const cluster = require('cluster');
const http = require('http');
const numCPUs = require('os').cpus().length;

if (cluster.isPrimary) {
  console.log(`Primary ${process.pid} is running`);

  // Fork initial workers
  for (let i = 0; i < numCPUs; i++) {
    cluster.fork();
  }

  // Store worker refs
  let workers = Object.values(cluster.workers);

  // Restart one worker at a time
  function restartWorker(workerIndex) {
    const worker = workers[workerIndex];
    console.log(`Restarting worker #${worker.id}`);

    // Create a new worker
    const newWorker = cluster.fork();
    
    // Add the new worker to our array
    workers.push(newWorker);
    
    // When the new worker is online, disconnect the old worker
    newWorker.on('online', () => {
      if (worker) {
        console.log(`New worker #${newWorker.id} is online, disconnecting old worker #${worker.id}`);
        worker.disconnect();
      }
    });

    // When the old worker is disconnected, remove it from the array
    worker.on('disconnect', () => {
      console.log(`Worker #${worker.id} disconnected`);
      workers = workers.filter(w => w.id !== worker.id);
    });

    // Continue the process if there are more workers to restart
    if (workerIndex + 1 < workers.length) {
      setTimeout(() => {
        restartWorker(workerIndex + 1);
      }, 5000);
    }
  }

  // Example: trigger a rolling restart after 15 seconds
  setTimeout(() => {
    console.log('Starting rolling restart of workers...');
    restartWorker(0);
  }, 15000);

  // Additional event handlers
  cluster.on('exit', (worker, code, signal) => {
    console.log(`Worker ${worker.process.pid} exited with code ${code}`);
  });

} else {
  // Worker process
  http.createServer((req, res) => {
    res.writeHead(200);
    res.end(`Hello from worker ${process.pid}, started at ${new Date().toISOString()}\n`);
  }).listen(8000);

  console.log(`Worker ${process.pid} started`);
}