handler.js

const aws = require('aws-sdk')
const s3 = new aws.S3()
const path = require('path')

const outputBucket = process.env.OUTPUT_BUCKET

exports.replicate = function main(event, context) {
  // Fail on mising data
  if (!outputBucket) {
    context.fail('Error: Environment variable OUTPUT_BUCKET missing')
    return
  }
  if (event.Records === null) {
    context.fail('Error: Event has no records.')
    return
  }

  let tasks = []
  for (let i = 0; i < event.Records.length; i++) {
    tasks.push(replicatePromise(event.Records[i], outputBucket))
  }

  Promise.all(tasks)
    .then(() => { context.succeed() })
    .catch(() => { context.fail() })
}

function replicatePromise(record, destBucket) {
  return new Promise((resolve, reject) => {
    // The source bucket and source key are part of the event data
    var srcBucket = record.s3.bucket.name
    var srcKey = decodeURIComponent(record.s3.object.key.replace(/\+/g, " "))

    // Modify destKey if an alternate copy location is preferred
    var destKey = srcKey
    var msg = 'copying ' + srcBucket + ':' + srcKey + ' to ' + destBucket + ':' + destKey

    console.log('Attempting: ' + msg)
    s3.copyObject({
      Bucket: destBucket,
      Key: destKey,
      CopySource: encodeURIComponent(srcBucket + '/' + srcKey),
      MetadataDirective: 'COPY'
    }, (err, data) => {
      if (err) {
        console.log('Error:' + msg)
        console.log(err, err.stack) // an error occurred
        return reject('Error:' + msg)
      } else {
        console.log('Success: ' + msg)
        return resolve('Success: ' + msg)
      }
    })
  })
}