Allows for keepalive to be called every X ms while waiting for task to complete

keepAliveProcessor.js

//reqs:
// if task takes longer the X ms to complete then send a resposne to caller and continue to process task
const delay = (ms = 500) =>
  new Promise(resolve => setTimeout(resolve, ms))

const taskA = async () => {
  await delay(1200)
  console.log('task A complete')
  return 'A'
}


const keepAliveFn = async () => {
  console.log('keep alive')
  return 'B'
}


const keepAliveProcessor = async (taskFn, keepAliveCb, timeout) => {
  const keepAliveWrapper = async () => {

    const result = await keepAliveCb()
    return { __timeout: true, result }
  }

  const taskFnWrapper = async () => {
    const result = await taskFn()
    return { __timeout: false, result }
  }

  let processingComplete = false
  const taskPromise = taskFnWrapper()
  let race
  while (!processingComplete) {
    race = await Promise.race([taskPromise, keepAliveWrapper()])
    processingComplete = race.__timeout === false
    if (!processingComplete) {
      await delay(timeout - 100)
    }
  }
  return race.result
}


keepAliveProcessor(taskA, keepAliveFn, 300)
  .then(x => console.log('fin', x))
  .catch(x => console.error(x))

//OUTPUT:
// ​​​​​keep alive​​​​​ 
// ​​​​​keep alive​​​​​ 
// ​​​​​keep alive​​​​​ 
// ​​​​​keep alive​​​​​ 
// ​​​​​keep alive​​​​​ 
// ​​​​​keep alive​​​​​ 
// ​​​​​task A complete​​​​​ 
// ​​​​​keep alive​​​​​   --- maybe an issue, haven't solved cancelling last keep alive
// ​​​​​fin A​​​​​