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1'use strict'2 3const {4  PoolBase,5  kClients,6  kNeedDrain,7  kAddClient,8  kGetDispatcher,9  kRemoveClient10} = require('./pool-base')11const Client = require('./client')12const {13  InvalidArgumentError14} = require('../core/errors')15const util = require('../core/util')16const { kUrl } = require('../core/symbols')17const buildConnector = require('../core/connect')18 19const kOptions = Symbol('options')20const kConnections = Symbol('connections')21const kFactory = Symbol('factory')22const kIndex = Symbol('index')23 24function defaultFactory (origin, opts) {25  return new Client(origin, opts)26}27 28class RoundRobinPool extends PoolBase {29  constructor (origin, {30    connections,31    factory = defaultFactory,32    connect,33    connectTimeout,34    tls,35    maxCachedSessions,36    socketPath,37    autoSelectFamily,38    autoSelectFamilyAttemptTimeout,39    allowH2,40    clientTtl,41    ...options42  } = {}) {43    if (connections != null && (!Number.isFinite(connections) || connections < 0)) {44      throw new InvalidArgumentError('invalid connections')45    }46 47    if (typeof factory !== 'function') {48      throw new InvalidArgumentError('factory must be a function.')49    }50 51    if (connect != null && typeof connect !== 'function' && typeof connect !== 'object') {52      throw new InvalidArgumentError('connect must be a function or an object')53    }54 55    if (typeof connect !== 'function') {56      connect = buildConnector({57        ...tls,58        maxCachedSessions,59        allowH2,60        socketPath,61        timeout: connectTimeout,62        ...(typeof autoSelectFamily === 'boolean' ? { autoSelectFamily, autoSelectFamilyAttemptTimeout } : undefined),63        ...connect64      })65    }66 67    super()68 69    this[kConnections] = connections || null70    this[kUrl] = util.parseOrigin(origin)71    this[kOptions] = { ...util.deepClone(options), connect, allowH2, clientTtl, socketPath }72    this[kOptions].interceptors = options.interceptors73      ? { ...options.interceptors }74      : undefined75    this[kFactory] = factory76    this[kIndex] = -177 78    this.on('connect', (origin, targets) => {79      if (clientTtl != null && clientTtl > 0) {80        for (const target of targets) {81          Object.assign(target, { ttl: Date.now() })82        }83      }84    })85 86    this.on('connectionError', (origin, targets, error) => {87      for (const target of targets) {88        const idx = this[kClients].indexOf(target)89        if (idx !== -1) {90          this[kClients].splice(idx, 1)91        }92      }93    })94  }95 96  [kGetDispatcher] () {97    const clientTtlOption = this[kOptions].clientTtl98    const clientsLength = this[kClients].length99 100    // If we have no clients yet, create one101    if (clientsLength === 0) {102      const dispatcher = this[kFactory](this[kUrl], this[kOptions])103      this[kAddClient](dispatcher)104      return dispatcher105    }106 107    // Round-robin through existing clients108    let checked = 0109    while (checked < clientsLength) {110      this[kIndex] = (this[kIndex] + 1) % clientsLength111      const client = this[kClients][this[kIndex]]112 113      // Check if client is stale (TTL expired)114      if (clientTtlOption != null && clientTtlOption > 0 && client.ttl && ((Date.now() - client.ttl) > clientTtlOption)) {115        this[kRemoveClient](client)116        checked++117        continue118      }119 120      // Return client if it's not draining121      if (!client[kNeedDrain]) {122        return client123      }124 125      checked++126    }127 128    // All clients are busy, create a new one if we haven't reached the limit129    if (!this[kConnections] || clientsLength < this[kConnections]) {130      const dispatcher = this[kFactory](this[kUrl], this[kOptions])131      this[kAddClient](dispatcher)132      return dispatcher133    }134  }135}136 137module.exports = RoundRobinPool138