how to pipe an archive (zip) to an S3 bucket

I’m a bit confused with how to proceed. I am using Archive ( node js module) as a means to write data to a zip file. Currently, I have my code working when I write to a file (local storage).

var fs = require('fs');
var archiver = require('archiver');

var output = fs.createWriteStream(__dirname + '/example.zip');
var archive = archiver('zip', {
     zlib: { level: 9 }  
});

archive.pipe(output);
archive.append(mybuffer, {name: ‘msg001.txt’});

I’d like to modify the code so that the archive target file is an AWS S3 bucket. Looking at the code examples, I can specify the bucket name and key (and body) when I create the bucket object as in:

var s3 = new AWS.S3();
var params = {Bucket: 'myBucket', Key: 'myMsgArchive.zip' Body: myStream};
s3.upload( params, function(err,data){
    … 
});

Or 

s3 = new AWS.S3({ parms: {Bucket: ‘myBucket’ Key: ‘myMsgArchive.zip’}});
s3.upload( {Body: myStream})
    .send(function(err,data) {
    …
    });

With regards to my S3 example(s), myStream appears to be a readable stream and I am confused as how to make this work as archive.pipe requires a writeable stream. Is this something where we need to use a pass-through stream? I’ve found an example where someone created a pass-through stream but the example is too terse to gain proper understanding. The specific example I am referring to is:

Pipe a stream to s3.upload()

Any help someone can give me would greatly be appreciated. Thanks.

This could be useful for anyone else wondering how to use pipe.

Since you correctly referenced the example using the pass-through stream, here's my working code:

1 - The routine itself, zipping files with node-archiver

exports.downloadFromS3AndZipToS3 = () => {
  // These are my input files I'm willing to read from S3 to ZIP them

  const files = [
    `${s3Folder}/myFile.pdf`,
    `${s3Folder}/anotherFile.xml`
  ]

  // Just in case you like to rename them as they have a different name in the final ZIP

  const fileNames = [
    'finalPDFName.pdf',
    'finalXMLName.xml'
  ]

  // Use promises to get them all

  const promises = []

  files.map((file) => {
    promises.push(s3client.getObject({
      Bucket: yourBubucket,
      Key: file
    }).promise())
  })

  // Define the ZIP target archive

  let archive = archiver('zip', {
    zlib: { level: 9 } // Sets the compression level.
  })

  // Pipe!

  archive.pipe(uploadFromStream(s3client, 'someDestinationFolderPathOnS3', 'zipFileName.zip'))

  archive.on('warning', function(err) {
    if (err.code === 'ENOENT') {
      // log warning
    } else {
      // throw error
      throw err;
    }
  })

  // Good practice to catch this error explicitly
  archive.on('error', function(err) {
    throw err;
  })

  // The actual archive is populated here 

  return Promise
    .all(promises)
    .then((data) => {
      data.map((thisFile, index) => {
        archive.append(thisFile.Body, { name: fileNames[index] })
      })

      archive.finalize()
    })
  }

2 - The helper method

const uploadFromStream = (s3client) => {
  const pass = new stream.PassThrough()

  const s3params = {
    Bucket: yourBucket,
    Key: `${someFolder}/${aFilename}`,
    Body: pass,
    ContentType: 'application/zip'
  }

  s3client.upload(s3params, (err, data) => {
    if (err)
      console.log(err)

    if (data)
      console.log('Success')
  })

  return pass
}