experimental-sample4.js

'use strict';
const {
  performance,
  PerformanceObserver
} = require('perf_hooks');
const async_hooks = require("async_hooks")

const request = require("request")

const map = new Map()

//Creating the async hook here to piggyback on async calls
const hook = async_hooks.createHook({
  init(id, type, triggerID, resource) {
    if (type == 'GETADDRINFOREQWRAP') {
        if(!firstMark) firstMark = resource.hostname + "-Init"
          performance.mark(resource.hostname + '-Init');
      map.set(id, resource.hostname)
    }
  },
  destroy(id) {

    if (map.has(id)) {
          let host = map.get(id)
      map.delete(id);
      performance.mark(host +"-After")
      performance.measure(host,
                          host + "-Init",
                          host + "-After")
    }
  }
});
hook.enable();


//Original code starts chere
function queryEngines(done) {
    const urls = [
        "http://www.google.com",
        "http://yahoo.com",
        "http://bing.com",
        "http://duckduckgo.com"
    ]

    let results = []

    urls.forEach( (url) => {
        request(url, (err, cnt) => {
            results.push(cnt)
            if(results.length === urls.length) {
                return done(results)
            }
        })
    })
}


//The performance observer is not changed
const obs = new PerformanceObserver((list) => {
  const entry = list.getEntries()[0]
  console.log(`Time for ('${entry.name}')`, entry.duration);
});
obs.observe({ entryTypes: ['measure'], buffered: false});

queryEngines( (pages) => {
    console.log("Done!")
})