Hello,
I had a problem when I run the following code:
(defn get-task [tasks]
(dosync
(let [task (first @tasks)]
(alter tasks rest)
task)))
(defn worker [& {:keys [tasks]}]
(agent {:tasks tasks}))
(defn worker-loop [{:keys [tasks] :as state}]
(loop [last-task nil]
(if-let [task (get-task tasks)]
(recur task)
(locking :out (println "Last task: " last-task))))
state)
(defn create-workers [count & options]
(->> (range 0 count)
(map (fn [_] (apply worker options)))
(into [])))
(defn start-workers [workers]
(doseq [worker workers] (send-off worker worker-loop)))
(def tasks (ref (range 1 10000000)))
(def workers (create-workers 100 :tasks tasks))
(start-workers workers)
(apply await workers)
Description: I have several agents (100 in my case). Each agent running in
a separate thread. All agents share the one ref with the collection of
tasks (range of longs in my case). Each agent get tasks from the collection
(in transaction) one by one until the collection becomes empty and then
prints the last task which it handle. However, when I run this code it
looks like the collection of tasks suddenly becomes empty and workers
handle only portion of all tasks (average 25-40% of all number).
This code behave as I expected, when I create only one agent or use
explicit locking in get-task function:
(defn get-task [tasks]
(locking :lock
(dosync
(let [task (first @tasks)]
(alter tasks rest)
task))))
I run this code on the Clojure 1.8.0
java version "1.8.0_91"
Java(TM) SE Runtime Environment (build 1.8.0_91-b14)
Java HotSpot(TM) 64-Bit Server VM (build 25.91-b14, mixed mode)
Can anyone tell me, what am I doing wrong, or it really looks like a bug in
the clojure STM?
I already asked this question on stackoverflow.com (
http://stackoverflow.com/questions/39054911/strange-behavior-of-clojure-ref),
but so far nobody has been able to help me.
P.S. Sorry for my english skill.
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