NATS Order and Inventory Example

Small Go example that shows service-to-service messaging with NATS.

The order service publishes an orders.created event every few seconds. The inventory service subscribes to that event and reduces stock for the ordered product.

Stack

• Go
• NATS
• Docker Compose

Run

docker compose up --build

You should see the order service publishing events and the inventory service receiving them.

Services

Service	Purpose
nats	Message broker
order-service	Publishes new order events
inventory-service	Subscribes to order events and updates stock

Event

Subject:

orders.created

Payload:

{
  "order_id": 101,
  "product_id": 51,
  "quantity": 1
}

Notes

• NATS_URL is configured in docker-compose.yml.
• Local logs and binaries are ignored by Git.
• This is intentionally small so the message flow is easy to follow.

Troubleshooting

• If a service exits early, run docker compose logs <service-name>.
• If events are not received, confirm both services use NATS_URL=nats://nats:4222.
• If port 4222 is already in use, change the exposed port in docker-compose.yml.