Method connect

packages/pg-pool/index.js:190–238

(cb)

  }

  connect(cb) {
    if (this.ending) {
      const err = new Error('Cannot use a pool after calling end on the pool')
      return cb ? cb(err) : this.Promise.reject(err)
    }

    const response = promisify(this.Promise, cb)
    const result = response.result

    // if we don't have to connect a new client, don't do so
    if (this._isFull() || this._idle.length) {
      // if we have idle clients schedule a pulse immediately
      if (this._idle.length) {
        process.nextTick(() => this._pulseQueue())
      }

      if (!this.options.connectionTimeoutMillis) {
        this._pendingQueue.push(new PendingItem(response.callback))
        return result
      }

      const queueCallback = (err, res, done) => {
        clearTimeout(tid)
        response.callback(err, res, done)
      }

      const pendingItem = new PendingItem(queueCallback)

      // set connection timeout on checking out an existing client
      const tid = setTimeout(() => {
        // remove the callback from pending waiters because
        // we're going to call it with a timeout error
        removeWhere(this._pendingQueue, (i) => i.callback === queueCallback)
        pendingItem.timedOut = true
        response.callback(new Error('timeout exceeded when trying to connect'))
      }, this.options.connectionTimeoutMillis)

      if (tid.unref) {
        tid.unref()
      }

      this._pendingQueue.push(pendingItem)
      return result
    }

    this.newClient(new PendingItem(response.callback))

    return result
  }

  newClient(pendingItem) {
    const client = new this.Client(this.options)