Downloads a File from a Bucket, saves it to a location on disk and returns a Promise

downloadS3Object.js

'use strict';

const fs = require('fs');
const AWS = require('aws-sdk');
const S3 = new AWS.S3(); // pass in config if you need to, use default credentials location

module.exports = (bucket, key, dest) => {
  return new Promise((resolve, reject) => {    
    let ws = fs.createWriteStream(dest);

    ws.once('error', (err) => {
      return reject(err);
    });
    
    ws.once('finish', () => {
      console.log(`File Downloaded! ${dest}`);
      return resolve(dest);
    });
    
    let s3Stream = S3.getObject({
      Bucket: bucket,
      Key: key
    }).createReadStream();
    
    // Under load this will prevent first few bytes from being lost
    s3Stream.pause()  
    
    s3Stream.on('error', (err) => {
      return reject(err);
    });
    
    s3Stream.pipe(ws);
    s3Stream.resume();
  });
};