Nuxt js cluster mode (without PM2)

[vtonchev]

Hey, Everyone! I want to ask if somebody knows how to start Nuxt js in cluster mode without pm2 or any other process manager. I guess I have to do it programatically or writing a module, however I just can't find any information about it. I started exploring every single part of Nuxt js server, but it is not that easy, so if you know something please share it. Thank you.

[vtonchev]

Hey again, I made it. Later I am going to post my solution. Right now I am too busy chasing a deadline.

[vtonchev]

const { loadNuxt } = require('nuxt-start')
const cluster = require('cluster');

// this number of workers 
const instanses = 2

if (cluster.isMaster) {
  for (let i = 0; i < instances; i ++) {
    console.log('a')
    cluster.fork();
  }

  cluster.on("exit", (worker, code) => {
    // worker finished because of an error
    if (code !== 0 && !worker.exitedAfterDisconnect) {
      console.log("Worker crashed. Starting a new one");
      cluster.fork();
    }
  });
  
  
  //signal of workers restart (when this signal is called it performes a recursive function disconnectiong workers and adding new ones on the same place and so it is performed a zero downtime update)
  process.on("SIGUSR2", () => {
    const workers = Object.keys(cluster.workers);
    console.log("workers: ", workers);

    //recursive function over workers
    const restartWorker = workerIndex => {
      if (workerIndex >= workers.length) return;

      const worker = cluster.workers[workers[workerIndex]];
      console.log(`Stopping worker: ${worker.process.pid}`);
      worker.disconnect(); // disconnect task
      worker.on("exit", () => {
        if (!worker.exitedAfterDisconnect) return;
        // when the worker was disconnected we can start a new one
        const newWorker = cluster.fork();
        newWorker.on("listening", () => {
          // once the new worker is listerning we can restart the next worker
          restartWorker(workerIndex + 1);
        });
      });
    };

    restartWorker(0);
  });

  // Listen when a worker start listening
  cluster.on('listening', (worker, address) => {
    console.log(`A worker is now connected to ${address.address}:${address.port}`);
  });
}

// Code to run in worker process
if(cluster.isWorker) {
  // this part here is taken from the programmatic examples in the nuxt js github library
  // https://github.com/nuxt/nuxt.js/tree/dev/examples/programmatic

  const startNuxtWorker = async () => {
    const nuxt = await loadNuxt({ for: 'start' })
    await nuxt.listen(3000)
  }
  startNuxtWorker()

  
}

[vtonchev]

the whole thing is a run script you have to write this code to a .js file and save it somewhere inside your project.
After you have created such a js file you go to your package.json file and add inside scripts a new one:
"start-cluster": "node scripts/start.js"
the next time you want to start nuxt js in cluster mode you have to build is first and then type inside your terminal 'npm run start-cluster'
of course if you want to run your app in dev mode as well as in cluster mode you have to change the code inside the if statement (cluster.isWorker). The code you need is in the prgrammatic examples in the nuxt js github.

[xtoolkit]

hi
i test your solution. but nuxt error:

This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). The promise rejected with the reason:
Error: Address `0.0.0.0:3000` is already in use.
    at listenOnMasterHandle (net.js:1347:16)
    at rr (internal/cluster/child.js:126:12)
    at Worker.send (internal/cluster/child.js:93:7)
    at process.onInternalMessage (internal/cluster/utils.js:45:8)
    at process.emit (events.js:203:15)
    at processEmit [as emit] (/home/arshen/dev/gapfilm/nuxt/node_modules/signal-exit/index.js:161:32)
    at emit (internal/child_process.js:832:12)
    at process._tickCallback (internal/process/next_tick.js:63:19)