> On Jun 14, 2019, at 8:15 PM, Matthew Butterick <m...@mbtype.com> wrote:
>
> But even after approving a lock request from a certain rendering place, the
> lock server would end up with repeat lock requests from there.
BTW here's a minimal example showing the puzzling message-garbling behavior
between places.
Here, instead of a lock server, I just have a loopback server. What I expect is
that each worker sends a request number, and the loopback immediately echoes
this number back as a response, so the numbers will always match.
But that's not what happens. At first, the response numbers match the requests.
But then they start coming back mismatched. The error rate increases as the
`sleep` value decreases, for instance:
worker request 1:46 got response 1:46
worker request 0:90 got response 0:90
worker request 0:91 got response 2:31 ### fail
worker request 2:31 got response 0:91 ### fail
worker request 7:12 got response 7:12
worker request 1:47 got response 1:47
worker request 4:19 got response 0:92 ### fail
worker request 0:92 got response 4:19 ### fail
worker request 5:16 got response 5:16
worker request 0:93 got response 0:93
The garbling happens in a predictable way: every request is answered, but a
closely occurring set of requests and responses will be mismatched among
themselves. By adjusting the `sleep` value, it's easy to create a flow rate of
messages where almost all of them are garbled.
#lang racket
(provide main)
(define (main)
(define loopback-p
(place ch
(let loop ()
(place-channel-put ch (place-channel-get ch))
(loop))))
(define worker-ps
(for/list ([i (in-range (processor-count))])
(place ch
(match-define (list loopback-p wpidx) (place-channel-get ch))
(let make-request ([count 1])
(match-define (list wpidxout countout)
(place-channel-put/get loopback-p (list wpidx count)))
(displayln (format "worker request ~a:~a got response ~a:~a ~a"
wpidx count wpidxout countout
(if (and (eq? wpidx wpidxout) (eq? count
countout)) "" "### fail")))
(sleep (* 0.01 (add1 wpidx))) ; multiplier makes workers go at
different speeds
(make-request (add1 count))))))
(for ([(wp wpidx) (in-indexed worker-ps)])
(place-channel-put wp (list loopback-p wpidx)))
(map place-wait worker-ps))
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