extending.clj

(extend 
 ::ClosedState CircuitBreakerTransitions
 (merge abs-transitions
	{:proceed    (constantly true)
	 :on-success (fn [s] (if (zero? (:fail-count s)) s (to-closed-state-from s)))
	 :on-error   (fn [s]
		       (let [p (:policy s)
			     f (:fail-count s)]
			 (if (= f (:fail-count p))
			   (OpenState p (System/currentTimeMillis))
			   (assoc s :fail-count (inc f)))))}))

(extend 
 ::OpenState CircuitBreakerTransitions
 (merge abs-transitions
	{:on-success (fn [s] (InitialHalfOpenState (:policy s)))
	 :on-before-call (fn [s] 
			   (let [p (:policy s)
				 delta (- (System/currentTimeMillis) (:time-stamp s))]
			     (if (> delta (:timeout p)) 
			       (InitialHalfOpenState p)
			       s)))}))

(extend 
 ::InitialHalfOpenState CircuitBreakerTransitions
 (merge abs-transitions
	{:proceed (constantly true)
	 :on-before-call (fn [s] (PendingHalfOpenState (:policy s)))
	 :on-success     to-closed-state-from
	 :on-error       (fn [s] (OpenState (:policy s) (System/currentTimeMillis)))}))

(extend 
 ::PendingHalfOpenState
 CircuitBreakerTransitions
 (merge abs-transitions
	{:on-success to-closed-state-from
	 :on-error (fn [s] (OpenState (:policy s) (System/currentTimeMillis)))}))