A first attempt at a polling loop in clojure...

wait-for.clj

;; Based on a queue polling function from Chas Emerick's bandalore:
;;     https://github.com/cemerick/bandalore/blob/master/src/main/clojure/cemerick/bandalore.clj#L124

(defn wait-for
 "Invoke predicate every interval (default 10) seconds until it returns true,
  or timeout (default 150) seconds have elapsed. E.g.:

      (wait-for #(< (rand) 0.2) :interval 1 :timeout 10)

  Returns nil if the timeout elapses before the predicate becomes true, otherwise
  the value of the predicate on its last evaluation."
 [predicate & {:keys [interval timeout]
               :or {interval 10
                    timeout 150}}]
 (let [end-time (+ (System/currentTimeMillis) (* timeout 1000))]
   (loop []
     (if-let [result (predicate)]
       result
       (do
         (Thread/sleep (* interval 1000))
         (if (< (System/currentTimeMillis) end-time)
           (recur)))))))