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interleaved_weighted_round_robin.go
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/
interleaved_weighted_round_robin.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 (
"context"
"sync"
"github.com/bytedance/gopkg/lang/fastrand"
"github.com/cloudwego/kitex/pkg/discovery"
)
type iwrrNode struct {
discovery.Instance
remainder int
next *iwrrNode
}
type iwrrQueue struct {
head *iwrrNode
tail *iwrrNode
}
type InterleavedWeightedRoundRobinPicker struct {
current *iwrrQueue
next *iwrrQueue
gcd int
lock sync.Mutex
}
func newInterleavedWeightedRoundRobinPicker(instances []discovery.Instance) Picker {
iwrrp := new(InterleavedWeightedRoundRobinPicker)
iwrrp.current = newIwrrQueue()
iwrrp.next = newIwrrQueue()
size := uint64(len(instances))
offset := fastrand.Uint64n(size)
gcd := 0
for idx := uint64(0); idx < size; idx++ {
ins := instances[(idx+offset)%size]
gcd = gcdInt(gcd, ins.Weight())
iwrrp.current.enqueue(&iwrrNode{
Instance: ins,
remainder: ins.Weight(),
})
}
iwrrp.gcd = gcd
return iwrrp
}
func (ip *InterleavedWeightedRoundRobinPicker) Next(ctx context.Context, request interface{}) discovery.Instance {
ip.lock.Lock()
defer ip.lock.Unlock()
if ip.current.empty() {
ip.current, ip.next = ip.next, ip.current
}
node := ip.current.dequeue()
node.remainder -= ip.gcd
if node.remainder > 0 {
ip.current.enqueue(node)
} else {
node.remainder = node.Instance.Weight()
ip.next.enqueue(node)
}
return node.Instance
}
func newIwrrQueue() *iwrrQueue {
return &iwrrQueue{}
}
func (q *iwrrQueue) enqueue(node *iwrrNode) {
node.next = nil
tail := q.tail
q.tail = node
if tail == nil {
q.head = node
} else {
tail.next = node
}
}
func (q *iwrrQueue) dequeue() *iwrrNode {
head := q.head
next := head.next
head.next = nil
q.head = next
if next == nil {
q.tail = nil
}
return head
}
func (q *iwrrQueue) empty() bool {
return q.head == nil
}