Google Drive Api v3 get download progress - node.js

Question

I am trying to get a download progress % for a huge file stored in my Google Drive unit when downloading from my Nodejs script.
So far I have written the code to download, which is working, however the on('data'....) part is never called.
const downloadFile = (file) => {
const fileId = file.id;
const fileName = path.join(basePathForStorage, file.name);
const drive = google.drive({ version: 'v3', authorization });
let progress = 0;
return new Promise((resolve, reject) => {
drive.files.get(
{
auth: authorization,
fileId: fileId,
alt: 'media'
},
{ responseType: "arraybuffer" },
function (err, { data }) {
fs.writeFile(fileName, Buffer.from(data), err => {
// THIS PART DOES NOTHING
data.on('data',(d)=>{
progress += d.length;
console.log(`Progress: ${progress}`)
})
// --------------------
if (err) {
console.log(err);
return reject(err);
}
return resolve(fileName)
});
}
);
});
}
Looks like I can't find the way to show the progess of the download by calling on('data'....)...wondering now if this is the correct way to do this, or if this is even possible.
I tried putting the on('data'....) code as it is now inside the writeFile function but also inside the callback from drive.files.get and nothing works.

Answer 1

Here it comes some code sample to do that,
this example has three parts that need to be mentioned:
Create a stream to track our download progress
Create a method to get the file size
Create an event emitter to send back our progress to our FE
So we will get the following:
const downloadFile = async(file) => {
const fileId = file.id
const fileName = path.join(basePathForStorage, file.name)
let progress = 0
/**
* ATTENTION: here you shall specify where your file will be saved, usually a .temp folder
* Here we create the stream to track our download progress
*/
const fileStream = fs.createWriteStream(path.join(__dirname, './temp/', filename))
const fileSize = await getFileSize(file)
// In here we listen to the stream writing progress
fileStream.on('data', (chunk) => {
progress += chunk.length / fileSize
console.log('progress', progress)
})
const drive = google.drive({
version: 'v3',
authorization
})
drive.files.get({
auth: authorization,
fileId: fileId,
alt: 'media'
}, {
responseType: "stream"
},
(err, { data }) =>
data
.on('end', () => console.log('onCompleted'))
.on('error', (err) => console.log('onError', err))
.pipe(fileStream)
)
}
The method to retrieve the file size:
const getFileSize = ({ fileId: id }) => {
const drive = google.drive({
version: 'v3',
authorization
})
return new Promise((resolve, reject) =>
drive.files.get({
auth: authorization,
fileId
}, (err, metadata) {
if (err) return reject(err)
else resolve(metadata.size)
})
}
This code sample give you the ability to get partial updates from your file download as you're creating a write stream (nodejs#createWriteStream)
So you will be able to track your file downloading progress.
But, still you have to continuosly send these changes to your client ( FE ).
So, you could create your own EventEmitter to track that.
And now our sample will be enchanced with the following:
In our endpoint:
import { EventEmitter } from 'events'
router.post('/myEndpoint', (req, res) => {
res.writeHead(200, { 'Content-Type': 'text/plain' })
const progressEvent = new EventEmitter()
progressEvent.on('progress', (progress) => {
if (progress === 100)
res.end()
// So, your FE side will be receiving this message continuosly
else res.write(`{ progress: ${ progress } }`)
})
const file = req.body // or where you're getting your file from
downloadFile(file, progressEvent)
})
In our download method:
const downloadFile = async(file, progressEvent) => {
.
.
.
fileStream.on('data', (chunk) => {
progress += chunk.length / fileSize
progressEvent.emit('progress', progress)
.
.
.