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Ensure patched assertions are added before being removed, to avoid glitching

fruit
Tony Garnock-Jones 4 years ago
parent
commit
bc4fb5ef94
  1. 4
      syndicate/HOWITWORKS.md
  2. 5
      syndicate/dataspace.rkt
  3. 4
      syndicate/examples/box-and-client.rkt

4
syndicate/HOWITWORKS.md

@ -458,6 +458,10 @@ check followed by zero or more (move, check) pairs. @@ -458,6 +458,10 @@ check followed by zero or more (move, check) pairs.
removeAssertion :: Index -> V -> 1
removeAssertion index v = adjustAssertion index v -1
Care must be taken when applying entire *patches* to ensure that added
assertions are processed before removed assertions; otherwise, actors
will observe glitching in certain cases.
**Definition.** The procedure `sendMessage` delivers a message `v` to
event handlers in the given index.

5
syndicate/dataspace.rkt

@ -368,15 +368,18 @@ @@ -368,15 +368,18 @@
;; (for [((a c) (in-bag/count ds-assertions))] (log-info " . ~v = ~v" a c))
;; (for [((a c) (in-bag/count delta))] (log-info " → ~v = ~v" a c))
(define rt (dataspace-routing-table ds))
(define pending-removals '())
(define new-cleanup-changes
(for/fold [(cleanup-changes (actor-cleanup-changes ac))] [((a count) (in-bag/count delta))]
(match (bag-change! ds-assertions a count)
['present->absent (remove-assertion! rt a)]
['present->absent (set! pending-removals (cons a pending-removals))]
['absent->present (add-assertion! rt a)]
;; 'absent->absent absurd
['present->present (void)]) ;; i.e. no visible change
(define-values (updated-bag _summary) (bag-change cleanup-changes a (- count)))
updated-bag))
(for [(a (in-list pending-removals))]
(remove-assertion! rt a))
(set-actor-cleanup-changes! ac new-cleanup-changes)))
(define (run-scripts! ds)

4
syndicate/examples/box-and-client.rkt

@ -16,4 +16,6 @@ @@ -16,4 +16,6 @@
(log-info "client: box has gone"))
(on (asserted (box-state $v))
(log-info "client: learned that box's value is now ~v" v)
(send! (set-box (+ v 1)))))
(send! (set-box (+ v 1))))
(on (retracted (box-state _))
(log-info "client: box state disappeared")))

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