Streaming file from S3 with Express including information on length and filetype

Question

Using the aws-sdk module and Express 4.13, it\'s possible to proxy a file from S3 a number of ways.

This callback version will return the file body as a

Answer 1

For my project, I simply do a headObject in order to retrieve the object metadata only (it's really fast and avoid to download the object). Then I add in the response all the headers I need to propagate for the piping:

    var s3 = new AWS.S3();

    var params = {
        Bucket: bucket,
        Key: key
    };
    s3.headObject(params, function (err, data) {
        if (err) {
            // an error occurred
            console.error(err);
            return next();
        }
        var stream = s3.getObject(params).createReadStream();

        // forward errors
        stream.on('error', function error(err) {
            //continue to the next middlewares
            return next();
        });

        //Add the content type to the response (it's not propagated from the S3 SDK)
        res.set('Content-Type', mime.lookup(key));
        res.set('Content-Length', data.ContentLength);
        res.set('Last-Modified', data.LastModified);
        res.set('ETag', data.ETag);

        stream.on('end', () => {
            console.log('Served by Amazon S3: ' + key);
        });
        //Pipe the s3 object to the response
        stream.pipe(res);
    });