IBM Watson tokens expire in one hour. Code to refresh the tokens? - ibm-watson

Question

I'm setting up IBM Watson Speech-to-Text. This requires an access token, documented here:
"Tokens have a time to live (TTL) of one hour, after which you can no longer use them to establish a connection with the service. Existing connections already established with the token are unaffected by the timeout. An attempt to pass an expired or invalid token elicits an HTTP 401 Unauthorized status code from DataPower. Your application code needs to be prepared to refresh the token in response to this return code."
I don't see on the documentation page an example of application code to refresh the token.
Should my code generate a new token for every user who downloads the JavaScript app? Or should the server request a new token every hour, and give all users the same token for an hour?
The shell command to get a token is:
curl -X GET --user username:password \
--output token \
"https://stream.watsonplatform.net/authorization/api/v1/token?url=https://stream.watsonplatform.net/speech-to-text/api"
That looks like I can send an HTTP request from my JavaScript app and get back a token. Should I request the token as a file, and then have my app get the token from the file?

Answer 1

enter code hereWhat worked was to use Cloud Functions for Firebase (part of Google Cloud Functions), triggered on a user logging in, running Node to send an HTTP request to get the token and then write the result to an AngularJS value service.
This Cloud Function works:
// 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
var username = 'groucho',
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) {
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
}); // close getWatsonToken
In the controller:
firebase.auth().onAuthStateChanged(function(user) { // this runs on login
if (user) { // user is signed in
console.log("User signed in!");
$scope.authData = user;
firebase.database().ref('userLoginEvent').update({'user': user.uid}); // update Firebase database to trigger Cloud Function to get a new IBM Watson token
} // end if user is signed in
else { // User is signed out
console.log("User signed out.");
}
}); // end onAuthStateChanged
Walking through the Cloud Function, it injects four Node modules, including request for sending HTTP requests, and fs for writing the results to a file. Then the trigger is set for an update to a location userLoginEvent in the Firebase database (which I created from the console). Next, the HTTP request goes out. The response (the token) is called body. app.value('watsonToken','" + body + "');" is an Angular value service to wrap the token. Then fs writes all this to a location in my project.
In the AngularJS controller, onAuthStateChanged triggers when a user logins in. The user.uid is then updated to the location userLoginEvent in the Firebase database, and the Cloud Function triggers, the HTTP request goes out, and the response is written to an Angular service.