How does monitoring the event loop works?

[goldbergyoni]

Thanks for the great work. I'm just curious, where/how is the event loop monitoring happens? couldn't find that in the code, any reference will be appreciated

[vicanso]

@i0natan In the performance function, there is a setInterval.

function performance() {
  /* eslint prefer-rest-params: 0 */
  const args = Array.from(arguments);
  const interval = get(args, isNumber, 100);
  const fn = get(args, isFunction, noop);
  const unitInfo = convertUnit(get(args, isString, 'B').toUpperCase());
  let start = process.hrtime();
  let cpuUsage = process.cpuUsage && process.cpuUsage();
  const timer = setInterval(() => {
    let result = {
      lag: getDelay(start, interval),
      heap: getHeapStatistics(unitInfo),
      memoryUsage: getMemoryUsage(unitInfo),
    };
....

[goldbergyoni]

got it, so you assume that a basic interval tells the status of the loop? Node prioritize io based operations, so in theory, it can process many io based items from the queue efficiently but the items in the timers (interval) queues will get delayed (which not necessarily imply a problem)

[vicanso]

Yes, if the applcation is too busy, the performance function will be delayed.