circuit-breaker-wrap.clj

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

(defn make-circuit-breaker
  "Creates a circuit-breaker instance. If called with no arguments
a circuit-breaker in the initial closed state with the default policy is
created. If called with one argument supporting the CircuitBreakerTransitions
protocol, a circuit-breaker is created using that as state."
  ([] (atom initial-state))
  ([#^CircuitBreakerTransitions s] (atom s)))	

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