# Day 12 : Docker Compose

Since, we Dockerized all services, let’s use **Docker Compose** to run them together locally with one command, simulating a microservices environment. This introduces orchestration (a taste of Kubernetes) while reinforcing Docker

**Objective**

* Create a docker-compose.yml to orchestrate User, Product, Order, and Recommend Services.

* Run and test all services as a system, commit to GitHub

* Each container (e.g., order-service, product-service) runs in its own isolated environment with its own network stack.

* Inside the order-service container, localhost refers to *itself*, not the host machine or other containers. So, <http://localhost:8080/users> tries to find a service running at port 8080 *inside* the Order Service container, which doesn’t exist—hence the Error: User Service unavailable

* Containers run in a virtual network. Service names act like DNS entries, enabling communication (e.g., Order calls User via user-service:8080).

* This setup mirrors real-world microservices, where services discover each other dynamically (e.g., via DNS, service registries)

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### Let's make our application Dynamic (CRUD Functionality)

Let’s add **CRUD** operations (Create, Read, Update, Delete) to both services, allowing users to:

* **Add** new users/products.
* **Retrieve** all or specific users/products.
* **Update** existing ones.
* **Delete** them. This will make your e-commerce app interactive

Approach :&#x20;

* **Storage**: Use in-memory lists (e.g., Python dictionaries, Java HashMaps) for simplicity—no database yet (we’ll add one in Phase 5).
* **APIs**: Add REST endpoints (POST, GET, PUT, DELETE) to User and Product Services.
* **Order/Recommend**: Update to handle dynamic data (e.g., fetch by ID).
* **Compose**: Keep running all services seamlessly.

### User-service

* Adds express.json() for parsing POST/PUT bodies.
* Stores products in an array.
* Endpoints:
  * GET /products: List all.
  * GET /products/:id: Get by ID.
  * POST /products: Create ({"name": "Phone", "price": 499}).
  * PUT /products/:id: Update.
  * DELETE /products/:id: Delete.

### orders-service

* Changed to POST /orders—accepts {"user\_id": 1, "product\_id": 101}.
* Calls specific user/product by ID.
* Validates input, returns 404 if not found.

**Purpose**: Serves a webpage at <http://localhost:8080/> with:

* A table listing users.
* Forms to add (name) and update (ID + name).
* Delete buttons per user.
* JavaScript for API calls to /users

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