Getting s3 object metadata then creating stream

Question

I'm downloading an object from s3 and creating a read stream object from it to process a video:

s3.getObject(params).createReadStream()

However, I need to get the metadata from it which is possible when i just get the object by accessing its 'metadata' property:

s3.getObject()

How would I either:

1. Get the object via s3.getObject(), grab the metadata from its metadata property, and then turn it into a read stream?

   var stream = fs.createReadStream(response); isn't working - input must be a string

-- OR --

2. Get the stream via s3.getObject().createReadStream(), and extract the metadata from the stream?

   To my knowledge metadata isn't passed within streams.

---

Tell me if my assumptions are wrong, but I am currently stuck with these two needs:

• Getting the meta data
• Making it a stream

Answer 1

You can get the metadata via the request's httpHeaders event.

let fs = require('fs')
let aws = require('aws-sdk')
let s3 = new aws.S3()

let request = s3.getObject({
    Bucket: 'my-bucket',
    Key: 'my-key'
})

let stream

request.on('httpHeaders', (statusCode, httpHeaders) => {
    // object metadata is represented by any header in httpHeaders starting with 'x-amz-meta-'
    // you can use the stream object that this point
    stream.pipe(fs.createWriteStream('./somepath'))
    stream.on('end', () => { 
        console.log('were done')
    })
})

stream = request.createReadStream()

Alternatively you can also call s3.headObject to get the metadata without downloading the object and then download the object using s3.getObject