Can't read hosting files in a cloud Function

Question

My Firebase function isn't working. Here's the log:

11:01:03.932 AM warning getWatsonToken Error: ENOENT: no such file or directory, open '../public/javascript/services/watsonTokenValue.js'
    at Error (native)

11:01:03.831 AM warning getWatsonToken Uncaught exception

11:01:03.233 AM info    getWatsonToken 5YGY3R%2FBP0zelDOaob9PnxMWDj...

11:01:00.139 AM outlined_flag getWatsonToken Function execution took 804 ms, finished with status: 'ok'

11:00:59.834 AM info    getWatsonToken Executing function!

11:00:59.335 AM outlined_flag getWatsonToken Function execution started

I don't know what "Uncaught exception" is referring to.

The "ENOENT: no such file or directory" error might be a Node path mistake. Here's my directory structure:

── functions
    ├── index.js // this is my function
── public
    ├── javascript
    │   ├── services
    │   │   ├── watsonTokenValue.js // this is the file I want to write to

And here's the line that's apparently causing the error:

fs.writeFile('../public/javascript/services/watsonTokenValue.js', tokenService, (err) => {

The line uses Node to write a file. Is there something wrong with the path?

Here's the full function:

// Node modules
const functions = require('firebase-functions');
const admin = require('firebase-admin');
const request = require('request'); // node module to send HTTP requests
const fs = require('fs');

admin.initializeApp(functions.config().firebase);

exports.getWatsonToken = functions.database.ref('userLoginEvent').onUpdate(event => { // authentication trigger when user logs in
  console.log("Executing function!");
  var username = '56ae6a1e7854',
  password = 'swordfish',
  url = 'https://' + username + ':' + password + '@stream.watsonplatform.net/authorization/api/v1/token?url=https://stream.watsonplatform.net/speech-to-text/api';

  request({url: url}, function (error, response, body) {
    console.log(body);
    var tokenService = "app.value('watsonToken','" + body + "');";

    fs.writeFile('../public/javascript/services/watsonTokenValue.js', tokenService, (err) => {
      if (err) throw err;
      console.log('The file has been saved!');
    }); // close fs.writeFile

  }); // close request
return 0; // prevents an error message "Function returned undefined, expected Promise or value"
}); // close getWatsonToken

The first four lines load Node modules. The function is called "getWatsonToken." It triggers when a user logs in, or, specifically, when a line of code in the login process writes the user's Auth ID to a location in Firebase Realtime Database, and then onUpdate triggers the function. Next, parameters are defined for an HTTP request, and then the HTTP request is sent to IBM Watson. IBM returns a token for its speech-to-text service as the body of the HTTP response. (A console.log shows the token, that's working.) Some Angular JavaScript then is wrapped around the token. Lastly, the file is written to a location in a directory. The last step seems to be where the error is.

Here's another view of my directory structure:

Thanks for your help!

Answer 1

You can't use a Cloud Function to read and write files served by Firebase Hosting, even in the same project.

When you use the Firebase CLI to deploy, each product is deployed separately. So, all your static content for Firebase Hosting in your public folder gets sent to one place, and all your Cloud Functions code gets sent to another place. After that, they share nothing in common.

You can read files under the functions folder after deployment. But obviously, those have nothing to do with Hosting after deployment.

I strongly recommend against trying to write files in a Cloud Function, especially for your use case. What you're trying to do is better served by writing persistent data to Realtime Database, Firestore, or even Cloud Storage. Disk files in Cloud Functions are not persistent, and you may have multiple instances of servers running functions that know nothing of each other.