Connection lifecycle management in FastAPI - Mini Project: Build & Apply

Connection lifecycle management in FastAPI

📖 Scenario: You are building a simple FastAPI application that needs to manage a database connection properly. You want to open the connection when the app starts and close it when the app shuts down.

🎯 Goal: Create a FastAPI app that opens a connection on startup and closes it on shutdown using event handlers.

📋 What You'll Learn

Create a FastAPI app instance named app

Define a variable db_connection initialized to None

Add a startup event handler function named connect_to_db that sets db_connection to the string 'Database Connected'

Add a shutdown event handler function named close_db_connection that sets db_connection to None

Register the startup and shutdown event handlers with the app instance

💡 Why This Matters

🌍 Real World

Managing database or external service connections properly is essential in web applications to avoid resource leaks and ensure smooth operation.

💼 Career

Understanding connection lifecycle management is important for backend developers working with FastAPI or similar frameworks to build reliable and maintainable APIs.

1

Create FastAPI app and initialize connection variable

Create a FastAPI app instance called app and create a variable called db_connection set to None.

FastAPI

from fastapi import FastAPI

# Create FastAPI app instance
# Your code here

Need a hint?

Use app = FastAPI() to create the app and db_connection = None to initialize the connection variable.

2

Define startup event handler to open connection

Define a function called connect_to_db decorated with @app.on_event('startup') that sets db_connection to the string 'Database Connected'.

FastAPI

from fastapi import FastAPI

app = FastAPI()
db_connection = None

# Define startup event handler
# Your code here

Need a hint?

Use @app.on_event('startup') to decorate the function and assign the string to db_connection inside the function.

3

Define shutdown event handler to close connection

Define a function called close_db_connection decorated with @app.on_event('shutdown') that sets db_connection to None.

FastAPI

from fastapi import FastAPI

app = FastAPI()
db_connection = None

@app.on_event('startup')
def connect_to_db():
    global db_connection
    db_connection = 'Database Connected'

# Define shutdown event handler
# Your code here

Need a hint?

Use @app.on_event('shutdown') to decorate the function and set db_connection to None inside it.

4

Add a simple root path to verify app runs

Add a path operation function called read_root decorated with @app.get('/') that returns a dictionary with the key 'status' and the value of db_connection.

FastAPI

from fastapi import FastAPI

app = FastAPI()
db_connection = None

@app.on_event('startup')
def connect_to_db():
    global db_connection
    db_connection = 'Database Connected'

@app.on_event('shutdown')
def close_db_connection():
    global db_connection
    db_connection = None

# Add root path operation
# Your code here

Need a hint?

Use @app.get('/') to decorate the function and return a dictionary with the current db_connection value.