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(ns scheduled-agent
(:import java.util.concurrent.Executors
java.util.concurrent.TimeUnit)
(:use clojure.stacktrace))
(defn- runnable-proxy [f]
(proxy [Runnable] [] (run [] (f))))
(defn scheduled-agent
[func period init]
(let [pool (Executors/newScheduledThreadPool 1)
data (ref init)
pfunc (runnable-proxy (fn []
(try
(let [val (func)]
(dosync (ref-set data val)))
(catch Exception e
(print-stack-trace e 5)))))
future (.scheduleWithFixedDelay pool pfunc 0 period TimeUnit/SECONDS)]
{:pool pool
:data data
:future future
:func func
:period period
:init init}))
(defn poll [{d :data}]
"Return current contents of agent."
@d)
(defn cancel! [{f :future}]
"Cancel automatic updating of agent data. Cannot be restarted."
(.cancel f false))
(defn update! [{func :func data :data}]
"Synchronously update contents of agent."
(let [val (func)]
(dosync
(ref-set data val))))
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