minimum wait queue

concdemo.clj

(ns wn-backend.concdemo
  (:require [wn-backend.util.common :refer :all]
            [clj-http.client :as client])
  (:import [java.util.concurrent LinkedBlockingQueue]))

(def my-queue (LinkedBlockingQueue.))

(def queue-minimum-delay 1000)

(defn queue-processor []
  (loop []
    (debugp "waiting on queue" true)
    (let [item (.take my-queue)]
      (debugp "took item from queue" item)
      (deliver (:promise item)
               (client/get (:url item))))
    (Thread/sleep queue-minimum-delay)
    (when-not (Thread/interrupted)
      (recur))))

(defn wait-for-request [url]
  (let [delivery-promise (promise)]
    ;; This will never error or block.
    (.add my-queue
          {:url url
           :promise delivery-promise})
    (-> delivery-promise deref)))
  

(defn foo []
  (wait-for-request "http://www.example.com/"))

(def processor-handle (atom nil))

(defn start-queue! []
  (reset! processor-handle (future (queue-processor))))

(defn stop-queue! []
  ;; XXX return value?
  (future-cancel @processor-handle))