Node.js and CPU profiling on production (in real-time without downtime)

app.js

// Simple demo of how to integrate in app.js
const inspectorSocket = require('./sockets/inspectorSocket');
const io = require('socket.io')(server);
app.set('socketio', io);

inspectorSocket(io);

inspectorSocket.js

/**
 * Reference: Node.js and CPU profiling on production (in real-time without downtime)
 * https://medium.com/voodoo-engineering/node-js-and-cpu-profiling-on-production-in-real-time-without-downtime-d6e62af173e2
 **/

const inspector = require('inspector');
const session = new inspector.Session();
const { uploadFile2GCS } = require('./../google/storage');

session.connect();

let timer;

// 每此存檔後便開始紀錄下一次的 Profile
const saveCPUProfile = socket => {
  session.post('Profiler.stop', async (err, { profile }) => {
    if (!err) {
      // 直接將檔案上傳到 Google Cloud Storage
      const filename = `profile-${Date.now()}.cpuprofile`;
      await uploadFile2GCS({
        data: JSON.stringify(profile),
        filename,
      });

      socket.emit('message', `file uploaded - ${filename}`);

      session.post('Profiler.start');
    }
  });
};

// 開始啟動監控
const startInspect = socket => {
  socket.emit('message', 'start inspect');

  // 啟動 Profiler 並開始監控
  session.post('Profiler.enable', () => {
    session.post('Profiler.start');
  });

  // 每分鐘會進行一次寫檔
  return setInterval(() => saveCPUProfile(socket), 1 * 60 * 1000);
};

// 停止繼續監控
const stopInspect = socket => {
  socket.emit('message', 'stop inspect');
  clearInterval(timer);
  timer = null;
};

export default io => {
  // 透過 socket 來啟動或停止監控
  io.of('/inspector').on('connection', socket => {
    socket.on('message', payload => {
      const { key, msg } = payload;
      if (key !== '50868012') {
        console.log('Invalid inspector key');
        return;
      }
      switch (msg) {
        case 'startInspect': {
          if (timer) {
            socket.emit(
              'message',
              'some inspector is still running, stop it before invoke other inspector... '
            );
            return;
          }

          timer = startInspect(socket);
          break;
        }
        case 'stopInspect': {
          stopInspect(socket);
          break;
        }
        default:
          stopInspect(socket);
      }
    });

    // socket.on('disconnect', () => {
    //   stopInspect(socket);
    // });
  });
};

storage.js

import { Storage } from '@google-cloud/storage';

const storage = new Storage({
  keyFilename: '<credential>.json',
});

const BUCKET_NAME = 'jubo-demo';
const bucket = storage.bucket(BUCKET_NAME);

const uploadFile2GCS = ({ data, filename }) =>
  new Promise((resolve, reject) => {
    const file = bucket.file(filename);
    const stream = file.createWriteStream({
      contentType: 'application/octet-stream',
    });

    stream.on('error', (err) => {
      reject(err);
    });

    stream.on('finish', () => {
      resolve(`https://storage.googleapis.com/${BUCKET_NAME}/${filename}`);
    });

    stream.end(data);
  });

export { storage, uploadFile2GCS };