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weighted_balancer.go
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/
weighted_balancer.go
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/*
* Copyright 2023 CloudWeGo 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 loadbalance
import (
"sync"
"golang.org/x/sync/singleflight"
"github.com/cloudwego/kitex/pkg/discovery"
"github.com/cloudwego/kitex/pkg/klog"
)
const (
lbKindRoundRobin = iota
lbKindInterleaved
lbKindRandom
)
type weightedBalancer struct {
kind int
pickerCache sync.Map
sfg singleflight.Group
}
// NewWeightedBalancer creates a loadbalancer using weighted-round-robin algorithm.
func NewWeightedBalancer() Loadbalancer {
return NewWeightedRoundRobinBalancer()
}
// NewWeightedRoundRobinBalancer creates a loadbalancer using weighted-round-robin algorithm.
func NewWeightedRoundRobinBalancer() Loadbalancer {
lb := &weightedBalancer{kind: lbKindRoundRobin}
return lb
}
// NewInterleavedWeightedRoundRobinBalancer creates a loadbalancer using interleaved-weighted-round-robin algorithm.
func NewInterleavedWeightedRoundRobinBalancer() Loadbalancer {
lb := &weightedBalancer{kind: lbKindInterleaved}
return lb
}
// NewWeightedRandomBalancer creates a loadbalancer using weighted-random algorithm.
func NewWeightedRandomBalancer() Loadbalancer {
lb := &weightedBalancer{kind: lbKindRandom}
return lb
}
// GetPicker implements the Loadbalancer interface.
func (wb *weightedBalancer) GetPicker(e discovery.Result) Picker {
if !e.Cacheable {
picker := wb.createPicker(e)
return picker
}
picker, ok := wb.pickerCache.Load(e.CacheKey)
if !ok {
picker, _, _ = wb.sfg.Do(e.CacheKey, func() (interface{}, error) {
p := wb.createPicker(e)
wb.pickerCache.Store(e.CacheKey, p)
return p, nil
})
}
return picker.(Picker)
}
func (wb *weightedBalancer) createPicker(e discovery.Result) (picker Picker) {
instances := make([]discovery.Instance, len(e.Instances)) // removed zero weight instances
weightSum := 0
balance := true
cnt := 0
for idx, instance := range e.Instances {
weight := instance.Weight()
if weight <= 0 {
klog.Warnf("KITEX: invalid weight, weight=%d instance=%s", weight, e.Instances[idx].Address())
continue
}
weightSum += weight
instances[cnt] = instance
if cnt > 0 && instances[cnt-1].Weight() != weight {
balance = false
}
cnt++
}
instances = instances[:cnt]
if len(instances) == 0 {
return new(DummyPicker)
}
switch wb.kind {
case lbKindRoundRobin:
if balance {
picker = newRoundRobinPicker(instances)
} else {
picker = newWeightedRoundRobinPicker(instances)
}
case lbKindInterleaved:
if balance {
picker = newRoundRobinPicker(instances)
} else {
picker = newInterleavedWeightedRoundRobinPicker(instances)
}
default: // random
if balance {
picker = newRandomPicker(instances)
} else {
picker = newWeightedRandomPickerWithSum(instances, weightSum)
}
}
return picker
}
// Rebalance implements the Rebalancer interface.
func (wb *weightedBalancer) Rebalance(change discovery.Change) {
if !change.Result.Cacheable {
return
}
wb.pickerCache.Store(change.Result.CacheKey, wb.createPicker(change.Result))
}
// Delete implements the Rebalancer interface.
func (wb *weightedBalancer) Delete(change discovery.Change) {
if !change.Result.Cacheable {
return
}
wb.pickerCache.Delete(change.Result.CacheKey)
}
func (wb *weightedBalancer) Name() string {
switch wb.kind {
case lbKindRoundRobin:
return "weight_round_robin"
case lbKindInterleaved:
return "interleaved_weighted_round_robin"
default:
return "weight_random"
}
}