ioredis discover newly added nodes

ioredis.js

const Redis = require('ioredis');
const _ = require('lodash');
const randomstring = require('randomstring');
const util = require('util');

let redisCluster;

async function createRedisCluster() {
  const cluster = new Redis.Cluster([{
    port: 30001,
    host: '127.0.0.1'
  }]);

  cluster.on('error', (err) => {
    console.error(err, 'Error from Redis');
  });

  cluster.on('+node', (node) => {
    console.log('new node connected')
  })

  cluster.on('-node', () => {
    console.log('node disconnected')
  })

  cluster.on('node error', () => {
    console.log('error occurs when connecting to a node')
  })

  return new Promise((resolve) => {
    cluster.once('connect', () => {
      console.log('connected to redis')
      resolve(cluster);
    });
  });
}

const TOTAL_KEYS = 120000;

function generateKeys() {
  return _.times(TOTAL_KEYS, n => {
    return `device:${randomstring.generate(20)}:${randomstring.generate(20)}`
  })
}

const CONNECTED_DEVICES_SET_KEY = 'set:connectedDevices';

async function seedRedis() {
  const keys = generateKeys();

  await Promise.all(keys.map(key => {
    return redisCluster.set(key, 'test');
  }))

  await redisCluster.sadd(CONNECTED_DEVICES_SET_KEY, keys);

  return keys;
}

async function runScript() {
  redisCluster = await createRedisCluster();

  console.log('seeding redis')

  await seedRedis();

  setInterval(async () => {
    var masters = redisCluster.nodes('master');
    await Promise.all(masters.map(function (node) {
      return node.keys('*');
    })).then(function (keys) {
      console.log('keys: ', _.reduce(keys, (length, key) => length + key.length, 0));
    });
  }, 5000)
}

runScript().then(() => {
  console.log('done!')
}).catch(err => {

  if (redisCluster) {
    redisCluster.quit()
  }
  return console.error(`Error during running of script: ${util.inspect(err)}`)
})