Pub/Sub Demo with Golang and DragonFlyDB

This project demonstrates the Publisher/Subscriber pattern using Golang and DragonFlyDB. It consists of two services:

1. Publisher Service (pub.go) - Publishes messages to a channel
2. Subscriber Service (subscriber.go) - Subscribes to the channel and processes messages

Prerequisites

• Go 1.21 or higher
• Docker and Docker Compose (for containerized deployment)
• DragonFlyDB (automatically set up with Docker Compose)

How It Works

1. The Publisher service connects to DragonFlyDB and periodically publishes JSON messages to a specified channel.
2. The Subscriber service connects to the same DragonFlyDB instance and subscribes to the channel.
3. When the Publisher sends a message, DragonFlyDB distributes it to all Subscribers.
4. The Subscriber receives the message, processes it, and measures the latency.

Key Concepts Demonstrated

• Pub/Sub Pattern: Decouples message senders (publishers) from receivers (subscribers)
• Message Distribution: One message can be received by multiple subscribers
• Asynchronous Communication: Publishers and subscribers operate independently
• Scalability: Easy to add more publishers or subscribers without changing the code

Running the Demo

Using Docker Compose

# Start all services
docker compose up

# To run with multiple subscriber instances
docker compose up --scale subscriber=3

Running Locally

1. Start DragonFlyDB:

docker run -p 6379:6379 docker.dragonflydb.io/dragonflydb/dragonfly

2. Run the subscriber:

go run subscriber.go

3. Run the publisher:

go run pub.go

Configuration

Both the publisher and subscriber retrieve configuration via environment variables. The following environment variables control the configuration:

• REDIS_ADDR - DragonFlyDB address (default: "localhost:6379")
• CHANNEL - Channel name (default: "messages")

Example environment variable usage:

export REDIS_ADDR=localhost:6379
export CHANNEL=custom-channel
go run pub.go
go run subscriber.go

Message Format

Messages are JSON-encoded with the following structure:

{
  "id": "msg-123",
  "content": "This is message #123",
  "timestamp": "2023-04-18T12:34:56.789Z"
}

Graceful Shutdown

Both services handle SIGINT and SIGTERM signals for graceful shutdown:

1. Stop publishing/receiving messages.
2. Unsubscribe from channels (for subscribers).
3. Close DragonFlyDB connections.
4. Exit cleanly.

Extensions and Improvements

• Add message acknowledgment
• Implement message persistence
• Add message filtering capabilities
• Implement message replay functionality
• Create a web interface to monitor message flow