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100 lines
2.2 KiB
100 lines
2.2 KiB
package breaker
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import (
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"math"
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"math/rand"
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"sync"
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"sync/atomic"
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"time"
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"github.com/go-kratos/kratos/pkg/ecode"
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"github.com/go-kratos/kratos/pkg/log"
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"github.com/go-kratos/kratos/pkg/stat/metric"
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)
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// sreBreaker is a sre CircuitBreaker pattern.
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type sreBreaker struct {
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stat metric.RollingCounter
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r *rand.Rand
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// rand.New(...) returns a non thread safe object
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randLock sync.Mutex
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k float64
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request int64
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state int32
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}
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func newSRE(c *Config) Breaker {
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counterOpts := metric.RollingCounterOpts{
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Size: c.Bucket,
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BucketDuration: time.Duration(int64(c.Window) / int64(c.Bucket)),
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}
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stat := metric.NewRollingCounter(counterOpts)
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return &sreBreaker{
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stat: stat,
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r: rand.New(rand.NewSource(time.Now().UnixNano())),
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request: c.Request,
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k: c.K,
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state: StateClosed,
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}
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}
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func (b *sreBreaker) summary() (success int64, total int64) {
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b.stat.Reduce(func(iterator metric.Iterator) float64 {
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for iterator.Next() {
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bucket := iterator.Bucket()
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total += bucket.Count
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for _, p := range bucket.Points {
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success += int64(p)
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}
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}
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return 0
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})
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return
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}
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func (b *sreBreaker) Allow() error {
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success, total := b.summary()
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k := b.k * float64(success)
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if log.V(5) {
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log.Info("breaker: request: %d, succee: %d, fail: %d", total, success, total-success)
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}
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// check overflow requests = K * success
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if total < b.request || float64(total) < k {
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if atomic.LoadInt32(&b.state) == StateOpen {
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atomic.CompareAndSwapInt32(&b.state, StateOpen, StateClosed)
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}
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return nil
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}
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if atomic.LoadInt32(&b.state) == StateClosed {
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atomic.CompareAndSwapInt32(&b.state, StateClosed, StateOpen)
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}
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dr := math.Max(0, (float64(total)-k)/float64(total+1))
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drop := b.trueOnProba(dr)
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if log.V(5) {
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log.Info("breaker: drop ratio: %f, drop: %t", dr, drop)
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}
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if drop {
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return ecode.ServiceUnavailable
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}
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return nil
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}
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func (b *sreBreaker) MarkSuccess() {
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b.stat.Add(1)
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}
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func (b *sreBreaker) MarkFailed() {
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// NOTE: when client reject requets locally, continue add counter let the
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// drop ratio higher.
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b.stat.Add(0)
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}
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func (b *sreBreaker) trueOnProba(proba float64) (truth bool) {
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b.randLock.Lock()
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truth = b.r.Float64() < proba
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b.randLock.Unlock()
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return
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}
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