Use heartbeats to select a leader node.

pg-pubsub-beat.js

const PGPubsub = require("pg-pubsub");

const randInt = max => Math.floor(Math.random() * max);
const now = () => Math.floor(Date.now());
const isMyTurn = () => Math.max(...beats.map(b => b.node)) === node;

// node value
// might cause collisions,
// but let's keep it simple
const node = randInt(Number.MAX_SAFE_INTEGER);

// beats
let beats = [];

// init connection
const init = (opts = {}) => {
  const config = {
    instance: undefined,
    db: undefined,
    interval: 10000,
    ...opts
  };

  if (!config.instance && !config.db) {
    throw new Error("Please check your connection");
  }

  const pubSub = config.instance || new PGPubsub(config.db);
  // update beats
  pubSub.addChannel("beats", payload => {
    beats = beats.filter(b => b.time + config.interval * 2 > now());
    beats.push({ ...payload, time: now() });
  });

  // send beat
  const pubBeat = () => {
    pubSub.publish("beats", { node });
  };

  // send beats every
  setInterval(pubBeat, config.interval);

  // send first beat
  pubBeat();
  return pubSub;
};

module.exports = {
  init,
  isMyTurn
};