mirror of
https://github.com/crazybber/go-pattern-examples.git
synced 2024-11-22 20:06:02 +03:00
135 lines
3.3 KiB
Go
135 lines
3.3 KiB
Go
/*
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* @Description: https://github.com/crazybber
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* @Author: Edward
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* @Date: 2020-05-10 22:00:58
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* @Last Modified by: Edward
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* @Last Modified time: 2020-05-22 17:25:56
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*/
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package circuit
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import (
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"context"
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"errors"
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"fmt"
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"sync"
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"time"
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)
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////////////////////////////////
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///使用HTTP请求的例子
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//每个搜索引擎时时刻刻都会遇到超大规模的请求的流量.
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//这里演示一个复杂一点的例子，同时使用Option 模式
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//ErrServiceUnavailable for error
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var (
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ErrTooManyRequests = errors.New("too many requests")
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ErrServiceUnavailable = errors.New("service unavailable")
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FailureThreshold = 10 //最大失败次数--->失败阈值
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)
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// 默认的超时时间
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const (
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defaultTimeout = time.Second * 30
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defaultSuccessThreshold = 2
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)
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////////////////////////////////
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//way 2 对象式断路器
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// 高级模式
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// 支持多工作者模式
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////////////////////////////////
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//RequestBreaker for protection
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type RequestBreaker struct {
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options Options
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mutex sync.Mutex
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state State
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generation uint64
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cnter counters
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}
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//NewRequestBreaker return a breaker
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func NewRequestBreaker(opts ...Option) *RequestBreaker {
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defaultOptions := Options{
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Name: "defaultBreakerName",
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Expiry: time.Now().Add(time.Second * 20),
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Interval: time.Second * 2, // interval to check status
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Timeout: time.Second * 60, //default to 60 seconds
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MaxRequests: 5,
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WhenToBreak: func(cnter counters) bool { return cnter.ConsecutiveFailures > 2 },
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OnStateChanged: func(name string, fromPre State, toCurrent State) {},
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}
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for _, setOption := range opts {
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setOption(&defaultOptions)
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}
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return &RequestBreaker{
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options: defaultOptions,
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cnter: counters{},
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generation: 0,
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}
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}
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// Do the given requested work if the RequestBreaker accepts it.
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// Do returns an error instantly if the RequestBreaker rejects the request.
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// Otherwise, Execute returns the result of the request.
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// If a panic occurs in the request, the RequestBreaker handles it as an error and causes the same panic again.
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func (rb *RequestBreaker) Do(work func(ctx context.Context) (interface{}, error)) (interface{}, error) {
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preState := StateUnknown
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//before
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fmt.Println("before do : request:", rb.cnter.Total())
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rb.mutex.Lock()
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switch rb.state {
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case StateOpen:
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return nil, ErrTooManyRequests
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case StateHalfOpen:
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//如果是断开状态，并且超时了，转到半开状态，记录
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if rb.options.Expiry.Before(time.Now()) {
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rb.state = StateHalfOpen
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preState = rb.state
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rb.cnter.Reset()
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}
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}
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rb.mutex.Unlock()
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//do work
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//do work from requested user
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result, err := work(rb.options.Ctx)
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rb.mutex.Lock()
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//失败了
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if err != nil {
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rb.cnter.Count(FailureState)
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//如果是在半开状态下的失败，立即打开开关
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if rb.state == StateHalfOpen {
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rb.state = StateOpen //转为打开
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} else if rb.state == StateClosed {
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if rb.options.WhenToBreak(rb.cnter) {
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rb.state = StateOpen //打开开关
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rb.cnter.Reset()
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}
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}
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} else {
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rb.cnter.Count(SuccessState)
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if preState == StateOpen && rb.state == StateHalfOpen {
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rb.options.OnStateChanged(rb.options.Name, StateOpen, StateHalfOpen)
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}
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}
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rb.mutex.Unlock()
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//after
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fmt.Println("after do : request:", rb.cnter.Total())
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return result, err
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}
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