Trying to download a file from aws s3 into nodejs writeStream - node.js

Question

I am trying to download a file from s3 and directly put into into a file on the filesystem using a writeStream in nodejs. This is my code:
downloadFile = function(bucketName, fileName, localFileName) {
//Donwload the file
var bucket = new AWS.S3({
params: { Bucket: bucketName },
signatureVersion: 'v4'
});
var file = require('fs').createWriteStream(localFileName);
var request = bucket.getObject({ Key: fileName });
request.createReadStream().pipe(file);
request.send();
return request.promise();
}
Running this function I get this error:
Uncaught Error: write after end
What is happening? Is the file closed before the write is finished? Why?

Answer 1

var s3 = new AWS.S3({
accessKeyId: accessKeyId,
secretAccessKey: secretAccessKey
}),
file = fs.createWriteStream(localFileName);
s3
.getObject({
Bucket: bucketName,
Key: fileName
})
.on('error', function (err) {
console.log(err);
})
.on('httpData', function (chunk) {
file.write(chunk);
})
.on('httpDone', function () {
file.end();
})
.send();

Answer 2

Also AWS notes an example of using promises like this:
const s3 = new aws.S3({apiVersion: '2006-03-01'});
const params = { Bucket: 'yourBucket', Key: 'yourKey' };
const file = require('fs').createWriteStream('./local_file_path');
const s3Promise = s3.getObject(params).promise();
s3Promise.then((data) => {
file.write(data.Body, () => {
file.end();
fooCallbackFunction();
});
}).catch((err) => {
console.log(err);
});
This works perfect for me.
https://docs.aws.amazon.com/sdk-for-javascript/v2/developer-guide/using-promises.html
EDIT: (15 Feb 2018) Updated the code, as you have to end the write stream (file.end()).

Answer 3

I have combined the above response with a typical gunzip operation in pipe:
var s3DestFile = "./archive.gz";
var s3UnzippedFile = './deflated.csv';
var gunzip = zlib.createGunzip();
var file = fs.createWriteStream( s3DestFile );
s3.getObject({ Bucket: Bucket, Key: Key })
.on('error', function (err) {
console.log(err);
})
.on('httpData', function (chunk) {
file.write(chunk);
})
.on('httpDone', function () {
file.end();
console.log("downloaded file to" + s3DestFile);
fs.createReadStream( s3DestFile )
.on('error', console.error)
.on('end', () => {
console.log("deflated to "+s3UnzippedFile)
})
.pipe(gunzip)
.pipe(fs.createWriteStream( s3UnzippedFile ))
})
.send();