Skip to content

Instantly share code, notes, and snippets.

Embed
What would you like to do?
; STM history stress-test
(defn stress [hmin hmax]
(let [r (ref 0 :min-history hmin :max-history hmax)
slow-tries (atom 0)]
(future
(dosync
(swap! slow-tries inc)
(Thread/sleep 200)
@r)
(println "a is:" @r "history:" (.getHistoryCount r)
"after:" @slow-tries "tries"))
(dotimes [i 500]
(Thread/sleep 10)
(dosync (alter r inc)))
:done))
(stress 0 10) ; default ref settings
;=> :done
; a is: 500 history: 10 after: 26 tries
; This indicates that the slow transaction never succeeded until the dotimes
; loop was complete (and returned :done)
(stress 0 30)
; a is: 415 history: 19 after: 21 tries
;=> :done
; Here the slow transaction completed first, after growing the history to 19.
; Success! But it took 21 tries to grow the history from 0, so we can help out
; by starting with a larger min-history:
(stress 15 30)
; a is: 119 history: 20 after: 6 tries
;=> :done
; Only 6 retries of the slow transaction this time, enough to grow the history
; from 15 to 20.
@ghoseb

This comment has been minimized.

Copy link
Owner Author

commented May 31, 2013

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
You can’t perform that action at this time.