untarring files to S3 fails, not sure why

Question

(new information below) I am trying to set up a lambda function that reacts to uploaded tgz files by uncompressing them and writing the results back to S3. The unzip and untar work fine, but uploading to S3 fails:

/Users/russell/lambda/gzip/node_modules/aws-sdk/lib/s3/managed_upload.js:350
    var buf = self.body.read(self.partSize - self.partBuffer.length) ||
                        ^
TypeError: undefined is not a function
    at ManagedUpload.fillStream (/Users/russell/lambda/gzip/node_modules/aws-sdk/lib/s3/managed_upload.js:350:25)
    at Entry.<anonymous> (/Users/russell/lambda/gzip/node_modules/aws-sdk/lib/s3/managed_upload.js:167:28)
    at Entry.emit (events.js:104:17)
    at Entry._read (/Users/russell/lambda/gzip/node_modules/tar/lib/entry.js:123:12)
    at Entry.end (/Users/russell/lambda/gzip/node_modules/tar/lib/entry.js:82:8)
    at Parse._process (/Users/russell/lambda/gzip/node_modules/tar/lib/parse.js:107:13)
    at BlockStream.<anonymous> (/Users/russell/lambda/gzip/node_modules/tar/lib/parse.js:47:8)
    at BlockStream.emit (events.js:107:17)
    at BlockStream._emitChunk (/Users/russell/lambda/gzip/node_modules/tar/node_modules/block-stream/block-stream.js:145:10)
    at BlockStream.write (/Users/russell/lambda/gzip/node_modules/tar/node_modules/block-stream/block-stream.js:45:10)

This error occurs when I write to S3, but if instead I write the files locally to disk it works, so the pipeline is correct.

Here is code that demonstrates the problem:

var aws = require('aws-sdk');
var s3 = new aws.S3({apiVersion: '2006-03-01'});
var zlib = require('zlib');
var tar = require('tar');
var fstream = require('fstream');

fstream.Reader({'path': 'testdata.tar.gz'})
    .pipe(zlib.Unzip())
    .pipe(tar.Parse())
    .on('entry', function(entry) {
        var filename = entry.path;
        console.log('got ' + entry.type + ' ' + filename);
        if (entry.type == 'File') {
            if (1) { // switch between working and nonworking cases
                s3.upload({Bucket: 'my_bucket', Key: 'gunzip-test/' + filename, Body: entry}, {},
                          function(err, data) {
                              if (err) 
                                  console.log('ERROR!');
                              else
                                  console.log('OK');
                          });
            }
            else {
                entry.pipe(fstream.Writer({ 'path': '/tmp/mytest/' + filename }));
            }
        }
    });

If the code is set to write to S3 it fails with the above error, if it writes the extracted files locally it succeeds. ENTRY is a stream, and according to the doc should be accepted in the upload Body parameter. I put a print statement in ManagedUpload, where the fail comes, and confirmed that self.body is a stream:

var stream = require('stream');
console.log('is it a stream? ' + ((self.body instanceof stream) ? 'yes' : 'no'));
console.log('self.body.read is ' + self.body.read);

returns

$ got File gunzip.js
is it a stream? yes
self.body.read is undefined

I'm pretty new with aws and node.js, so there could be a basic problem with this, but I've spent a day and haven't found it. I did the upload call with unzip instead of gzip and it worked (using lambda functions to unzip archives in S3 is really sloooooow) Can anyone point me at something I am doing wrong in this code?

Thanks

---

I think I understand this a little better. I broke the pipeline up into pieces and looked at each one. The problem is that tar.Parse uses fstream and not stream. If I look at the return of the .pipe(tar.Parse()) statement it is a stream, but it is not a stream.Readable or a stream.Writable. fstream does not define a read() method (its reader is based on Stream, it is not a stream.Readable), so tar.Parse, which is based on Stream, does not have one either.

So a refinement of the question is, is this a bug in fstream, or is fstream not intended to be a stream? I think it is a bug - from the README:

"Like FS streams, but with stat on them, and supporting directories and symbolic links, as well as normal files. Also, you can use this to set the stats on a file, even if you don't change its contents, or to create a symlink, etc."

Answer 1

In my case running the stream through stream.PassThrough helped.

var PassThrough = require('stream').PassThrough;

var stream = getStreamSomeHow();
var passthrough = new PassThrough();

stream.pipe(passthrough);

s3.upload({...,Body:passthrough}) // 

Answer 2

Your body variable is a Stream object, in which case you will need to use .toString()

var aws = require('aws-sdk');
var s3 = new aws.S3({apiVersion: '2006-03-01'});
var zlib = require('zlib');
var tar = require('tar');
var fstream = require('fstream');

fstream.Reader({'path': 'testdata.tar.gz'})
    .pipe(zlib.Unzip())
    .pipe(tar.Parse())
    .on('entry', function(entry) {
        var filename = entry.path;
        console.log('got ' + entry.type + ' ' + filename);
        if (entry.type == 'File') {
            if (1) { // switch between working and nonworking cases
                s3.upload({Bucket: 'my_bucket', Key: 'gunzip-test/' + filename, Body: entry.toString()}, {},
                          function(err, data) {
                              if (err) 
                                  console.log('ERROR!');
                              else
                                  console.log('OK');
                          });
            }
            else {
                entry.pipe(fstream.Writer({ 'path': '/tmp/mytest/' + filename }));
            }
        }
    });