Startup and shutdown events in FastAPI - Cheat Sheet & Quick Revision

Recall & Review

beginner

What are startup events in FastAPI?

Startup events are functions that run once when the FastAPI app starts. They are used to set up resources like database connections or caches before the app handles requests.

beginner

How do you register a startup event in FastAPI?

Use the @app.on_event('startup') decorator above an async function. This function will run automatically when the app starts.

beginner

What are shutdown events in FastAPI?

Shutdown events are functions that run once when the FastAPI app is stopping. They help clean up resources like closing database connections or saving state.

beginner

How do you register a shutdown event in FastAPI?

Use the @app.on_event('shutdown') decorator above an async function. This function will run automatically when the app is stopping.

intermediate

Why are startup and shutdown events important in FastAPI?

They help manage resources safely and efficiently by preparing needed services before requests and cleaning up after the app stops, preventing errors and leaks.

Which decorator is used to define a startup event in FastAPI?

A @app.on_start()

B @app.startup()

C @app.event('start')

D @app.on_event('startup')

The correct decorator is @app.on_event('startup') to register a startup event.

When does a shutdown event run in a FastAPI app?

A When the app stops

B When the app starts

C Before each request

D After each response

Shutdown events run once when the app is stopping to clean up resources.

Can startup and shutdown event functions be synchronous in FastAPI?

A Only startup can be sync

B No, they must be async

C Yes, but async is recommended

D Only shutdown can be sync

They can be synchronous, but async functions are recommended for non-blocking operations.

What is a common use case for a startup event?

A Closing database connections

B Opening database connections

C Handling HTTP requests

D Logging user activity

Startup events often open database connections or initialize resources.

What happens if you forget to close resources in a shutdown event?

A It can cause resource leaks or errors

B The app will restart

C Resources close automatically

D Nothing, shutdown events are optional

Not closing resources can cause leaks or errors, so shutdown events help prevent that.

Explain how to use startup and shutdown events in FastAPI and why they matter.

Think about preparing and cleaning up resources around the app lifecycle.

Describe a real-life example where startup and shutdown events improve a FastAPI app.

Imagine your app needs a database to work smoothly.