update codes for circuit_breaker

resiliency/06_circuit_breaker/circuit_breaker.go

@@ -3,7 +3,7 @@
  * @Author: Edward
  * @Date: 2020-05-10 22:00:58
  * @Last Modified by: Edward
- * @Last Modified time: 2020-05-21 17:41:46
+ * @Last Modified time: 2020-05-22 14:22:42
  */
 
 package circuit
@@ -33,23 +33,6 @@ const (
 	defaultSuccessThreshold = 2
 )
 
-////////////////////////////////
-/// 状态计数器 用以维护断路器内部的状态
-/// 无论是对象式断路器还是函数式断路器
-/// 都要用到计数器
-////////////////////////////////
-
-//State  断路器本身的状态的
-//State  of switch int
-type State int
-
-// state for breaker
-const (
-	StateClosed State = iota //默认的闭合状态，可以正常执行业务
-	StateHalfOpen
-	StateOpen
-)
-
 ////////////////////////////////
 //way 1 对象式断路器
 ////////////////////////////////

resiliency/06_circuit_breaker/circuit_conter.go

@@ -3,24 +3,33 @@
  * @Author: Edward
  * @Date: 2020-05-22 12:41:54
  * @Last Modified by: Edward
- * @Last Modified time: 2020-05-22 12:41:54
+ * @Last Modified time: 2020-05-22 14:21:00
  */
 
 package circuit
 
 import "time"
 
+////////////////////////////////
+/// 计数器 用以维护断路器内部的状态
+/// 无论是对象式断路器还是函数式断路器
+/// 都要用到计数器
+////////////////////////////////
+
+//State  断路器本身的状态的
+//State  of switch int
+type State int
+
+// state for breaker
+const (
+	StateClosed State = iota //默认的闭合状态，可以正常执行业务
+	StateHalfOpen
+	StateOpen
+)
+
 //OperationState of current 某一次操作的结果状态
 type OperationState int
 
-//states of CircuitBreaker
-//states: closed --->open ---> half open --> closed
-const (
-	UnknownState OperationState = iota
-	FailureState
-	SuccessState
-)
-
 //ICounter interface
 type ICounter interface {
 	Count(OperationState)

resiliency/06_circuit_breaker/circuit_func_closure.go

@@ -3,7 +3,7 @@
  * @Author: Edward
  * @Date: 2020-05-22 12:42:34
  * @Last Modified by: Edward
- * @Last Modified time: 2020-05-22 12:42:34
+ * @Last Modified time: 2020-05-22 14:35:00
  */
 
 package circuit
@@ -17,80 +17,55 @@ import (
 //way 2 简单的函数式断路器
 // 一个func实例作为一个Breaker 允许多个worker(即goroutine)同时访问
 // 理论上讲也需要考虑同步问题
+// 当前的设计思路，非常简单：
+//     1、不考虑三种状态之间的转换，只靠两种状态，电路打开与电路关闭
+//     2、当累计失败到达一定失败次数就端开请求(打开电路)，并延迟一定的时间再允许请求
 ////////////////////////////////
 
+//states of CircuitBreaker
+//states: closed --->open ---> half open --> closed
+const (
+	UnknownState OperationState = iota
+	FailureState
+	SuccessState
+)
+
 //Circuit of action stream,this is actually to do something.
 //Circuit hold the really action
 type Circuit func(context.Context) error
 
-//Breaker return a closure wrapper to hold request,达到指定的失败次数后电路断开
+var canRetry = func(cnt counters, failureThreshold uint32) bool {
+	backoffLevel := cnt.ConsecutiveFailures - failureThreshold
+	// Calculates when should the circuit breaker resume propagating requests
+	// to the service
+	shouldRetryAt := cnt.LastActivity().Add(time.Second << backoffLevel)
+	return time.Now().After(shouldRetryAt)
+}
+
+//Breaker return a closure wrapper to hold request
 func Breaker(c Circuit, failureThreshold uint32) Circuit {
 
-	//内部计数器
+	//闭包内部的全局计数器 和状态标志
 	cnt := counters{}
-	expired := time.Now()
-	currentState := StateClosed //默认是闭合状态
 
 	//ctx can be used hold parameters
 	return func(ctx context.Context) error {
 
 		if cnt.ConsecutiveFailures >= failureThreshold {
-
+			if !canRetry(cnt, failureThreshold) {
-			//断路器在half open状态下的控制逻辑
-			canRetry := func(cnt counters) bool {
-				//间歇时间，多个线程时候会存在同步文件需要lock操作
-				backoffLevel := cnt.ConsecutiveFailures - failureThreshold
-				// Calculates when should the circuit breaker resume propagating requests
-				// to the service
-				shouldRetryAt := cnt.LastActivity().Add(time.Second << backoffLevel)
-				return time.Now().After(shouldRetryAt)
-			}
-
-			//如果仍然不能执行，直接返回失败
-			if !canRetry(cnt) {
 				// Fails fast instead of propagating requests to the circuit since
 				// not enough time has passed since the last failure to retry
 				return ErrServiceUnavailable
 			}
 		}
-
-		// 可以执行，则执行，并累计成功和失败次数
 		// Unless the failure threshold is exceeded the wrapped service mimics the
 		// old behavior and the difference in behavior is seen after consecutive failures
-		// do the job
+		if err := c(ctx); err != nil {
-
+			cnt.Count(FailureState)
-		//handle statue transformation for timeout
+			return err
-		if currentState == StateOpen {
-			nowt := time.Now()
-			if expired.Before(nowt) || expired.Equal(nowt) {
-				currentState = StateHalfOpen //端开状态的计时器过期了，转为半开
-				cnt.ConsecutiveSuccesses = 0 //重置用于累计成功调用的计数器
-			}
 		}
 
-		switch currentState {
+		cnt.Count(SuccessState)
-		case StateOpen:
-			return ErrServiceUnavailable //直接失败
-		case StateHalfOpen:
-			if err := c(ctx); err != nil {
-				//统计状态
-				cnt.Count(FailureState)
-				currentState = StateOpen
-				expired = time.Now().Add(defaultTimeout) //Reset默认的超时时间
-				return err
-			}
-			//统计成功状态
-			cnt.Count(SuccessState)
-			//处理状态转换
-			if cnt.ConsecutiveSuccesses > defaultSuccessThreshold {
-				currentState = StateClosed
-				cnt.ConsecutiveFailures = 0
-			}
-			return nil
-
-		case StateClosed:
-
-		}
 		return nil
 	}
 }