Monitor aync resources in node.js application

async_reservations.js

import asyncHooks from 'async_hooks';

const reservations = new Map();
asyncHooks.createHook({
  init: function init(asyncId, type, triggerAsyncId) {
    const e = {};
    Error.captureStackTrace(e, init);
    reservations.set(asyncId, {type, triggerAsyncId, stack: e.stack});
  },
  destroy: function destroy(asyncId) {
    reservations.delete(asyncId);
  }
}).enable();

const resources = () => {
  const entries = new Map();
  const root = ['process(1)'];
  entries.set(1, root);
  for (const [asyncId, {type, triggerAsyncId, stack}] of reservations.entries()) {
    let parent = entries.get(triggerAsyncId);
    if (!parent) {
      parent = [`unknown(${triggerAsyncId})`];
      entries.set(triggerAsyncId, parent);
      root.push(parent);
    }

    const node = [`${type}(${asyncId})`, stack];
    entries.set(asyncId, node);
    parent.push(node);
  }
  return root;
};