mirror of
https://github.com/crazybber/go-pattern-examples.git
synced 2024-11-27 14:16:03 +03:00
138 lines
2.8 KiB
Go
138 lines
2.8 KiB
Go
package circuit
|
||
|
||
/*
|
||
* @Description: https://github.com/crazybber
|
||
* @Author: Edward
|
||
* @Date: 2020-05-10 22:00:58
|
||
* @Last Modified by: Edward
|
||
* @Last Modified time: 2020-05-10 22:02:18
|
||
*/
|
||
|
||
import (
|
||
"context"
|
||
"errors"
|
||
"sync"
|
||
"time"
|
||
)
|
||
|
||
////////////////////////////////
|
||
///使用HTTP请求的例子
|
||
//每个搜索引擎时时刻刻都会遇到超大规模的请求的流量.
|
||
//这里演示一个复杂一点的例子，同时使用Option 模式
|
||
|
||
//ErrServiceUnavailable for error
|
||
var (
|
||
ErrTooManyRequests = errors.New("too many requests")
|
||
ErrServiceUnavailable = errors.New("service unavailable")
|
||
FailureThreshold = 10
|
||
)
|
||
|
||
//StateCheckerHandler check state
|
||
type StateCheckerHandler func(counts counters) bool
|
||
|
||
//StateChangedEventHandler set event handle
|
||
type StateChangedEventHandler func(name string, from State, to State)
|
||
|
||
//Option set Options
|
||
type Option func(opts *Options)
|
||
|
||
//RequestBreaker for protection
|
||
type RequestBreaker struct {
|
||
options Options
|
||
mutex sync.Mutex
|
||
state State
|
||
generation uint64
|
||
counts Counter
|
||
}
|
||
|
||
//NewRequestBreaker return a breaker
|
||
func NewRequestBreaker() *RequestBreaker {
|
||
|
||
}
|
||
|
||
//State of current switch
|
||
type State int
|
||
|
||
//states of CircuitBreaker
|
||
const (
|
||
UnknownState State = iota
|
||
FailureState
|
||
SuccessState
|
||
)
|
||
|
||
//Circuit of action stream
|
||
type Circuit func(context.Context) error
|
||
|
||
//Counter interface
|
||
type Counter interface {
|
||
Count(State)
|
||
ConsecutiveFailures() uint32
|
||
LastActivity() time.Time
|
||
Reset()
|
||
}
|
||
|
||
type counters struct {
|
||
state State
|
||
lastActivity time.Time
|
||
counts uint32 //counts of failures
|
||
}
|
||
|
||
func (c *counters) Count(state State) {
|
||
|
||
}
|
||
|
||
func (c *counters) ConsecutiveFailures() uint32 {
|
||
|
||
return 0
|
||
}
|
||
|
||
func (c *counters) LastActivity() time.Time {
|
||
return c.lastActivity
|
||
}
|
||
|
||
func (c *counters) Reset() {
|
||
|
||
}
|
||
|
||
//NewCounter New Counter for Circuit Breaker
|
||
func NewCounter() Counter {
|
||
return &counters{}
|
||
}
|
||
|
||
//Breaker of circuit
|
||
func Breaker(c Circuit, failureThreshold uint32) Circuit {
|
||
|
||
cnt := NewCounter()
|
||
|
||
return func(ctx context.Context) error {
|
||
if cnt.ConsecutiveFailures() >= failureThreshold {
|
||
|
||
canRetry := func(cnt Counter) bool {
|
||
backoffLevel := cnt.ConsecutiveFailures() - failureThreshold
|
||
|
||
// Calculates when should the circuit breaker resume propagating requests
|
||
// to the service
|
||
shouldRetryAt := cnt.LastActivity().Add(time.Second * 2 << backoffLevel)
|
||
|
||
return time.Now().After(shouldRetryAt)
|
||
}
|
||
|
||
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
|
||
}
|
||
}
|
||
|
||
// Unless the failure threshold is exceeded the wrapped service mimics the
|
||
// old behavior and the difference in behavior is seen after consecutive failures
|
||
if err := c(ctx); err != nil {
|
||
cnt.Count(FailureState)
|
||
return err
|
||
}
|
||
|
||
cnt.Count(SuccessState)
|
||
return nil
|
||
}
|
||
}
|