Promise-spool NPM

promise-spool

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spool up promise based workers, feed them from a paginated api

Highlights:

install

npm i --save promise-spool

usage

let concurrency = 2
let highWaterMark = 2

// like streams, the null element at the end signifies that there's no more data
let results = [...underlyingResource].push(null)

function fetch (retrieved) {
  // retrieved will be the number of results previously retrieved by fetch
  // useful for pagination
  return vow.resolve(results.slice(retrieved, 5))
}
function worker (item, retry) {
  // item will be the next result from fetch
  // retry is a fn you can use to push an item back into the queue
  return doSomething(item)
  .catch((err) => {
    if (err.message === 'timeout') retry(item)
  }
}
promiseSpool({
  fetch, // fn returning promise which resolves to array of results
  worker, // fn returning promise which resolves when done
  concurrency, // number of concurrent workers (default: 2)
  highWaterMark // how many results to buffer from fetch (default: 2)
})
.then(() => console.log('done!'))