Haven Push Relay

FCM push notification relay for Haven mobile apps. Runs as a Firebase Cloud Function so it stays online 24/7 even if your PC is off.

How it works

Haven Server A ──┐
Haven Server B ──┼── POST /sendPush ──→ Cloud Function ──→ FCM ──→ phones
Haven Server C ──┘

Self-hosted Haven servers don't need Firebase credentials. They just POST to this relay with a shared key. The relay holds the Firebase service account and forwards to FCM.

Setup

1. Install Firebase CLI

npm install -g firebase-tools
firebase login

2. Deploy

cd haven-push-relay
cd functions && npm install && cd ..
firebase deploy --only functions

3. Set the push key (a shared secret for authenticating servers)

Generate a random key and set it:

firebase functions:secrets:set HAVEN_PUSH_KEY

Enter a strong random string when prompted (e.g. output of openssl rand -hex 32).

Redeploy after setting the secret:

firebase deploy --only functions

4. Get the relay URL

After deploy, Firebase will print the function URL:

Function URL (sendPush): https://sendpush-xxxxxxxxxx-uc.a.run.app

5. Configure Haven servers

Each Haven server that wants mobile push notifications adds to their .env:

FCM_RELAY_URL=https://sendpush-xxxxxxxxxx-uc.a.run.app
FCM_PUSH_KEY=your-secret-key-from-step-3

That's it. Any message sent on that Haven server will trigger push notifications to mobile app users who aren't actively using the app.

Security

The relay key prevents unauthorized servers from sending pushes
Each request is validated (tokens array, title, body required)
Max 500 tokens per request (FCM limit)
Failed/expired tokens are reported back so servers can clean them up
CORS is enabled so it works from any origin
Max 10 concurrent instances to prevent abuse