clojure transaction

(ns transaction-test
  (:refer-clojure :exclude [time]))

(def r1 (ref 0 :min-history 20))

(def base-time (System/currentTimeMillis))

(defn time []
  (- (System/currentTimeMillis) base-time))

(defn retries []
  (let [count (atom 0)]
    (dosync
     (swap! count inc)
     (Thread/sleep 1000)
     (alter r1 identity))
     ;;@r1)
     ;;(ensure r1))
    (println (format "%d retries, r1=%d" @count @r1))
    (println (str "3: " (time)))))

(println (str "1: " (time)))

(-> retries Thread. .start)

(dotimes [_ 4]
  (dosync
   (Thread/sleep 300)
   (alter r1 inc)))

(println (str "2: " (time)))

;; Example result:
;; 1: 57
;; 2: 1309
;; 3 retries, r1=4
;; 3: 3079