#lang syndicate/actor (require racket/dict) (require racket/set) (require file/sha1) (require/activate syndicate/drivers/timestate) (require/activate syndicate/drivers/web) (require/activate "../config.rkt") (require "../private/util.rkt") (require "../protocol.rkt") (module+ test (require rackunit)) (define (set-minimum xs) (for/fold [(i #f)] [(candidate (in-set xs))] (cond [(not candidate) i] [(not i) candidate] [(< candidate i) candidate] [else i]))) (define (shrink-lease seconds) (if (< seconds 100) (* seconds 9/10) (- seconds 10))) (module+ test (check-equal? (shrink-lease 1000) 990) (check-equal? (shrink-lease 101) 91) (check-equal? (shrink-lease 100) 90) (check-equal? (shrink-lease 90) 81) (check-equal? (shrink-lease 50) 45)) (actor #:name 'remote-topic-manager (during/actor (remote-topic-demand $full-topic) #:name (list 'remote-topic full-topic) (remote-topic-main full-topic))) (define (remote-topic-main full-topic) (define sub-id (random-hex-string 16)) (log-info "Remote sub endpoint ~a for topic ~s" sub-id full-topic) (field [current-content-hash #f] [current-content-type #f] [current-upstream-hub #f] [established-upstream-hub #f]) (field [last-upstream-check 0] [poll-interval-seconds #f] [next-subscription-refresh #f]) (define/query-config min-poll-interval 60) (define/query-config max-upstream-redirects 5) (define/query-config subscription-retry-delay 600) (define/query-set poll-intervals (topic-demand full-topic $i) i) (begin/dataflow (define candidate (set-minimum (poll-intervals))) (poll-interval-seconds (and candidate (max candidate (min-poll-interval))))) (begin/dataflow (log-info "Poll interval for ~a is now ~a" full-topic (match (poll-interval-seconds) [#f "disabled"] [n (format "~a seconds" n)]))) (during (canonical-baseurl $baseurl) (define callback (canonical-url baseurl `("sub" (,sub-id ())))) (define (refresh-subscription!) ;; TODO: shared secret (define hub (current-upstream-hub)) ;; keep a stable value, lest it change underneath us (when hub (log-info "Subscribing to hub ~s for topic ~s" hub full-topic) (analyze-response (lambda () (web-post/form-parameters! hub `((hub.callback . ,callback) (hub.mode . "subscribe") (hub.topic . ,full-topic)))) (lambda () (when (equal? (current-upstream-hub) hub) ;; it may have changed asynchronously (established-upstream-hub hub))) (lambda (resp response-body) (log-warning "Upstream subscription to hub ~s for topic ~s failed:\n - headers: ~v\n - body: ~s" hub full-topic resp response-body) (next-subscription-refresh (+ (current-inexact-milliseconds) (* 1000.0 (subscription-retry-delay)))))))) (define (unsubscribe!) (define hub (established-upstream-hub)) (when hub (log-info "Unsubscribing from hub ~s for topic ~s" hub full-topic) (analyze-response (lambda () (web-post/form-parameters! hub `((hub.callback . ,callback) (hub.mode . "unsubscribe") (hub.topic . ,full-topic)))) void (lambda (resp response-body) (log-warning "Upstream unsubscription from hub ~s for topic ~s failed:\n - headers: ~v\n - body: ~s" hub full-topic resp response-body))) (when (equal? (established-upstream-hub) hub) ;; it may have changed asynchronously (established-upstream-hub #f)))) (field [poll-busy? #f]) ;; Ensure we only run one poll at once (define (poll-upstream!) (when (not (poll-busy?)) (poll-busy? #t) (log-info "Checking upstream ~a" full-topic) (define-values (resp response-body) (web-request! 'get full-topic #:redirect-budget (max-upstream-redirects))) (last-upstream-check (current-inexact-milliseconds)) (match (web-response-header-code-type resp) ['successful (define new-content-hash (sha1 (open-input-bytes response-body))) (define new-content-type (dict-ref (web-response-header-headers resp) 'content-type #f)) (define parsed-link-headers (parse-link-headers (web-response-header-headers resp))) (define upstream-hub (link-header-ref parsed-link-headers 'hub #f)) (define upstream-topic (link-header-ref parsed-link-headers 'self #f)) (when (not (and (equal? (current-content-hash) new-content-hash) (equal? (current-content-type) new-content-type))) (current-content-hash new-content-hash) (current-content-type new-content-type) (send! (notification full-topic upstream-hub upstream-topic response-body new-content-type))) (current-upstream-hub upstream-hub)] [other (log-warning "Upstream ~a yielded ~a code ~a during poll" full-topic other (web-response-header-code resp))]) (poll-busy? #f))) (on-start (poll-upstream!)) ;; always check at least once, for discovery (on-stop (unsubscribe!)) (on-stop (log-info "Remote topic ~s terminating" full-topic)) (begin/dataflow (when (not (equal? (current-upstream-hub) (established-upstream-hub))) (unsubscribe!) (refresh-subscription!))) (begin/dataflow (when (next-subscription-refresh) (log-info "Next subscription refresh for topic ~s will occur in ~a seconds." full-topic (/ (- (next-subscription-refresh) (current-inexact-milliseconds)) 1000.0)))) (on #:when (next-subscription-refresh) (asserted (later-than (next-subscription-refresh))) (next-subscription-refresh #f) (refresh-subscription!)) (on #:when (poll-interval-seconds) (asserted (later-than (+ (last-upstream-check) (* 1000 (or (poll-interval-seconds) 0))))) (poll-upstream!)) (during (http-listener $host-name $port) (on (web-request-get (id req) (vh host-name port) ("sub" (,sub-id ()))) (log-info "Received verification-of-intent: ~v" (web-request-header-query req)) (define challenge (dict-ref (web-request-header-query req) 'hub.challenge "")) (define lease-seconds-str (dict-ref (web-request-header-query req) 'hub.lease_seconds #f)) (if lease-seconds-str (next-subscription-refresh (+ (current-inexact-milliseconds) (* 1000.0 (shrink-lease (string->number lease-seconds-str))))) (log-warning "Upstream hub for topic ~s did not supply hub.lease_seconds" full-topic)) (web-respond/bytes! id (string->bytes/utf-8 challenge))) (on (web-request-incoming (id req) (vh host-name port) 'post ("sub" (,sub-id ())) $body) ;; TODO: verify the use of the shared secret (actor* (define parsed-link-headers (parse-link-headers (web-request-header-headers req))) (define upstream-hub (link-header-ref parsed-link-headers 'hub #f)) (define upstream-topic (link-header-ref parsed-link-headers 'self #f)) (define content-type (web-request-header-content-type req)) (log-info "Remote topic ~a got ~v message ~v; upstream hub ~v, topic ~v" full-topic content-type body upstream-hub upstream-topic) (current-content-hash (sha1 (open-input-bytes body))) (current-content-type content-type) (current-upstream-hub upstream-hub) (send! (notification full-topic upstream-hub upstream-topic body content-type)) (web-respond/status! id 201 #"Created"))))))