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
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
|
'use strict'
const {
BalancedPoolMissingUpstreamError,
InvalidArgumentError
} = require('../core/errors')
const {
PoolBase,
kClients,
kNeedDrain,
kAddClient,
kRemoveClient,
kGetDispatcher
} = require('./pool-base')
const Pool = require('./pool')
const { kUrl } = require('../core/symbols')
const { parseOrigin } = require('../core/util')
const kFactory = Symbol('factory')
const kOptions = Symbol('options')
const kGreatestCommonDivisor = Symbol('kGreatestCommonDivisor')
const kCurrentWeight = Symbol('kCurrentWeight')
const kIndex = Symbol('kIndex')
const kWeight = Symbol('kWeight')
const kMaxWeightPerServer = Symbol('kMaxWeightPerServer')
const kErrorPenalty = Symbol('kErrorPenalty')
/**
* Calculate the greatest common divisor of two numbers by
* using the Euclidean algorithm.
*
* @param {number} a
* @param {number} b
* @returns {number}
*/
function getGreatestCommonDivisor (a, b) {
if (a === 0) return b
while (b !== 0) {
const t = b
b = a % b
a = t
}
return a
}
function defaultFactory (origin, opts) {
return new Pool(origin, opts)
}
class BalancedPool extends PoolBase {
constructor (upstreams = [], { factory = defaultFactory, ...opts } = {}) {
if (typeof factory !== 'function') {
throw new InvalidArgumentError('factory must be a function.')
}
super()
this[kOptions] = opts
this[kIndex] = -1
this[kCurrentWeight] = 0
this[kMaxWeightPerServer] = this[kOptions].maxWeightPerServer || 100
this[kErrorPenalty] = this[kOptions].errorPenalty || 15
if (!Array.isArray(upstreams)) {
upstreams = [upstreams]
}
this[kFactory] = factory
for (const upstream of upstreams) {
this.addUpstream(upstream)
}
this._updateBalancedPoolStats()
}
addUpstream (upstream) {
const upstreamOrigin = parseOrigin(upstream).origin
if (this[kClients].find((pool) => (
pool[kUrl].origin === upstreamOrigin &&
pool.closed !== true &&
pool.destroyed !== true
))) {
return this
}
const pool = this[kFactory](upstreamOrigin, Object.assign({}, this[kOptions]))
this[kAddClient](pool)
pool.on('connect', () => {
pool[kWeight] = Math.min(this[kMaxWeightPerServer], pool[kWeight] + this[kErrorPenalty])
})
pool.on('connectionError', () => {
pool[kWeight] = Math.max(1, pool[kWeight] - this[kErrorPenalty])
this._updateBalancedPoolStats()
})
pool.on('disconnect', (...args) => {
const err = args[2]
if (err && err.code === 'UND_ERR_SOCKET') {
// decrease the weight of the pool.
pool[kWeight] = Math.max(1, pool[kWeight] - this[kErrorPenalty])
this._updateBalancedPoolStats()
}
})
for (const client of this[kClients]) {
client[kWeight] = this[kMaxWeightPerServer]
}
this._updateBalancedPoolStats()
return this
}
_updateBalancedPoolStats () {
let result = 0
for (let i = 0; i < this[kClients].length; i++) {
result = getGreatestCommonDivisor(this[kClients][i][kWeight], result)
}
this[kGreatestCommonDivisor] = result
}
removeUpstream (upstream) {
const upstreamOrigin = parseOrigin(upstream).origin
const pool = this[kClients].find((pool) => (
pool[kUrl].origin === upstreamOrigin &&
pool.closed !== true &&
pool.destroyed !== true
))
if (pool) {
this[kRemoveClient](pool)
}
return this
}
getUpstream (upstream) {
const upstreamOrigin = parseOrigin(upstream).origin
return this[kClients].find((pool) => (
pool[kUrl].origin === upstreamOrigin &&
pool.closed !== true &&
pool.destroyed !== true
))
}
get upstreams () {
return this[kClients]
.filter(dispatcher => dispatcher.closed !== true && dispatcher.destroyed !== true)
.map((p) => p[kUrl].origin)
}
[kGetDispatcher] () {
// We validate that pools is greater than 0,
// otherwise we would have to wait until an upstream
// is added, which might never happen.
if (this[kClients].length === 0) {
throw new BalancedPoolMissingUpstreamError()
}
const dispatcher = this[kClients].find(dispatcher => (
!dispatcher[kNeedDrain] &&
dispatcher.closed !== true &&
dispatcher.destroyed !== true
))
if (!dispatcher) {
return
}
const allClientsBusy = this[kClients].map(pool => pool[kNeedDrain]).reduce((a, b) => a && b, true)
if (allClientsBusy) {
return
}
let counter = 0
let maxWeightIndex = this[kClients].findIndex(pool => !pool[kNeedDrain])
while (counter++ < this[kClients].length) {
this[kIndex] = (this[kIndex] + 1) % this[kClients].length
const pool = this[kClients][this[kIndex]]
// find pool index with the largest weight
if (pool[kWeight] > this[kClients][maxWeightIndex][kWeight] && !pool[kNeedDrain]) {
maxWeightIndex = this[kIndex]
}
// decrease the current weight every `this[kClients].length`.
if (this[kIndex] === 0) {
// Set the current weight to the next lower weight.
this[kCurrentWeight] = this[kCurrentWeight] - this[kGreatestCommonDivisor]
if (this[kCurrentWeight] <= 0) {
this[kCurrentWeight] = this[kMaxWeightPerServer]
}
}
if (pool[kWeight] >= this[kCurrentWeight] && (!pool[kNeedDrain])) {
return pool
}
}
this[kCurrentWeight] = this[kClients][maxWeightIndex][kWeight]
this[kIndex] = maxWeightIndex
return this[kClients][maxWeightIndex]
}
}
module.exports = BalancedPool
|
