Invoking CloudFunctions from Web Application resulting in CORS

[Dalton Fury]

Firebase is "randomly" giving CORS issue when connecting to cloud functions from a Web App.

I have functions defined like this:

const functions = require("firebase-functions");
const admin = require("firebase-admin");


admin.initializeApp();


exports.createQueue = functions.https.onCall((data, context) => {
    ...
});

and I am calling the function from a web client like this:

        firebase.initializeApp(firebaseConfig);
        this.queues = firebase.firestore().collection("queuesFromFBFn");


        firebase.auth().signInAnonymously().catch(error => console.error(error));
        this.functions = firebase.app().functions();


        const createQueueFn = this.functions.httpsCallable('createQueue');
        return createQueueFn({
            name: name,
        }).then(response => response.data.data)

Invoking the function is giving CORS errors randomly. They go away for a while if I remove the cloud function and reupload it by changing just the function name, suggesting that the problem is not with the code. The function is working fine when ran locally using the emulator too. The function is Invokable by allUsers in the GCP console.

I have been trying to fix it for the last four days. Is it becasue of some misconfiguration which I can't get my head around?

[Michael Bleigh]

You might get CORS errors if the function crashes in am unexpected way. Do you see anything in the function logs when you get these kinds of errors?

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[Dalton Fury]

Hey Michael,

THe logs are clean, I put a console.log right at line 1, it's not running.

The issue goes away on deleting the function and redeploying it, also it goes away naturally after some time, hence I am suspecting that it's because of something else.

Yes, I figured out that if the function crashes, it gives a CORS error, but it might not be the case as the function with the same input works locally on the firebase shell. 

I have anonymous authentication enabled. Is it because of that, for some reason?

Thanks,

Fury

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[Emiliano Hernandez]

One thing you can do, that has worked for me:

1. Lint the function with eslint..
2. Check the function name is the same one you are calling, if you are calling a non existing function you get CORS. (This is where 99% of my CORS errors come from)

If you are sure firebase is doing something wrong delete the function from the console and redeploy.