4.5 KiB
Racket
#lang minimart
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;; Generic broker for WebSockets-based minimart/marketplace communication.
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(require net/rfc6455)
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(require minimart/drivers/timer)
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(require minimart/drivers/websocket)
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(require minimart/demand-matcher)
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(require minimart/pattern)
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(require json)
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;; Main: start WebSocket server
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(log-events-and-actions? #f)
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(define ping-interval (* 1000 (max (- (ws-idle-timeout) 10) (* (ws-idle-timeout) 0.8))))
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(spawn-timer-driver)
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(spawn-websocket-driver)
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(define (spawn-server-listener port ssl-options)
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(define server-id (websocket-server port ssl-options))
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(spawn-demand-matcher (websocket-message (websocket-remote-client ?) server-id ?)
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#:meta-level 1
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#:demand-is-subscription? #f
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(match-lambda ;; arrived-demand-route, i.e. new connection publisher
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[(route _ (websocket-message c _ _) 1 _)
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(spawn-connection-handler c server-id)]
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[_ '()])))
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(spawn-world
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(spawn-server-listener 8000 #f)
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(spawn-server-listener 8443 (websocket-ssl-options "server-cert.pem" "private-key.pem")))
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;; Wire protocol representation of events and actions
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(define (drop-json-pattern p)
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(pattern-subst p (hasheq '__ "__") ?))
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(define (drop-json-route r)
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(match r
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[`(,pub-or-sub ,pattern ,meta-level ,level)
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(route (match pub-or-sub ["sub" #t] ["pub" #f])
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(drop-json-pattern pattern)
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meta-level
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level)]))
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(define (drop-json-action j)
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(match j
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["ping" 'ping]
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["pong" 'pong]
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[`("routes" ,routes) (routing-update (map drop-json-route routes))]
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[`("message" ,body ,meta-level ,feedback?) (message body meta-level feedback?)]))
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(define (lift-json-pattern p)
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(pattern-subst p ? (hasheq '__ "__")))
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(define (lift-json-route r)
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(match r
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[(route sub? p ml l) `(,(if sub? "sub" "pub") ,(lift-json-pattern p) ,ml ,l)]))
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(define (lift-json-event j)
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(match j
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['ping "ping"]
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['pong "pong"]
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[(routing-update rs) `("routes" ,(map lift-json-route rs))]
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[(message body meta-level feedback?) `("message" ,body ,meta-level ,feedback?)]))
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(require racket/trace)
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(trace drop-json-action)
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(trace lift-json-event)
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;; Connections
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(struct connection-state (client-id tunnelled-routes) #:transparent)
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(define (spawn-connection-handler c server-id)
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(define (send-event e s)
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(send (websocket-message server-id
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(connection-state-client-id s)
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(jsexpr->string (lift-json-event e)))
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#:meta-level 1))
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(define ((handle-connection-routing-change rs) s)
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(match rs
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['() (transition s (quit))] ;; websocket connection closed
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[_ (transition s '())]))
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(define ((handle-tunnelled-routing-change rs) s)
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(transition s (send-event (routing-update rs) s)))
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(define ((handle-tunnellable-message m) s)
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(if (ormap (lambda (r) (route-accepts? r m)) (connection-state-tunnelled-routes s))
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(transition s (send-event m s))
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(transition s '())))
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(define relay-connections
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(list (sub (timer-expired c ?) #:meta-level 1)
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(sub (websocket-message c server-id ?) #:meta-level 1)
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(sub (websocket-message c server-id ?) #:meta-level 1 #:level 1)
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(pub (websocket-message server-id c ?) #:meta-level 1)))
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(define (connection-handler e s)
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(match e
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[(routing-update rs)
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(sequence-transitions
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(transition s '())
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(handle-connection-routing-change (intersect-routes rs relay-connections))
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(handle-tunnelled-routing-change
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(intersect-routes rs (connection-state-tunnelled-routes s))))]
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[(? message? m)
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(sequence-transitions
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(match m
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[(message (websocket-message from to data) 1 #f)
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(match (drop-json-action (string->jsexpr data))
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[(routing-update rs-unfiltered)
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(define rs (filter (lambda (r) (zero? (route-meta-level r))) rs-unfiltered))
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(transition (struct-copy connection-state s [tunnelled-routes rs])
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(routing-update (append rs relay-connections)))]
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[(? message? m)
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(transition s (if (zero? (message-meta-level m)) m '()))]
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['ping
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(transition s (send-event 'pong s))]
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['pong
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(transition s '())])]
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[(message (timer-expired _ _) 1 #f)
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(transition s (list (send (set-timer c ping-interval 'relative) #:meta-level 1)
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(send-event 'ping s)))]
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[_
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(transition s '())])
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(handle-tunnellable-message m))]
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[#f #f]))
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(list (send (set-timer c ping-interval 'relative) #:meta-level 1)
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(spawn connection-handler
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(connection-state c '())
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relay-connections)))
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