🔐 FCM Gateway

A secure, lightweight, and scalable Firebase Cloud Messaging (FCM) gateway built with Node.js, using MySQL for subscriber management, Redis for message queuing, and Winston for structured logging.

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📦 Features

• ✅ Token-based authentication for all endpoints
• ✅ Send to one or all subscribers
• ✅ FCM push messaging with auto-removal of invalid tokens
• ✅ MySQL: persistent subscriber store
• ✅ Redis: batch queuing of messages (1,000-token chunks)
• ✅ Worker daemon that processes queued pushes
• ✅ Winston logging (colorized console + file logging)
• ✅ .env configuration
• ✅ PM2 & Docker support
• ✅ Heartbeat & stats endpoints

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🛠 Tech Stack

• Node.js
• Express
• Firebase Admin SDK
• MySQL
• Redis
• Winston Logger
• dotenv
• helmet
• PM2
• Docker

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🚀 Getting Started

1. Clone the repo

git clone https://github.com/yourname/fcmGateway.git
cd fcmGateway

2. Install dependencies

npm install

3. Add your Firebase service account

Download the serviceAccountKey.json from Firebase Console and place it in the root folder.

4. Create a .env file

PORT=3000
API_KEY=yourSecretApiKey123

# MySQL
DB_HOST=127.0.0.1
DB_PORT=3306
DB_USER=fcm_user
DB_PASS=fcm_pass
DB_NAME=fcm_gateway

# Redis
REDIS_HOST=127.0.0.1
REDIS_PORT=6379
REDIS_USERNAME=default
REDIS_PASSWORD=supersecret
REDIS_CHANNEL=fcm_push_queue

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📡 API Endpoints

POST /subscribe

Registers a device for push notifications.

{
  "deviceToken": "fcm_token_here",
  "clientId": "unique_device_id"
}

POST /unsubscribe

Removes a device token from the database.

{
  "deviceToken": "fcm_token_here"
}

POST /send

Sends a push message to a single device.

{
  "deviceToken": "fcm_token_here",
  "clientId": "device-12345",
  "data": {
    "id": 85200258,
    "eventTime": "2025-05-19 12:28:15",
    "title": "Message content test 3",
    "body": "A 4.4 magnitude earthquake struck the volcanic area around Naples as part of a 'major' quake swarm on Tuesday, sparking fear but no immediate reports of damage. The tremor hit the Campi Flegrei area in southern Italy at 12:07 pm, at a depth of three kilometres, according to Italy's National Institute of Geophysics and Volcanology.<br><br>Underground activity<br><br><br><a href=\"https://map.crisisinfo.eu\">Jump link</a>",
    "event": "earthquake",
    "lat": 40.8270141,
    "lon": 14.1195161,
    "categoryCode": "EQ",
    "messageLevel": 3
  }
}

🛡 Requires: x-api-key header

POST /send-all

Queues a broadcast message to all subscribers (in 1,000-token chunks) via Redis.

{
  "data": {
    "id": 85200258,
    "eventTime": "2025-05-19 12:28:15",
    "title": "Message content test 3",
    "body": "A 4.4 magnitude earthquake struck the volcanic area around Naples as part of a 'major' quake swarm on Tuesday, sparking fear but no immediate reports of damage. The tremor hit the Campi Flegrei area in southern Italy at 12:07 pm, at a depth of three kilometres, according to Italy's National Institute of Geophysics and Volcanology.<br><br>Underground activity<br><br><br><a href=\"https://map.crisisinfo.eu\">Jump link</a>",
    "event": "earthquake",
    "lat": 40.8270141,
    "lon": 14.1195161,
    "categoryCode": "EQ",
    "messageLevel": 3
  }
}

GET /heartbeat

Returns basic service status and current timestamp.

GET /stats

Returns current subscriber count from the database.

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🧠 Redis Queue Worker

The worker.js script runs independently and continuously listens to the Redis queue to process push messages.

Start manually:

node worker.js

Or via PM2:

pm2 start ecosystem.config.js

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📁 Database: fcm_subscribers

Column	Type	Description
id	INT (PK)	Auto increment
device_token	VARCHAR(255)	Firebase device token
client_id	VARCHAR(64)	Unique device identifier
subscribed_at	DATETIME	Subscription timestamp
last_seen	DATETIME	Last active ping/renewal

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🧰 Running with PM2

Start both app and worker with:

pm2 start ecosystem.config.js
pm2 save
pm2 startup

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🐳 Running with Docker

1. Build and start services

docker-compose up -d --build

2. Services included:

• fcm-api: Express-based REST API
• fcm-worker: Background worker for Redis queue
• redis: In-memory message queue

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🔍 Monitoring

pm2 list
pm2 logs fcmGateway
pm2 logs fcmWorker

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📄 License

MIT – free to use, modify, and share.

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💬 Author

Made with ☕ and ❤️ by Zsolt Boszormenyi · Contact: hunnomad@gmail.com