breaker-part-1.clj

(ns org.higher-order.integration.circuit-breaker.atomic
  (:use org.higher-order.integration.circuit-breaker.states)
  (:gen-class))

(def default-policy (TransitionPolicy 5 5000))
(def initial-state (ClosedState default-policy 0))

(def state (atom initial-state))

(def transition-by!)

(defn wrap [f]
  (fn [& args]
    (let [s (transition-by! on-before-call)]
      (if (proceed s)
	(try 
	 (let [res (apply f args)]
	   (do (transition-by! on-success)
	       res))
	 (catch Exception e
	   (do 
	     (transition-by! on-error)
	     (throw e))))
	(throw (java.lang.RuntimeException. "OpenCircuit"))))))

(defn transition-by! [f]
  (loop [s @state
	 t (f s)]
    (cond 
      (identical? s t) s
      (compare-and-set! state s t) t
      :else (let [s1 @state
		  t1 (f s1)]
	      (recur s1 t1)))))