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googlesrebreaker.go
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googlesrebreaker.go
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/*
*
* Copyright 2020 waterdrop authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
*/
package breaker
import (
"math"
"sync/atomic"
"time"
"github.com/UnderTreeTech/waterdrop/pkg/log"
"github.com/UnderTreeTech/waterdrop/pkg/status"
"github.com/UnderTreeTech/waterdrop/pkg/utils/xcollection"
)
type googleSreBreaker struct {
// k google accepts multiplier K
k float64
// state service status
state int32
// rw rolling window to stat metrics
rw *xcollection.RollingWindow
// proba open breaker probability
proba *Proba
// name breaker name
name string
}
type GoogleSreBreakerConfig struct {
K float64
Window time.Duration
BucketSize int
Name string
}
// defaultGoogleSreBreakerConfig default google sre breaker config
func defaultGoogleSreBreakerConfig() *GoogleSreBreakerConfig {
return &GoogleSreBreakerConfig{
K: 1.5,
Window: 10 * time.Second,
BucketSize: 40,
}
}
// newGoogleSreBreaker new a google sre breaker
func newGoogleSreBreaker(config *GoogleSreBreakerConfig) *googleSreBreaker {
if config == nil {
config = defaultGoogleSreBreakerConfig()
}
interval := time.Duration(int64(config.Window) / int64(config.BucketSize))
rw := xcollection.NewRollingWindow(config.BucketSize, interval)
breaker := &googleSreBreaker{
k: config.K,
rw: rw,
proba: NewProba(),
state: StateOpen,
name: config.Name,
}
return breaker
}
// Allow check the if the request can be successfully execute
func (gsb *googleSreBreaker) Allow() error {
success, total := gsb.summary()
googleAccepts := gsb.k * success
dropRatio := math.Max(0, (float64(total)-googleAccepts)/float64(total+1))
log.Debugf("breaker", log.String("name", gsb.name), log.Int64("total", total), log.Float64("success", success), log.Float64("accepts", googleAccepts), log.Float64("ratio", dropRatio))
if dropRatio <= 0 {
if atomic.LoadInt32(&gsb.state) == StateOpen {
atomic.CompareAndSwapInt32(&gsb.state, StateOpen, StateClosed)
}
return nil
}
if atomic.LoadInt32(&gsb.state) == StateClosed {
atomic.CompareAndSwapInt32(&gsb.state, StateClosed, StateOpen)
}
if gsb.proba.TrueOnProba(dropRatio) {
return status.ServiceUnavailable
}
return nil
}
// summary summarize the buckets data
func (gsb *googleSreBreaker) summary() (success float64, total int64) {
gsb.rw.Reduce(func(bucket *xcollection.Bucket) {
success += bucket.Sum
total += bucket.Count
})
return
}
// Accept indicate request execute successfully
func (gsb *googleSreBreaker) Accept() {
gsb.rw.Add(1)
}
// Reject indicate request is denied
func (gsb *googleSreBreaker) Reject() {
gsb.rw.Add(0)
}