A2 Service — Postgres Integration

How to Run

1. Clone the repository.
2. Copy the .env.example file as .env (not required when running with Docker Compose; used only for local development outside Docker).
3. Start the entire stack:

```bash docker compose up --build -d ```

4. The API will be available at localhost:3000.

Architecture

• src/service/ItemService.js — business logic, storage-agnostic
• src/routes/items.js — HTTP routes, storage-agnostic
• src/repositories/InMemoryItemRepository.js — egacy in-memory implementation (deprecated, kept for reference)
• src/repositories/PostgresItemRepository.js — new Postgres implementation

In-memory'den Postgres'e geçiş

Only the repository selection in the src/index.js file was changed:

```js // Before const repository = new InMemoryItemRepository();

// After const pool = new Pool({ connectionString: process.env.DATABASE_URL }); const repository = new PostgresItemRepository(pool); ```

The ItemService.js and routes/items.js files remained completely unchanged. This was possible because the repository interface (create/findAll/findById) is identical in both implementations.

Persistence Testing

1. The stack was started using docker compose up -d.
2. Data was added via 3 POST requests (test-1, test-2, test-3).
3. Verified that all 3 records were returned using GET /items.
4. Both app and db containers were completely stopped and removed using docker compose down (volumes were not deleted).
5. The stack was restarted using docker compose up -d.
6. Called GET /items again — all 3 records were still returned.

Proof (terminal output):

``` $ curl localhost:3000/items [{"id":1,"name":"test-1","created_at":"..."}, {"id":2,"name":"test-2","created_at":"..."}, {"id":3,"name":"test-3","created_at":"..."}]

$ docker compose down [+] Running 2/2 ✔ Container a2-service-app-1 Removed ✔ Container a2-service-db-1 Removed

$ docker compose up -d [+] Running 2/2 ✔ Container a2-service-db-1 Started ✔ Container a2-service-app-1 Started

$ curl localhost:3000/items [{"id":1,"name":"test-1","created_at":"..."}, {"id":2,"name":"test-2","created_at":"..."}, {"id":3,"name":"test-3","created_at":"..."}] ```

Data was preserved because the stack was stopped with docker compose down, not docker compose down -v (which would delete the pgdata volume).

Environment Variables

See the .env.example file. The actua .env file is in .gitignore and not committed to the repository.