Graceful degradation in Rest API - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this REST API error handling code?

Consider a REST API endpoint that tries to fetch user data. If the database is down, it returns a fallback message. What will be the JSON response when the database is unreachable?

Rest API

from flask import Flask, jsonify
app = Flask(__name__)

@app.route('/user/<int:user_id>')
def get_user(user_id):
    try:
        # Simulate database call
        raise ConnectionError('DB down')
    except ConnectionError:
        return jsonify({'message': 'Service temporarily unavailable, please try later'}), 503

if __name__ == '__main__':
    app.run()

A {"message": "Service temporarily unavailable, please try later"}

B {"error": "Database connection failed"}

C {"user_id": 1, "name": "John Doe"}

D 500 Internal Server Error

💡 Hint

Look at the except block and what JSON it returns.

The code catches the database connection error and returns a JSON message with a 503 status code. So the output is the JSON with the message about temporary unavailability.

🧠 Conceptual

intermediate

Which best describes graceful degradation in REST APIs?

Choose the statement that best explains the concept of graceful degradation in REST APIs.

A The API provides a simpler or fallback response when some components fail.

B The API stops working completely when a service fails.

C The API ignores errors and returns empty responses.

D The API crashes and returns a 500 error for all requests.

💡 Hint

Think about how the API behaves when something goes wrong but still tries to respond usefully.

Graceful degradation means the API still works in a limited way, providing fallback data or messages instead of failing completely.

🔧 Debug

advanced

Why does this graceful degradation code fail to return fallback data?

Examine the following Flask REST API code. It is supposed to return fallback data if the main service fails. Why does it not return the fallback data?

Rest API

from flask import Flask, jsonify
app = Flask(__name__)

@app.route('/data')
def get_data():
    try:
        # Simulate failure
        raise Exception('Service error')
    except Exception:
        fallback = {'data': 'default'}
    return jsonify(fallback)

if __name__ == '__main__':
    app.run()

A The try block should return fallback data directly, not in except.

B The variable 'fallback' is not defined if no exception occurs, causing a NameError.

C The jsonify function is called outside the except block, causing a syntax error.

D The except block does not return a response, so the function returns None.

💡 Hint

What happens if the try block does not raise an exception?

If no exception occurs, the variable 'fallback' is never assigned, so the return statement tries to jsonify an undefined variable, causing a NameError.

📝 Syntax

advanced

Which option fixes the syntax error in this graceful degradation snippet?

Identify the option that fixes the syntax error in this Python REST API snippet using graceful degradation.

Rest API

def fetch_data():
    try
        data = get_remote_data()
    except Exception:
        data = {'message': 'Fallback data'}
    return data

A Indent the except block at the same level as try.

B Remove the except block entirely.

C Change try to try():

D Add a colon after try: <br> def fetch_data():<br> &nbsp;&nbsp;try:<br> &nbsp;&nbsp;&nbsp;&nbsp;data = get_remote_data()<br> &nbsp;&nbsp;except Exception:<br> &nbsp;&nbsp;&nbsp;&nbsp;data = {'message': 'Fallback data'}<br> &nbsp;&nbsp;return data

💡 Hint

Check the syntax for try-except blocks in Python.

The try statement must end with a colon. Option D adds the missing colon, fixing the syntax error.

🚀 Application

expert

How many fallback responses does this REST API provide?

Given the following Flask REST API code, how many different fallback JSON responses can the API return when the main service fails?

Rest API

from flask import Flask, jsonify
app = Flask(__name__)

@app.route('/info')
def info():
    try:
        # Simulate service failure
        raise ValueError('Service error')
    except ValueError:
        return jsonify({'error': 'Service temporarily unavailable'}), 503
    except Exception:
        return jsonify({'error': 'Unknown error occurred'}), 500

if __name__ == '__main__':
    app.run()

A 0

B 2

C 1

D 3

💡 Hint

Which except block will run given the raised exception?

The code raises a ValueError, so only the first except block runs, returning one fallback response.