const throng = require('throng')

throng(id => console.log(`Started worker ${id}`))

throng(workerStartFunction)

throng({ worker: workerStartFunction, count: 3 })

throng({
  master: masterStartFunction,
  worker: workerStartFunction,
  count: 16,
  grace: 1000
})

throng({ worker })

function worker(id, disconnect) {
  console.log(`Started worker ${id}`)

  process.on('SIGTERM', () => {
    console.log(`Worker ${id} exiting (cleanup here)`)
    disconnect()
  })
})

throng({
  master: () => {},               // Fn to call in master process (can be async)
  worker: yourWorkerFunc,         // Fn to call in cluster workers (can be async)
  count: os.cpus().length,        // Number of workers
  lifetime: Infinity,             // Min time to keep cluster alive (ms)
  grace: 5000,                    // Grace period between signal and hard shutdown (ms)
  signals: ['SIGTERM', 'SIGINT']  // Signals that trigger a shutdown (proxied to workers)
})

const throng = require('throng')

throng({ master, worker, count: 4 })

// This will only be called once
function master() {
  console.log('Started master')

  process.on('beforeExit', () => {
    console.log('Master cleanup.')
  })
}

// This will be called four times
function worker(id, disconnect) {
  let exited = false

  console.log(`Started worker ${ id }`)
  process.on('SIGTERM', shutdown)
  process.on('SIGINT', shutdown)

  async function shutdown() {
    if (exited) return
    exited = true

    await new Promise(r => setTimeout(r, 300))  // simulate async cleanup work
    console.log(`Worker ${ id } cleanup done.`)
    disconnect()
  }
}