Function with Retry

gistfile1.txt

;; Returns a function with retries.
;; retries: num of retries
;; delay: delay between retries in milliseconds
;; f: function to apply
;; ef: error function, determines if f should be retried
;; f and ef should not throw Exceptions

(defn with-retry
  [retries delay f ef]
  (fn [& args]
    (loop [retry 1]
      (let [result (apply f args)]
        (if (and (ef result) (<= retry retries))
          (do (Thread/sleep delay)
              (recur (inc retry)))
          result)))))
          
;; 
;; (f) will retry 5 times with a 2 second delay and finally return {:error true}
;; (def f (with-retry 5 2000 (fn [] {:error true}) :error))
;;
;; (g) will run successfully on the first attempt
;; (def g (with-retry 5 2000 (fn [] {:x 1 :y 2}) :error))