Firebase Cloud Function Serving Local File for Download

Question

I created cloud function that generates an xlsx file, I need the user to download that file after it's generated.

Method 1: Upload to Bucket, then redirect

So far i've tried uploading the file to a bucket using this API , and then redirect him to the bucket file url, I also double checked the bucket name using this API , but I get the same error every time:

{"error":{"code":500,"status":"INTERNAL","message":"function crashed","errors":["socket hang up"]}}

Portion of the code that contains uploading to bucket:

    const { Storage } = require('@google-cloud/storage');
    const storage = new Storage();
    await storage.bucket('bucket-name').upload('myfile.xlsx', {
        gzip: false,
    });

Portion of the code that proves file exists:

    fs.access('myfile.xlsx', fs.constants.F_OK, (err) => {
        console.log(`${file} ${err ? 'does not exist' : 'exists'}`);
    });

I also checked if the library "@google-cloud/storage" reads the file, and it reads it correctly and gets the file size right.

Method 2: Direct Download

Download the file directly, the problem is that every doc online for nodejs to download a local file to the user is setting up a custom server to download the file, but i'm using firebase, so it's not in control of that server.

Answer 1

If your excel file is created and should be returned to the client as a response to an HTTP request (calling to an API endpoint) then this is how you can do it.

export const getExcelFile = functions.https.onRequest(async (request, response) => {
    // ...
    // Create your file and such
    // ..

    await storage.bucket('bucket-name').upload('myfile.xlsx', {
        gzip: false,
    });

    response.setHeader('Content-Type', 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet');
    response.send(fs.readFileSync('myfile.xlsx'));
    return null;
});

Otherwise, if the excel file is created as a response to an event, and you want the user to download the file at another time, then you create a download link and serve it to the user in any way you want.

// ...
// Create your file and such
// ..


const [file] = await storage.bucket('bucket-name').upload('myfile.xlsx', {
    gzip: false,
});
const [downloadUrl] = await file.getSignedUrl({ 
  action: 'read',
  expires: '20-03-2019' // Link expiry date: DD-MM-YYYY
});

console.log(downloadUrl);

Answer 2

Just wanted to add more detail to the answer, since there's no need to write into a file and read from it to download it's data, simply take the data and send it, using the few lines below.

    res.setHeader('Content-Type', 'application/vnd.openxmlformats');
    res.setHeader("Content-Disposition", "attachment; filename=" + fileName);
    res.end(fileData, 'binary');