Distributed tracing demo services

This repository contains three Spring Boot 3.2.0 services built with Java 21 that demonstrate REST, gRPC, WebSocket, and NATS (message queue) interactions.

Modules

• common-proto – Shared gRPC contracts compiled from protobuf definitions.
• inventory-service – Exposes REST and gRPC endpoints for inventory status and listens to NATS messages.
• operation-service – Invokes the inventory service via REST and gRPC and publishes updates to NATS.
• gateway-service – Provides REST, gRPC, and WebSocket interfaces for clients.

Building

mvn clean package

Running the services

Each service can be launched separately. They expect supporting infrastructure (such as NATS) to already be running.

# terminal 1
mvn -pl inventory-service spring-boot:run

# terminal 2
mvn -pl operation-service spring-boot:run

# terminal 3
mvn -pl gateway-service spring-boot:run

Environment variables can be used to override defaults:

• NATS_URL – NATS server URL (default nats://localhost:4222).
• INVENTORY_HTTP_BASE_URL – Inventory REST URL for the operation service.
• INVENTORY_GRPC_TARGET – Inventory gRPC target for the operation service.

Sample interactions

# Trigger the operation workflow (REST -> REST + gRPC + NATS)
curl http://localhost:8080/operations/execute/demo-item

# Call inventory REST endpoint directly
curl http://localhost:8081/inventory/status/demo-item

# Call gateway REST endpoint
curl http://localhost:8082/api/ping?name=Tempo

For gRPC, use any compatible client targeting the ports defined in each service (9091, 9092). WebSocket clients can connect to ws://localhost:8082/ws/ping and send text payloads.