-
Notifications
You must be signed in to change notification settings - Fork 795
/
weighted_round_robin.go
153 lines (134 loc) · 3.7 KB
/
weighted_round_robin.go
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
/*
* 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"
)
var (
_ Picker = &WeightedRoundRobinPicker{}
_ Picker = &RoundRobinPicker{}
)
const wrrVNodesBatchSize = 500 // it will calculate wrrVNodesBatchSize vnodes when insufficient
type wrrNode struct {
discovery.Instance
current int
}
func newWeightedRoundRobinPicker(instances []discovery.Instance) Picker {
wrrp := new(WeightedRoundRobinPicker)
wrrp.iterator = newRound()
// shuffle nodes
wrrp.size = uint64(len(instances))
wrrp.nodes = make([]*wrrNode, wrrp.size)
offset := fastrand.Uint64n(wrrp.size)
for idx := uint64(0); idx < wrrp.size; idx++ {
wrrp.nodes[idx] = &wrrNode{
Instance: instances[(idx+offset)%wrrp.size],
current: 0,
}
}
// init vnodes
totalWeight := 0
for _, node := range instances {
totalWeight += node.Weight()
}
wrrp.vcapacity = uint64(totalWeight)
wrrp.vnodes = make([]discovery.Instance, wrrp.vcapacity)
wrrp.buildVirtualWrrNodes(wrrVNodesBatchSize)
return wrrp
}
// WeightedRoundRobinPicker implement smooth weighted round-robin algorithm.
// Refer from https://github.com/phusion/nginx/commit/27e94984486058d73157038f7950a0a36ecc6e35
type WeightedRoundRobinPicker struct {
nodes []*wrrNode
size uint64
iterator *round
vsize uint64
vcapacity uint64
vnodes []discovery.Instance
vlock sync.Mutex
}
// Next implements the Picker interface.
func (wp *WeightedRoundRobinPicker) Next(ctx context.Context, request interface{}) (ins discovery.Instance) {
idx := wp.iterator.Next() % wp.vcapacity
// fast path
if wp.vnodes[idx] != nil {
return wp.vnodes[idx]
}
// slow path
wp.vlock.Lock()
defer wp.vlock.Unlock()
if wp.vnodes[idx] != nil { // other goroutine has filled the vnodes
return wp.vnodes[idx]
}
vtarget := wp.vsize + wrrVNodesBatchSize
if idx > vtarget {
vtarget = idx
}
wp.buildVirtualWrrNodes(vtarget)
return wp.vnodes[idx]
}
func (wp *WeightedRoundRobinPicker) buildVirtualWrrNodes(vtarget uint64) {
if vtarget > wp.vcapacity {
vtarget = wp.vcapacity
}
for i := wp.vsize; i < vtarget; i++ {
wp.vnodes[i] = nextWrrNode(wp.nodes).Instance
}
wp.vsize = vtarget
}
func nextWrrNode(nodes []*wrrNode) (selected *wrrNode) {
maxCurrent := 0
totalWeight := 0
for _, node := range nodes {
node.current += node.Weight()
totalWeight += node.Weight()
if selected == nil || node.current > maxCurrent {
selected = node
maxCurrent = node.current
}
}
if selected == nil {
return nil
}
selected.current -= totalWeight
return selected
}
// RoundRobinPicker .
type RoundRobinPicker struct {
size uint64
instances []discovery.Instance
iterator *round
}
func newRoundRobinPicker(instances []discovery.Instance) Picker {
size := uint64(len(instances))
return &RoundRobinPicker{
size: size,
instances: instances,
iterator: newRound(),
}
}
// Next implements the Picker interface.
func (rp *RoundRobinPicker) Next(ctx context.Context, request interface{}) (ins discovery.Instance) {
if rp.size == 0 {
return nil
}
idx := rp.iterator.Next() % rp.size
ins = rp.instances[idx]
return ins
}