> ## Documentation Index
> Fetch the complete documentation index at: https://notes.kodekloud.com/llms.txt
> Use this file to discover all available pages before exploring further.
# Understanding the Course Usecase
> This article explains a microservices architecture using Dockerized Node.js and Spring Boot services with REST API communication.
In this lesson, we’ll walk through our example architecture and the HTTP endpoints each service exposes. We have two simple Dockerized microservices:
1. A Node.js service (runs on port 5000)
2. A Spring Boot service (runs on port 8080)
Both services communicate via REST APIs, demonstrating best practices for containerization and orchestration.
***
## Node.js Microservice (Port 5000)
This lightweight Node.js application is packaged in Docker and listens on port 5000. It offers a single endpoint:
**GET /plusone/{number}**
* **Function**: Takes an integer and returns its value plus one.
* **Example Request**:
```bash theme={null}
curl http://localhost:5000/plusone/41
# 42
```
Ensure Docker is running and the container is listening on port 5000 before invoking this endpoint.
***
## Spring Boot Microservice (Port 8080)
The Spring Boot application exposes three REST endpoints on port 8080. It illustrates service-to-service calls and conditional logic.
| Endpoint | Description | Example |
| ----------------------- | ------------------------------------------------------------------------------------- | ------------------------------------------------------------------- |
| GET / | Returns a welcome message | `curl http://localhost:8080/` |
| GET /increment/{number} | Forwards `{number}` to Node.js `/plusone` endpoint and returns the incremented result | `curl http://localhost:8080/increment/41` → `42` |
| GET /compare/{number} | Compares `{number}` against 50 and returns a descriptive message | `curl http://localhost:8080/compare/77` → `"77 is greater than 50"` |
### 1. GET /
Returns a simple greeting from the Spring Boot service:
```bash theme={null}
curl http://localhost:8080/
# "Welcome to the Spring Boot service!"
```
### 2. GET /increment/{number}
This endpoint demonstrates inter-service communication. It sends the provided number to the Node.js `/plusone` service and returns the incremented result.
```bash theme={null}
curl http://localhost:8080/increment/41
# 42
```
### 3. GET /compare/{number}
Performs a conditional check on the input number:
* If `number` ≤ 50: returns `"{number} is less than or equal to 50"`.
* If `number` > 50: returns `"{number} is greater than 50"`.
```bash theme={null}
curl http://localhost:8080/compare/50
curl http://localhost:8080/compare/77
# "77 is greater than 50"
```
Port conflicts can occur if other services use ports 5000 or 8080. Always verify available ports before starting the containers.
***
## Course Roadmap
Throughout this course, you will:
* Containerize and Dockerize the Spring Boot application.
* Deploy Spring Boot securely on Kubernetes with best practices.
* Leverage an existing Docker image for the Node.js service.
* Explore service-to-service REST communication and error handling.
By the end, you’ll have a fully functioning microservices demo running on Kubernetes, complete with automated builds and deployments. Let’s dive in!
***
## Links and References
* [Node.js Official Site](https://nodejs.org/)
* [Spring Boot Documentation](https://spring.io/projects/spring-boot)
* [Docker Documentation](https://docs.docker.com/)
* [Kubernetes Basics](https://kubernetes.io/docs/concepts/overview/what-is-kubernetes/)