Profile node with child processes

profile.js

/* eslint-env node */
const { Session } = require('inspector');
const fs = require('fs');

const captureExit = require('capture-exit');

captureExit.captureExit();

/** @param exitPromise {Promise<void>} */
async function runProfile(exitPromise) {
  const session = new Session();

  const waitingForDisconnect = new Promise(resolve => {
    session.once('NodeRuntime.waitingForDisconnect', resolve);
  });

  session.connect();

  await new Promise((resolve, reject) => {
    session.post(
      'NodeRuntime.notifyWhenWaitingForDisconnect',
      {
        enabled: true,
      },
      err => {
        if (err) reject(err);
        else resolve();
      }
    );
  });

  await new Promise((resolve, reject) => {
    session.post('Profiler.enable', { enabled: true }, err => {
      if (err) reject(err);
      else resolve();
    });
  });

  console.log(`STARTING PROFILE IN ${process.pid}`);

  await new Promise((resolve, reject) => {
    session.post('Profiler.start', err => {
      if (err) reject(err);
      else resolve();
    });
  });

  console.log(`PROFILE STARTED ${process.pid}`);

  await Promise.race([waitingForDisconnect, exitPromise]);

  console.log(`WAITING FOR DISCONNECT ${process.pid}`);

  const profile = await new Promise((resolve, reject) => {
    session.post('Profiler.stop', (err, { profile }) => {
      if (err) reject(err);
      else resolve(profile);
    });
  });

  console.log(`PROFILE STOPPED ${process.pid}`);
  fs.writeFileSync(`${__dirname}/${process.pid}.cpuprofile`, JSON.stringify(profile));

  session.disconnect();
}

const profilePromise = runProfile(
  new Promise(resolve => {
    captureExit.onExit(async () => {
      resolve();
      await profilePromise;
    });
  })
);

start_build_profile.sh

NODE_OPTIONS="-r $(pwd)/profile.js" ember build