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|
#lang racket/base
(require racket/match
racket/contract)
(require "manager.rkt"
web-server/http
web-server/servlet/servlet-structs)
(provide/contract
[create-LRU-manager
(->
(or/c false/c
(request? . -> . can-be-response?))
number? number? (-> boolean?)
#:initial-count number?
#:inform-p (number? . -> . void)
manager?)]
[make-threshold-LRU-manager
(->
(or/c false/c
(request? . -> . can-be-response?))
number?
manager?)])
;; Utility
(define (make-counter)
(define i 0)
(lambda ()
(set! i (add1 i))
i))
; Copied from InstaServlet, which copied from Continue (I believe?)
(define (make-threshold-LRU-manager instance-expiration-handler
memory-threshold)
(create-LRU-manager
;; Called when an instance has expired.
instance-expiration-handler
;; The condition below is checked every 5 seconds
5
;; One 'life point' is deducted every 10 minutes
(* 10 60)
;; If this condition is true a 'life point' is deducted
;; from the continuation
(lambda ()
(define memory-use (current-memory-use))
(define collect? (or (>= memory-use memory-threshold)
(< memory-use 0)))
collect?)
;; The number of 'life points' an continuation starts with
#:initial-count 24
;; Logging done whenever an continuation is collected
#:inform-p (lambda args
(void))))
(define-struct (LRU-manager manager) (instance-expiration-handler
; Private
instances
next-instance-id))
(define (create-LRU-manager
instance-expiration-handler
check-interval collect-interval
collect?
#:initial-count [initial-count 1]
#:inform-p [inform-p (lambda _ (void))])
(define lock (make-semaphore 1))
;; Instances
(define instances (make-hasheq))
(define next-instance-id (make-counter))
(define-struct instance (k-table))
(define (create-instance expire-fn)
(define instance-id (next-instance-id))
(hash-set! instances
instance-id
(make-instance (create-k-table)))
instance-id)
(define (adjust-timeout! instance-id secs)
(void))
(define (instance-lookup instance-id)
(define instance
(hash-ref instances instance-id
(lambda ()
(raise (make-exn:fail:servlet-manager:no-instance
(format "No instance for id: ~a" instance-id)
(current-continuation-marks)
instance-expiration-handler)))))
instance)
;; Continuation table
(define-struct k-table (next-id-fn htable))
(define (create-k-table)
(make-k-table (make-counter) (make-hasheq)))
;; Interface
(define (clear-continuations! instance-id)
(match (instance-lookup instance-id)
[(struct instance ((and k-table (struct k-table (next-id-fn htable)))))
(hash-for-each
htable
(match-lambda*
[(list k-id (list salt k expiration-handler count))
(hash-set! htable k-id
(list salt #f expiration-handler count))]))]))
(define (continuation-store! instance-id k expiration-handler)
(match (instance-lookup instance-id)
[(struct instance ((struct k-table (next-id-fn htable))))
(define k-id (next-id-fn))
(define salt (random 100000000))
(hash-set! htable
k-id
(list salt k expiration-handler initial-count))
(list k-id salt)]))
(define (continuation-lookup* instance-id a-k-id a-salt peek?)
(match (instance-lookup instance-id)
[(struct instance ((struct k-table (next-id-fn htable))))
(match
(hash-ref htable a-k-id
(lambda ()
(raise (make-exn:fail:servlet-manager:no-continuation
(format "No continuation for id: ~a" a-k-id)
(current-continuation-marks)
instance-expiration-handler))))
[(list salt k expiration-handler count)
(unless peek?
(hash-set! htable a-k-id
(list salt k expiration-handler (add1 count))))
(if (or (not (eq? salt a-salt))
(not k)
(and (custodian-box? k)
(not (custodian-box-value k))))
(raise (make-exn:fail:servlet-manager:no-continuation
(format "No continuation for id: ~a" a-k-id)
(current-continuation-marks)
(if expiration-handler
expiration-handler
instance-expiration-handler)))
k)])]))
(define (continuation-lookup instance-id a-k-id a-salt)
(continuation-lookup* instance-id a-k-id a-salt #f))
(define (continuation-peek instance-id a-k-id a-salt)
(continuation-lookup* instance-id a-k-id a-salt #t))
(define (wrap f)
(lambda args
(call-with-semaphore lock (lambda () (apply f args)))))
(define the-manager
(make-LRU-manager (wrap create-instance)
adjust-timeout!
(wrap clear-continuations!)
(wrap continuation-store!)
(wrap continuation-lookup)
(wrap continuation-peek)
; Specific
instance-expiration-handler
; Private
instances
next-instance-id))
; Collector
(define (collect just-go?)
(call-with-semaphore
lock
(lambda ()
(define removed (box 0))
(hash-for-each
instances
(match-lambda*
[(list instance-id (struct instance ((struct k-table (next-id-fn htable)))))
(define empty? (box #t))
(hash-for-each
htable
(match-lambda*
[(list k-id (list s k eh count))
(if (zero? count)
(begin (set-box! removed (add1 (unbox removed)))
(hash-remove! htable k-id))
(begin (set-box! empty? #f)
(hash-set! htable k-id
(list s k eh (sub1 count)))))]))
(when (unbox empty?)
(set-box! removed (add1 (unbox removed)))
(hash-remove! instances instance-id))]))
(when (or just-go?
(not (zero? (unbox removed))))
(inform-p (unbox removed))
(collect-garbage)
(collect-garbage)))))
(define manager-thread
(thread
(lambda ()
(define (seconds->msecs s)
(+ (current-inexact-milliseconds)
(* s 1000)))
(let loop ([msecs0 (seconds->msecs check-interval)]
[msecs1 (seconds->msecs collect-interval)])
(sync (handle-evt
(alarm-evt msecs0)
(lambda _
(when (collect?)
(collect #f))
(loop (seconds->msecs check-interval) msecs1)))
(handle-evt
(alarm-evt msecs1)
(lambda _
(collect #t)
(loop msecs0 (seconds->msecs collect-interval)))))))))
the-manager)
|
