Methods to stop a loop from executing.

control-loop.clj

(defn ping-forever-core-async
  [host ms-pause]
  (let [termination-ch (chan)
        termination-fn #(put! termination-ch :die)]
    (go-loop [sleep-ch (timeout 0)]
      (let [[_ ch] (alts! [sleep-ch termination-ch])]
        (if (= ch sleep-ch)
          (do
            (println "Pinging" host)
            (recur (timeout ms-pause)))
          (println "Stopping..."))))
    termination-fn))

(defn ping-forever-thread
  [host ms-pause]
  (let [t (Thread. #(try
                     (while true
                       (println "Pinging " host)
                       (Thread/sleep ms-pause))
                     (catch InterruptedException e
                       (println "Stopping..."))))
        termination-fn #(.interrupt t)]
    (.start t)
    termination-fn))

(defn ping-forever-flag
  [host ms-pause]
  (let [keep-going (atom true)
        stop-fn #(reset! keep-going false)]
    (future (while @keep-going
              (println "Pinging" host)
              (Thread/sleep ms-pause))
            (println "Stopping..."))
    stop-fn))