Health check endpoints in Flask - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a basic Flask app with a health check endpoint at '/health'.

Flask

from flask import Flask
app = Flask(__name__)

@app.route('/health')
def health_check():
    return [1]

Drag options to blanks, or click blank then click option'

A"OK"

B200

Capp.run()

Drequest

Attempts:

3 left

💡 Hint

Common Mistakes

Returning a status code number instead of a string

Calling app.run() inside the route function

The health check endpoint should return a simple string like "OK" to indicate the app is running.

2fill in blank

medium

Complete the code to run the Flask app only when the script is executed directly.

Flask

if __name__ == [1]:
    app.run(debug=True)

Drag options to blanks, or click blank then click option'

A__name__

B"main"

Capp

D"__main__"

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'main' without underscores

Using __name__ without quotes

The special variable __name__ equals "__main__" when the script is run directly.

3fill in blank

hard

Fix the error in the health check route to return a JSON response with status code 200.

Flask

from flask import jsonify

@app.route('/health')
def health_check():
    return jsonify(status='OK'), [1]

Drag options to blanks, or click blank then click option'

A200

B"OK"

C500

D404

Attempts:

3 left

💡 Hint

Common Mistakes

Using string 'OK' instead of numeric status code

Using error codes like 404 or 500

HTTP status code 200 means the request was successful.

4fill in blank

hard

Fill both blanks to create a health check endpoint that returns JSON with a message and status code 200.

Flask

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

@app.route([1])
def health():
    return jsonify([2]='Healthy'), 200

Drag options to blanks, or click blank then click option'

A"/health"

B"/status"

Cmessage

Dstatus

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong route path

Using 'status' as JSON key instead of 'message'

The route should be '/health' and the JSON key should be 'message' for clarity.

5fill in blank

hard

Fill all three blanks to create a Flask app with a health check endpoint that returns JSON with 'status', 'uptime', and HTTP 200.

Flask

from flask import Flask, jsonify
import time

app = Flask(__name__)
start_time = time.time()

@app.route([1])
def health_check():
    uptime = time.time() - [2]
    return jsonify([3]='OK', uptime=uptime), 200

Drag options to blanks, or click blank then click option'

A"/health"

Bstart_time

Cstatus

D"/status"

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong route path

Using wrong variable for uptime calculation

Using incorrect JSON key

The route is '/health', uptime is calculated from start_time, and JSON key is 'status'.

Practice

1. What is the main purpose of a health check endpoint in a Flask application?

easy

A. To connect to the database and run queries

B. To handle user login and authentication

C. To confirm the app is running and responsive

D. To serve static files like images and CSS

Solution

1. Step 1: Understand the role of health check endpoints

   Health check endpoints are simple URLs that return a status message indicating the app is running properly.

2. Step 2: Compare options with this role

   Only To confirm the app is running and responsive matches this purpose. Other options describe unrelated app functions.

3. Final Answer:

   To confirm the app is running and responsive -> Option C

4. Quick Check:

   Health check = Confirm app running [OK]

Hint: Health check endpoints confirm app health quickly [OK]

Common Mistakes:

• Confusing health check with user authentication
• Thinking health check serves static files
• Assuming health check runs database queries

2. Which of the following is the correct way to define a simple health check endpoint in Flask?

easy

A. app.route('/health')
def health():
return {'status': 'ok'}

B. @app.route('/health')
health = {'status': 'ok'}

C. app.route('/health')
health = lambda: {'status': 'ok'}

D. @app.route('/health')
def health():
return {'status': 'ok'}

Solution

1. Step 1: Recall Flask route decorator syntax

   Flask uses @app.route('/path') decorator above a function to define routes.

2. Step 2: Check each option for correct syntax

   @app.route('/health') def health(): return {'status': 'ok'} correctly uses @app.route decorator and defines a function returning a dictionary. Others miss the decorator or define incorrectly.

3. Final Answer:

   @app.route('/health')\ndef health():\n return {'status': 'ok'} -> Option D

4. Quick Check:

   Use @app.route decorator for routes [OK]

Hint: Use @ before app.route to define Flask routes [OK]

Common Mistakes:

• Forgetting the @ symbol before app.route
• Returning a dictionary without a function
• Assigning route to a variable instead of a function

3. Given this Flask code, what will be the JSON response when accessing /health?

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

@app.route('/health')
def health():
    return jsonify(status='ok', uptime=12345)

medium

A. {"status": "ok", "uptime": 12345}

B. status=ok, uptime=12345

C. {"status": ok, "uptime": "12345"}

D. A runtime error occurs

Solution

1. Step 1: Understand jsonify output

   The jsonify function converts keyword arguments into a JSON response with keys as strings and values as their types.

2. Step 2: Check the returned JSON format

   It returns a JSON string with keys "status" and "uptime". The uptime is an integer, so no quotes around 12345.

3. Final Answer:

   {"status": "ok", "uptime": 12345} -> Option A

4. Quick Check:

   jsonify returns JSON string with keys and values [OK]

Hint: jsonify returns proper JSON with quotes on keys and string values [OK]

Common Mistakes:

• Missing quotes around string values
• Confusing Python dict print with JSON string
• Expecting runtime error when code is correct

4. What is wrong with this Flask health check endpoint code?

from flask import Flask
app = Flask(__name__)

app.route('/health')
def health():
    return {'status': 'ok'}

medium

A. The route decorator is missing the @ symbol

B. It will cause a syntax error because return type is wrong

C. It returns a Python dict but Flask needs a Response or JSON

D. The function name 'health' is reserved and cannot be used

Solution

1. Step 1: Recall Flask route decorator syntax

   Flask uses the @app.route('/path') decorator above the function definition. The @ symbol is required to apply the decorator.

2. Step 2: Analyze the provided code

   The code has app.route('/health') without the @, so it calls the route method but does not decorate the health function. Thus, the /health endpoint will not be registered and accessing it returns 404.

3. Final Answer:

   The route decorator is missing the @ symbol -> Option A

4. Quick Check:

   Missing @ means no route registration [OK]

Hint: Use @ before app.route to define Flask routes [OK]

Common Mistakes:

• Returning plain dict without jsonify
• Forgetting @ before route decorator
• Thinking function names are reserved keywords

5. You want to create a health check endpoint in Flask that returns status 'ok' only if the database connection is alive, otherwise 'error'. Which approach is best?

hard

A. Return {'status': 'ok'} always, ignoring database state

B. Check database connection inside the route, return JSON accordingly

C. Use a separate thread to update status and return cached result

D. Raise an exception if database is down and let Flask handle it

Solution

1. Step 1: Understand health check purpose with dependencies

   A health check should verify critical dependencies like database connectivity to report accurate status.

2. Step 2: Evaluate options for checking database state

   Check database connection inside the route, return JSON accordingly directly checks the database connection inside the route and returns JSON status accordingly, which is clear and reliable.

3. Step 3: Consider other options

   Return {'status': 'ok'} always, ignoring database state ignores database state, C adds unnecessary complexity, D relies on exceptions which is less clear for health checks.

4. Final Answer:

   Check database connection inside the route, return JSON accordingly -> Option B

5. Quick Check:

   Health check should verify dependencies live [OK]

Hint: Check dependencies live inside health endpoint for accuracy [OK]

Common Mistakes:

• Ignoring database state in health check
• Overcomplicating with threads or caching
• Relying on exceptions instead of status checks