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'use strict'
const {
BalancedPoolMissingUpstreamError,
InvalidArgumentError
} = require('./core/errors')
const {
PoolBase,
kClients,
kNeedDrain,
kAddClient,
kRemoveClient,
kGetDispatcher
} = require('./pool-base')
const Pool = require('./pool')
const { kUrl, kInterceptors } = 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')
function getGreatestCommonDivisor (a, b) {
if (b === 0) return a
return getGreatestCommonDivisor(b, a % b)
}
function defaultFactory (origin, opts) {
return new Pool(origin, opts)
}
class BalancedPool extends PoolBase {
constructor (upstreams = [], { factory = defaultFactory, ...opts } = {}) {
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]
}
if (typeof factory !== 'function') {
throw new InvalidArgumentError('factory must be a function.')
}
this[kInterceptors] = opts.interceptors && opts.interceptors.BalancedPool && Array.isArray(opts.interceptors.BalancedPool)
? opts.interceptors.BalancedPool
: []
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 () {
this[kGreatestCommonDivisor] = this[kClients].map(p => p[kWeight]).reduce(getGreatestCommonDivisor, 0)
}
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
}
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
|
