Strange node.js + http + gm + s3 behavior

Question

The purpose of this node.js code block is to download an image, resize it, upload the resized image to s3, and then upload the original image to s3.

Non-Working code:

http.get(url, function onResponse(res) {
    gm(res)
    .resize(250,250)
    .stream(function(err, stdout, stderr){
        if(debug)console.log("Resized "+key+" and created "+key+"_thumb.jpg");
        if(err){
                console.log("Error resizing image. Message:",err);
        }
        else{
            var data = {
                Bucket: 'bucket-name',
                Key: key+"_thumb.jpg",
                Body: stdout,
                ACL: "public-read",
                ContentType:"image/jpeg"
            };
            s3 = new aws.S3()
            s3.upload(data, function(err, resp) {
                if(debug)console.log(resp);
            });
            s3=null;
            stdout=null;
            data=null;
        }
    });                        
    s3 = new aws.S3()
    s3.upload({Bucket:"bucket-name", Key: key+".jpg", ACL:"public-read", ContentType:"image/jpeg" ,Body: res}, function(err,data){
        if(debug)console.log(data);
        data=null;
    });
    s3=null;
    res=null;
});

The problem is that this code block does not run as expected. In the code above the thumbnail that s3 uploads is always an empty file.

However, if I remove the second s3 upload request, the thumbnails magically start uploading correctly.

Working code:

http.get(url, function onResponse(res) {
    gm(res)
    .resize(250,250)
    .stream(function(err, stdout, stderr){
        if(debug)console.log("Resized "+key+" and created "+key+"_thumb.jpg");
        if(err){
                console.log("Error resizing image. Message:",err);
        }
        else{
            var data = {
                Bucket: 'bucket-name',
                Key: key+"_thumb.jpg",
                Body: stdout,
                ACL: "public-read",
                ContentType:"image/jpeg"
            };
            s3 = new aws.S3()
            s3.upload(data, function(err, resp) {
                if(debug)console.log(resp);
            });
            s3=null;
            stdout=null;
            data=null;
        }
    });                        
    res=null;
});

Why can I upload thumbnails in the second example, but not the first?

Answer 1

I figured it out.

After a successful http.get I use the following code to create a re-usable buffer.

res.on('data', function(chunk) {
    data.push(chunk);
}).on('end', function() {
    var imgbuffer = Buffer.concat(data);
    //create thumbnail
    //s3.upload thumbnail
    //s3.upload original
});