s3 tar streamer attempt

archiver.js

var knox = require("knox");
var mpu = require("knox-mpu");
var s3lister = require("s3-lister");
var async = require("async");
var stream = require("stream");
var tar = require("tar");

var bufferSize = 5;

var client = knox.createClient({
  key: process.env.S3_ACCESS_KEY_ID,
  secret: process.env.S3_SECRET_KEY,
  bucket: process.env.S3_BUCKET
});

var lister = new s3lister(client, { prefix: 'departments' });
var keys = [];
var tarStream = tar.Pack();

lister.on('data', function(data) {
  console.log(data.Key);
  keys.push(data.Key);
});

lister.on('end', function() {
  console.log('==> Done!, looping over keys...');
  async.mapSeries(keys, function(key) {
    client.get(key).on('response', function(res){
      console.log(res.statusCode);
      res.pipe(tarStream);
    }).end();
  }, function(results) {
    console.log(results);
  });
});

lister.on('error', function(err) {
  console.log('==> Error!', err);
});

var upload = new mpu({
  client: client,
  objectName: 'departments.tar',
  stream: tarStream
}, function(err, body) {
  console.log(body);
});

STDERR

events.js:72
        throw er; // Unhandled 'error' event
              ^
Error: write after end
    at writeAfterEnd (_stream_writable.js:133:12)
    at WriteStream.Writable.write (_stream_writable.js:181:5)
    at Pack.<anonymous> (/Users/jordan/Code/nuts.com/image-archiver/node_modules/knox-mpu/lib/multipartupload.js:246:28)
    at Pack.EventEmitter.emit (events.js:95:17)
    at EntryWriter.<anonymous> (/Users/jordan/Code/nuts.com/image-archiver/node_modules/tar/lib/pack.js:191:8)
    at EntryWriter.EventEmitter.emit (events.js:95:17)
    at BlockStream.<anonymous> (/Users/jordan/Code/nuts.com/image-archiver/node_modules/tar/lib/entry-writer.js:29:8)
    at BlockStream.EventEmitter.emit (events.js:95:17)
    at BlockStream._emitChunk (/Users/jordan/Code/nuts.com/image-archiver/node_modules/tar/node_modules/block-stream/block-stream.js:145:10)
    at BlockStream.flush (/Users/jordan/Code/nuts.com/image-archiver/node_modules/tar/node_modules/block-stream/block-stream.js:70:8)