mirror of
https://github.com/crazybber/go-pattern-examples.git
synced 2024-11-22 11:56:03 +03:00
97 lines
2.8 KiB
Go
97 lines
2.8 KiB
Go
/*
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* @Description: https://github.com/crazybber
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* @Author: Edward
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* @Date: 2020-05-22 12:42:34
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* @Last Modified by: Edward
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* @Last Modified time: 2020-05-22 12:42:34
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*/
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package circuit
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import (
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"context"
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"time"
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)
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////////////////////////////////
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//way 2 简单的函数式断路器
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// 一个func实例作为一个Breaker 允许多个worker(即goroutine)同时访问
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// 理论上讲也需要考虑同步问题
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////////////////////////////////
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//Circuit of action stream,this is actually to do something.
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//Circuit hold the really action
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type Circuit func(context.Context) error
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//Breaker return a closure wrapper to hold request,达到指定的失败次数后电路断开
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func Breaker(c Circuit, failureThreshold uint32) Circuit {
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//内部计数器
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cnt := counters{}
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expired := time.Now()
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currentState := StateClosed //默认是闭合状态
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//ctx can be used hold parameters
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return func(ctx context.Context) error {
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if cnt.ConsecutiveFailures >= failureThreshold {
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//断路器在half open状态下的控制逻辑
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canRetry := func(cnt counters) bool {
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//间歇时间，多个线程时候会存在同步文件需要lock操作
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backoffLevel := cnt.ConsecutiveFailures - failureThreshold
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// Calculates when should the circuit breaker resume propagating requests
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// to the service
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shouldRetryAt := cnt.LastActivity().Add(time.Second << backoffLevel)
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return time.Now().After(shouldRetryAt)
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}
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//如果仍然不能执行，直接返回失败
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if !canRetry(cnt) {
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// Fails fast instead of propagating requests to the circuit since
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// not enough time has passed since the last failure to retry
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return ErrServiceUnavailable
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}
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}
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// 可以执行，则执行，并累计成功和失败次数
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// Unless the failure threshold is exceeded the wrapped service mimics the
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// old behavior and the difference in behavior is seen after consecutive failures
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// do the job
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//handle statue transformation for timeout
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if currentState == StateOpen {
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nowt := time.Now()
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if expired.Before(nowt) || expired.Equal(nowt) {
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currentState = StateHalfOpen //端开状态的计时器过期了，转为半开
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cnt.ConsecutiveSuccesses = 0 //重置用于累计成功调用的计数器
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}
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}
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switch currentState {
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case StateOpen:
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return ErrServiceUnavailable //直接失败
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case StateHalfOpen:
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if err := c(ctx); err != nil {
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//统计状态
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cnt.Count(FailureState)
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currentState = StateOpen
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expired = time.Now().Add(defaultTimeout) //Reset默认的超时时间
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return err
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}
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//统计成功状态
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cnt.Count(SuccessState)
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//处理状态转换
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if cnt.ConsecutiveSuccesses > defaultSuccessThreshold {
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currentState = StateClosed
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cnt.ConsecutiveFailures = 0
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}
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return nil
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case StateClosed:
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}
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return nil
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}
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}
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