Add .env-example file and update configuration for environment variables

- Created .env-example for environment variable setup
- Updated README to reflect changes in .env file creation
- Modified config.py to include new environment variables and DATABASE_URL property
- Enhanced database.py with connect and disconnect functions
- Updated main.py to manage database connection lifecycle
- Adjusted compose.yaml for consistent environment variable usage

.env-example

@@ -0,0 +1,5 @@
+postgres_user=exampleUser
+postgres_password=examplePasswd
+postgres_db=exampleDB
+db_port=5432
+api_port=8000

README.md

@@ -35,14 +35,14 @@ project/
 
 ### Setup
 
-Create a .env file in the root directory:
+Create a .env file, by copying .env-example, in the root directory and adjustign the vaulues as needed:
 
 ```text
-postgres_user=exampleUser
-postgres_password=examplePasswd
-postgres_db=exampleDB
-db_port=5432
-api_port=8000
+POSTGRES_USER=exampleUser
+POSTGRES_PASSWORD=examplePasswd
+POSTGRES_DB=exampleDB
+API_PORT=8000
+DEBUG=true
 ```
 
 Start the stack:
@@ -71,4 +71,4 @@ Do not run in production.
 The database schema is managed via Create.sql — no ORM migrations
 
 The .env file is excluded from version control via .gitignore
-```
+```

app/config.py

@@ -1,6 +1,23 @@
 from pydantic_settings import BaseSettings
+from pydantic import computed_field
 
 class Settings(BaseSettings):
-    DATABASE_URL: str = "${DATABASE_URL}"
+    POSTGRES_USER: str
+    POSTGRES_PASSWORD: str
+    POSTGRES_DB: str
+    API_PORT: int = 8000
+    DEBUG: bool = False
+
+    @computed_field
+    @property
+    def DATABASE_URL(self) -> str:
+        return (
+            f"postgresql+asyncpg://"
+            f"{self.POSTGRES_USER}:{self.POSTGRES_PASSWORD}"
+            f"@db/{self.POSTGRES_DB}"
+        )
+
+    class Config:
+        env_file = ".env"
 
 settings = Settings()

app/database.py

@@ -1,11 +1,22 @@
+from typing import AsyncGenerator
 from sqlalchemy.ext.asyncio import create_async_engine, AsyncSession
 from sqlalchemy.orm import sessionmaker
-from sqlalchemy import text
 from app.config import settings
 
-engine = create_async_engine(settings.DATABASE_URL, echo=True)
+engine = create_async_engine(settings.DATABASE_URL, echo=settings.DEBUG)
 AsyncSessionLocal = sessionmaker(engine, class_=AsyncSession, expire_on_commit=False)
 
-async def get_db():
+async def connect():
+    pass  # engine initializes at module level
+
+async def disconnect():
+    await engine.dispose()
+
+async def get_db() -> AsyncGenerator[AsyncSession, None]:
     async with AsyncSessionLocal() as session:
-        yield session
+        try:
+            yield session
+            await session.commit()
+        except Exception:
+            await session.rollback()
+            raise

app/main.py

@@ -1,14 +1,15 @@
 from contextlib import asynccontextmanager
 from fastapi import FastAPI
-from app.database import engine
+from app.database import connect, disconnect
 from app.routers import authors, books
 
 @asynccontextmanager
 async def lifespan(app: FastAPI):
-    yield # tables already created by Create.sql
-    await engine.dispose()
+    await connect()
+    yield
+    await disconnect()
 
 app = FastAPI(title="Database API", lifespan=lifespan)
 
-app.include_router(authors.router)
-app.include_router(books.router)
+for router in [authors.router, books.router]:
+    app.include_router(router)

compose.yaml

@@ -1,14 +1,12 @@
 services:
   api:
     restart: unless-stopped
-    container_name: api_${postgres_db}
+    container_name: api_${POSTGRES_DB}
     build: .
     env_file:
       - .env
     ports:
-      - "${api_port}:8000"
-    environment:
-      DATABASE_URL: postgresql+asyncpg://${postgres_user}:${postgres_password}@db:${db_port}/${postgres_db}
+      - "${API_PORT}:8000"
     depends_on:
       db:
         condition: service_healthy
@@ -17,20 +15,20 @@ services:
 
   db:
     image: postgres:18-alpine
-    container_name: postgres_${postgres_db}
+    container_name: postgres_${POSTGRES_DB}
     restart: unless-stopped
     shm_size: 128mb
-    ports:
-      - ${db_port}:5432
+    #ports:   #Not needed as the API container will connect to the DB container using the internal Docker network. Uncomment if you want to access the database from outside the Docker network.
+    #  - 5432:5432
     volumes:
       - ./postgresData:/var/lib/postgresql/data
       - ./Create.sql:/docker-entrypoint-initdb.d/Create.sql
     environment:
-      POSTGRES_USER: ${postgres_user}
-      POSTGRES_PASSWORD: ${postgres_password}
-      POSTGRES_DB: ${postgres_db}
+      POSTGRES_USER: ${POSTGRES_USER}
+      POSTGRES_PASSWORD: ${POSTGRES_PASSWORD}
+      POSTGRES_DB: ${POSTGRES_DB}
     healthcheck:
-      test: ["CMD-SHELL", "pg_isready -U ${postgres_user} -d ${postgres_db}"]
+      test: ["CMD-SHELL", "pg_isready -U ${POSTGRES_USER} -d ${POSTGRES_DB}"]
       interval: 10s
       timeout: 5s
       retries: 5