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Tweak the resource pool return behaviour

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If there's lots of contention for the resource pool, there will be lots of
waiters, so telling all of them to retry whenever a resource is returned seems
wasteful. This commit adds a new option (assume-reliable-waiters?) which will
have the resource pool try to give a returned resource to the oldest waiter,
if this fails, it'll go back to the old behaviour of telling all waiters to
retry.
This commit is contained in:
Christopher Baines 2024-10-31 16:46:43 +00:00
parent de5e036ab1
commit af93bdcf5e
1 changed files with 76 additions and 25 deletions
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61
guix-data-service/utils.scm
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@ -121,7 +121,8 @@
destructor
lifetime
scheduler
(name "unnamed"))
(name "unnamed")
assume-reliable-waiters?)
(define (initializer/safe)
(with-exception-handler
(lambda (exn)
@ -245,9 +246,59 @@
waiters
resources-last-used)))))
(('return resource)
;; When a resource is returned, prompt all the waiters to request
;; again. This is to avoid the pool waiting on channels that may
;; be dead.
(if (and assume-reliable-waiters?
(not (null? waiters)))
(let ((checkout-success?
(perform-operation
(choice-operation
(wrap-operation
(put-operation (last waiters)
resource)
(const #t))
(wrap-operation (sleep-operation 1)
(const #f))))))
(unless checkout-success?
(set! checkout-failure-count
(+ 1 checkout-failure-count)))
(if checkout-success?
(loop resources
available
(drop-right! waiters 1)
(begin
(list-set!
resources-last-used
(list-index (lambda (x)
(eq? x resource))
resources)
(get-internal-real-time))
resources-last-used))
(begin
(for-each
(lambda (waiter)
(spawn-fiber
(lambda ()
(perform-operation
(choice-operation
(put-operation waiter 'resource-pool-retry-checkout)
(sleep-operation 0.2))))))
waiters)
(loop resources
(cons resource available)
'()
(begin
(list-set!
resources-last-used
(list-index (lambda (x)
(eq? x resource))
resources)
(get-internal-real-time))
resources-last-used)))))
(begin
;; When a resource is returned, prompt all the waiters
;; to request again. This is to avoid the pool waiting
;; on channels that may be dead.
(for-each
(lambda (waiter)
(spawn-fiber
@ -269,7 +320,7 @@
(eq? x resource))
resources)
(get-internal-real-time))
resources-last-used)))
resources-last-used)))))
(('stats reply)
(let ((stats
`((resources . ,(length resources))