Initial stab at a general supervisor
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#lang syndicate/actor
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;; Extremely simple single-actor supervision
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;; Vastly simplified compared to the available options in OTP
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(provide supervise)
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(require racket/exn)
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(require "core.rkt")
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(require "dataflow.rkt")
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(require "hierarchy.rkt")
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(require "store.rkt")
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(require (submod "actor.rkt" implementation-details))
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(require/activate "drivers/timestate.rkt")
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(define-syntax-rule (supervise expr ...)
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(supervise* (lambda () expr ...)))
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(define (supervise* actor-producing-thunk)
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(with-store [(current-action-transformer (supervise-spawn (current-action-transformer)))]
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(actor-producing-thunk)))
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(define ((supervise-spawn previous-action-transformer) ac)
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(match (previous-action-transformer ac)
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[(? spawn? s) (supervise** s)]
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[other other]))
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(define (supervise** s)
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(make-spawn (lambda ()
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;; TODO: Consider closing supervisor-main over s
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;; rather than over st0 and acs. That way, effects
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;; from spawn->process+transition will reappear at
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;; each reboot.
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;;
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;; %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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;; %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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;; BUG: Exception thrown inside
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;; spawn->process+transition will kill the supervisor!
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;; %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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;; %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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;;
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(define-values (proc initial-transition) (spawn->process+transition s))
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(log-info "spawn->process+transition complete: ~v" proc)
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(match initial-transition
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[(transition st0 acs)
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(list actor-behavior
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(boot-actor (lambda ()
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(react
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(supervisor-main proc st0 acs))))
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(list 'supervised (process-name proc)))]
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[other
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(list (process-behavior proc)
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other
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(list 'supervised (process-name proc)))]))))
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(define (supervisor-main proc boot-state boot-actions)
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(field [done? #f])
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(stop-when (rising-edge (done?)))
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(field [should-run? #f]
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[ready? #f])
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(define inner-handle-event (process-behavior proc))
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(define intensity 1)
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(define period 5000) ;; milliseconds
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(define sleep-time 10) ;; seconds
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(field [restarts '()])
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(define (add-restart!)
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(define now (current-inexact-milliseconds))
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(define oldest-to-keep (- now period))
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(restarts (filter (lambda (r) (>= r oldest-to-keep))
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(cons (current-inexact-milliseconds) (restarts))))
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(when (> (length (restarts)) intensity)
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(log-error "Supervised process ~v ~a reached max restart intensity. Sleeping for ~a seconds"
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(process-name proc)
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(current-actor-path)
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sleep-time)
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(sleep sleep-time)))
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(on (rising-edge (not (ready?)))
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(should-run? #f)
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(retract! ?)
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(flush!)
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(should-run? #t))
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(on (rising-edge (should-run?))
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(react (stop-when (rising-edge (not (should-run?))))
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(field [inner-state boot-state])
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(on-start (perform-actions! boot-actions)
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(ready? #t))
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(on-event
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[e (with-handlers ([(lambda (exn) #t)
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(lambda (e)
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(log-error "Supervised process ~v ~a died with exception:\n~a"
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(process-name proc)
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(current-actor-path)
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(if (exn? e)
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(exn->string e)
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(format "~v" e)))
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(add-restart!)
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(ready? #f))])
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(match (inner-handle-event e (inner-state))
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[#f (void)] ;; N.B. TODO: Polling (event of #f)
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;; will never reach the inner actor, since
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;; actor-behavior doesn't bother executing anything
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;; if it is given #f.
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[(<quit> _ acs) (perform-actions! acs) (done? #t)]
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;; N.B. TODO: what to do with the exception carried
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;; in the quit struct?
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[(transition st acs) (perform-actions! acs) (inner-state st)]))]))))
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;; BROKENish APPROACH: See uni.org (search for 30048bda-b5c2-11e6-afe4-73eb3e5180cc)
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;; (define (supervisor-main proc boot-state boot-actions)
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;; (field [done? #f])
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;; (stop-when (rising-edge (done?)))
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;; (log-info "ORIGINAL: ~v ~v" (process-name proc) boot-state)
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;; (define inner-handle-event (process-behavior proc))
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;; (field [inner-state boot-state] [running? #t])
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;; (on-start (perform-actions! boot-actions))
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;; (define (reboot!)
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;; (log-info "--------------------------------------------------")
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;; (running? #f)
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;; (retract! ?)
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;; ;; (flush!)
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;; (inner-state boot-state)
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;; (log-info "--------------------------------------------------")
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;; (running? #t)
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;; (log-info "REBOOT: ~v ~v" (process-name proc) boot-state)
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;; (perform-actions! boot-actions))
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;; (define intensity 1)
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;; (define period 5000) ;; milliseconds
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;; (define sleep-time 10) ;; seconds
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;; (field [restarts '()])
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;; (define (add-restart!)
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;; (define now (current-inexact-milliseconds))
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;; (define oldest-to-keep (- now period))
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;; (restarts (filter (lambda (r) (>= r oldest-to-keep))
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;; (cons (current-inexact-milliseconds) (restarts))))
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;; (when (> (length (restarts)) intensity)
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;; (log-error "Supervised process ~v ~a reached max restart intensity. Sleeping for ~a seconds"
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;; (process-name proc)
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;; (current-actor-path)
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;; sleep-time)
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;; (sleep sleep-time)))
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;; (on-event [e (when (running?)
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;; (with-handlers ([(lambda (exn) #t)
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;; (lambda (e)
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;; (log-error "Supervised process ~v ~a died with exception:\n~a"
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;; (process-name proc)
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;; (current-actor-path)
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;; (if (exn? e)
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;; (exn->string e)
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;; (format "~v" e)))
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;; (add-restart!)
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;; (reboot!))])
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;; (match (inner-handle-event e (inner-state))
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;; [#f (void)] ;; N.B. TODO: Polling (event of #f)
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;; ;; will never reach the inner actor, since
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;; ;; actor-behavior doesn't bother executing anything
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;; ;; if it is given #f.
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;; [(<quit> _ acs) (perform-actions! acs) (done? #t)]
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;; ;; N.B. TODO: what to do with the exception carried
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;; ;; in the quit struct?
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;; [(transition st acs) (perform-actions! acs) (inner-state st)])))]))
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