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Worker Queues in Clojure
In Rich Hickey's talk "Making simple easy" he recommends decoupling things so that if "A" wants to call a function in "B" there should be a queue of some kind in between so that A & B don't have to be aware of each other's existence. He calls this "complecting the when and the who", ie introducing unnecessary complexity.
So, how to implement in clojure? Here's my stab at it:
(defn new-q [] (java.util.concurrent.LinkedBlockingDeque.))
(defn offer!
"adds x to the back of queue q"
[q x] (.offer q x) q)
(defn take!
"takes from the front of queue q. if q is empty, block until something is offer!ed into it"
[q] (.take q))
;; so now we can do like this
(def example-queue (new-q))
(future (println ">> " (take! q))) ; background thread, blocks waiting for something to print
(offer! q "HELLO WORLD") ; now the future-d thread is unblocked and ">> HELLO WORLD" is printed.
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