shortid-extend/lib/util/cluster-worker-id.js

Alternative versión with options from Dylan Greene ShortId

'use strict';

var cluster = require('cluster');

var clusterId = 0;
if (!cluster.isMaster && cluster.worker) {
    clusterId = cluster.worker.id;
}
module.exports = parseInt(process.env.NODE_UNIQUE_ID || clusterId, 10);