Rate limiting in Ruby on Rails - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to set a rate limit of 5 requests per minute using Rack::Attack.

Ruby on Rails

Rack::Attack.throttle('req/ip', limit: 5, period: 60) do |req|
  req.[1]
end

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

Auser_agent

Bpath

Chost

Dip

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'path' instead of 'ip' will limit requests per URL, not per user.

Using 'user_agent' is not reliable for identifying unique users.

The ip method returns the client's IP address, which is commonly used to identify unique requesters for rate limiting.

2fill in blank

medium

Complete the code to block requests from a specific IP address '192.168.1.1'.

Ruby on Rails

Rack::Attack.blocklist('block 192.168.1.1') do |req|
  req.[1] == '192.168.1.1'
end

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

Apath

Buser_agent

Cip

Dhost

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'user_agent' will not block by IP.

Using 'path' or 'host' will not correctly identify the IP.

The ip method returns the IP address of the request, which you compare to the blocked IP.

3fill in blank

hard

Fix the error in the throttle block to correctly count requests per user ID.

Ruby on Rails

Rack::Attack.throttle('req/user', limit: 10, period: 60) do |req|
  req.env['warden'].user.[1]
end

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

Aname

Bid

Cemail

Dsession

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'name' or 'email' may not be unique or always present.

Using 'session' is not a user attribute.

The id uniquely identifies the user, which is needed to count requests per user.

4fill in blank

hard

Fill both blanks to create a custom response for throttled requests with status 429 and a JSON message.

Ruby on Rails

Rack::Attack.throttled_response = lambda do |env|
  [[1], { 'Content-Type' => 'application/json' }, [{ error: [2] }.to_json]]
end

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

A429

B"Too many requests"

C"Request limit exceeded"

D403

Attempts:

3 left

💡 Hint

Common Mistakes

Using 403 instead of 429 is incorrect for rate limiting.

Not using a string message in JSON causes errors.

Status code 429 means too many requests. The JSON message should explain the error clearly.

5fill in blank

hard

Fill all three blanks to define a throttle that limits POST requests to '/login' to 5 per minute per IP.

Ruby on Rails

Rack::Attack.throttle('logins/ip', limit: [1], period: [2]) do |req|
  req.[3] if req.path == '/login' && req.post?
end

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

A5

B60

Cip

Duser_agent

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'user_agent' instead of 'ip' will not limit per user IP.

Setting the wrong period or limit changes the throttle behavior.

The limit is 5 requests, period is 60 seconds (1 minute), and the IP address identifies the user.

Practice

1. What is the main purpose of rate limiting in a Rails application?

easy

A. To control how often users can make requests to the server

B. To speed up database queries automatically

C. To style the user interface dynamically

D. To manage user sessions securely

Solution

1. Step 1: Understand rate limiting concept

   Rate limiting is about controlling the number of requests a user can make in a time period.

2. Step 2: Identify the main purpose in Rails context

   It helps protect the server from overload and abuse by limiting request frequency.

3. Final Answer:

   To control how often users can make requests to the server -> Option A

4. Quick Check:

   Rate limiting = controlling request frequency [OK]

Hint: Rate limiting controls request frequency to protect servers [OK]

Common Mistakes:

• Confusing rate limiting with UI styling
• Thinking it speeds up database queries
• Mixing it with session management

2. Which of the following is the correct way to configure a simple rate limit using Rack::Attack in Rails?

easy

A. Rack::Attack.throttle('req/ip', limit: 5, period: 1.minute) { |req| req.ip }

B. Rack::Attack.limit('req/ip', 5, 1.minute) { |req| req.ip }

C. Rack::Attack.throttle('req/ip', 1.minute, limit: 5) { |req| req.ip }

D. Rack::Attack.block('req/ip', limit: 5, period: 1.minute) { |req| req.ip }

Solution

1. Step 1: Recall Rack::Attack throttle syntax

   The correct method is throttle with arguments: name, limit, period, and a block returning the key.

2. Step 2: Match syntax with options

   Rack::Attack.throttle('req/ip', limit: 5, period: 1.minute) { |req| req.ip } uses throttle with named parameters limit: 5 and period: 1.minute, and block returning req.ip, which is correct.

3. Final Answer:

   Rack::Attack.throttle('req/ip', limit: 5, period: 1.minute) { |req| req.ip } -> Option A

4. Quick Check:

   Correct method and parameters = Rack::Attack.throttle('req/ip', limit: 5, period: 1.minute) { |req| req.ip } [OK]

Hint: Use throttle with named limit and period parameters [OK]

Common Mistakes:

• Using wrong method name like limit or block
• Swapping limit and period order
• Not passing a block returning the key

3. Given this Rack::Attack throttle configuration:

Rack::Attack.throttle('logins/ip', limit: 3, period: 20.seconds) { |req| req.ip if req.path == '/login' && req.post? }

What happens if a user makes 4 POST requests to '/login' within 20 seconds from the same IP?

medium

A. Only the 1st request is blocked

B. The 4th request is blocked due to rate limit

C. All 4 requests are allowed without restriction

D. The 4th request resets the limit counter

Solution

1. Step 1: Understand throttle parameters

   The limit is 3 requests per 20 seconds per IP for POST requests to '/login'.

2. Step 2: Analyze 4 POST requests from same IP

   The first 3 requests pass, the 4th exceeds the limit and is blocked.

3. Final Answer:

   The 4th request is blocked due to rate limit -> Option B

4. Quick Check:

   Requests > limit = block excess [OK]

Hint: Requests over limit within period get blocked [OK]

Common Mistakes:

• Assuming all requests pass
• Thinking limit resets on 4th request
• Confusing which requests count

4. You wrote this code to limit API requests:

Rack::Attack.throttle('api/ip', limit: 10, period: 1.minute) do |req|
  req.ip if req.path.start_with?('/api')
end

But users report no limits are applied. What is the likely problem?

medium

A. The period should be in seconds, not minutes

B. The limit value 10 is too high to trigger blocking

C. The block returns nil for non-API paths, so no key is generated for those requests

D. The method throttle is not supported in Rack::Attack

Solution

1. Step 1: Check block return value logic

   The block returns req.ip only if path starts with '/api', else returns nil.

2. Step 2: Understand throttle key generation

   If block returns nil, no key is generated and no limit applies for those requests.

3. Final Answer:

   The block returns nil for non-API paths, so no key is generated for those requests -> Option C

4. Quick Check:

   Nil key means no rate limiting applied [OK]

Hint: Block must return key for all requests to apply limits [OK]

Common Mistakes:

• Thinking limit 10 is too high
• Confusing period units
• Believing throttle method is unsupported

5. You want to limit login attempts per user email and IP address separately using Rack::Attack. Which configuration correctly applies this?

hard

A. Rack::Attack.throttle('logins/email', limit: 5, period: 1.hour) { |req| req.params['email'].presence }Rack::Attack.throttle('logins/ip', limit: 10, period: 1.hour) { |req| req.params['email'] }

B. Rack::Attack.throttle('logins/email_ip', limit: 5, period: 1.hour) { |req| req.params['email'] + req.ip }

C. Rack::Attack.throttle('logins/email', limit: 5, period: 1.hour) { |req| req.ip }Rack::Attack.throttle('logins/ip', limit: 10, period: 1.hour) { |req| req.params['email'] }

D. Rack::Attack.throttle('logins/email', limit: 5, period: 1.hour) { |req| req.params['email'] }Rack::Attack.throttle('logins/ip', limit: 10, period: 1.hour) { |req| req.ip }

Solution

1. Step 1: Understand separate throttles for email and IP

   We want one throttle keyed by email, another keyed by IP address.

2. Step 2: Match keys to correct throttle names

   Rack::Attack.throttle('logins/email', limit: 5, period: 1.hour) { |req| req.params['email'] }
   Rack::Attack.throttle('logins/ip', limit: 10, period: 1.hour) { |req| req.ip } correctly uses req.params['email'] for email throttle and req.ip for IP throttle with proper limits.

3. Final Answer:

   Rack::Attack.throttle('logins/email', limit: 5, period: 1.hour) { |req| req.params['email'] }
   Rack::Attack.throttle('logins/ip', limit: 10, period: 1.hour) { |req| req.ip } -> Option D

4. Quick Check:

   Separate keys for email and IP = Rack::Attack.throttle('logins/email', limit: 5, period: 1.hour) { |req| req.params['email'] }
   Rack::Attack.throttle('logins/ip', limit: 10, period: 1.hour) { |req| req.ip } [OK]

Hint: Use separate throttle blocks keyed by email and IP [OK]

Common Mistakes:

• Mixing email and IP keys in wrong throttles
• Concatenating email and IP as one key
• Using IP where email key is needed