Calling `Firebase.initializeApp` more than once causes `default Firebase app already exists` error.

[ccorcos]

ProductName: Mac OS X
ProductVersion: 10.14.4
BuildVersion: 18E226
"firebase-admin": "5.12.1",

When I call Firebase.initializeApp() more than once, I get this error:

Error: The default Firebase app already exists. This means you called initializeApp() more than once without providing an app name as the second argument. In most cases you only need to call initializeApp() once. But if you do want to initialize multiple apps, pass a second argument to initializeApp() to give each app a unique name.

Its really annoying because I want to create isolated servers for each test without having to run a separate instance of Node. Can you please fix this so more than one can run side-by-side?

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[hiranya911]

There's nothing to fix. This is how this API is expected to work. If you want to run multiple instances of FirebaseApp, you need to give them different names. See https://firebase.google.com/docs/reference/admin/node/admin.app.App.html#name for some examples.

[ccorcos]

Interesting. So I can make up a random string each time?

[hiranya911]

That's up to you. As far as the SDK is concerned, each instance of FirebaseApp must have a different name.

[Johnrobmiller]

There's nothing to fix. This is how this API is expected to work. If you want to run multiple instances of FirebaseApp, you need to give them different names. See https://firebase.google.com/docs/reference/admin/node/admin.app.App.html#name for some examples.

Your app is breaking on Next.js projects with this error. There is nothing in the docs that clues people in on how to fix it. So there actually is something for you guys to fix.

[DrjavaB]

There's nothing to fix. This is how this API is expected to work. If you want to run multiple instances of FirebaseApp, you need to give them different names. See https://firebase.google.com/docs/reference/admin/node/admin.app.App.html#name for some examples.

the link you sent doesn't work...

[jstncno]

Based on comments on this thread, the answer provided is not very helpful, i.e. this error breaks Next.js projects with no help info and the provided link leads to a 404.

For those wanting a quick fix, the workaround of first checking if any apps were initialized did the trick for me:

if (!getApps().length) initializeApp();

I've resurrected this issue with a more narrow scope stating that this error breaks Next.js apps:
#2111

[YoungiiJC]

I am also getting this error in Firebase Functions.

export const someFirebaseFunction = functions.https.onRequest(
  async (request, response) => {
    ...
    initializeApp();
    ...
  }
)

A way to resolve this issue is to make the function async and try and catch the error but also continue doing your task:

try {
      admin.initializeApp({
        credential: admin.credential.cert(cred),
      });
      return respond();
    } catch (e) {
      return respond();
    }

function respond(){
// perform your task
}