import cluster, { Worker } from 'cluster';
import os from 'os';
const numCPUs = os.cpus().length;

// Primary process
// This is the node that runs and controls where to distribute traffic it is slave processors
// This follows the master to slave model because the master is distribute the work hitting your server
if (cluster.isMaster) {
  console.log(`Primary ${process.pid} is in control running with ${numCPUs} threads`);

  // Fork workers.
  for (let i = 0; i < numCPUs; i++) {
    // Child processes have event listeners
    // Events: ChildProcess { _events:  { internalMessage: [Array], error: [Function], message: [Function], exit: [Object], disconnect: [Object] }, }
    // Therefore to add listeners for my master cluster I will define my listeners after they are forked
    // With the boolean flag: { isMaster: false }
    // The parameter for this function is your .env variables please clone them
    // with an import at the top of your file or passing them in for different variables for each
    cluster.fork();
  }

  // Order does not matter on these event listeners because they are the key names 
  // for child process however you can provide extra events to the master
  // These child process events tell the master how to handle their actions
  // when this events take place
  // The importance on different events on master and slaves 
  // is to have one master so EADDRINUSE does not occur floating on your EC2 (Virtual Machine)
  cluster.on('online', function (worker: Worker) {
    // Your process is healthy and ready to do work
    if (worker.process.connected) console.log('Worker ' + worker.process.pid + ' is online');
  });

  cluster.on('disconnect', (worker: Worker) => {
    // This will emit event 'exit' after this function
    console.log(`worker ${worker.process.pid} disconnected a new one will be created once it exits`);
  });

  cluster.on('exit', (worker: Worker, exitCode: number, signalCode: string) => {
    console.log(`worker ${worker.process.pid} died`);
    // Create a new child process after one has been killed
    cluster.fork();
    console.log(`worker ${worker.process.pid} is attempting to signal for a new worker to take it's place`);
  });

} else {
  // isMaster will be false
  // isWorker will be true: set the children's work
  require('./service');
}