Production environment configuration in Ruby on Rails - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What is the effect of setting config.cache_classes = true in production?

In a Rails production environment configuration, what does setting config.cache_classes = true do?

A It reloads application classes on every request, slowing down response time.

B It enables verbose logging of class loading for debugging purposes.

C It caches application classes so they are loaded once, improving performance.

D It disables class loading entirely, causing errors when classes are referenced.

💡 Hint

Think about how caching classes affects speed and memory in production.

Setting config.cache_classes = true in production tells Rails to load application classes once and cache them. This avoids reloading classes on every request, which improves performance.

📝 Syntax

intermediate

Identify the correct syntax to enable serving static files in production

Which of the following lines correctly enables serving static files in a Rails production environment configuration file?

A config.public_file_server.enabled = ENV['RAILS_SERVE_STATIC_FILES'].present?

B config.public_file_server.enabled == true

C config.public_file_server.enabled = true if ENV['RAILS_SERVE_STATIC_FILES']

D config.public_file_server.enabled = ENV['RAILS_SERVE_STATIC_FILES']

💡 Hint

Check how to properly assign a boolean based on environment variable presence.

The correct syntax uses ENV['RAILS_SERVE_STATIC_FILES'].present? to check if the environment variable is set and assigns a boolean accordingly.

❓ state_output

advanced

What is the value of config.log_level after this production config runs?

Given this snippet in config/environments/production.rb:

Rails.application.configure do
  config.log_level = :info
  config.log_level = :debug if ENV['DEBUG_LOG'] == 'true'
end

If the environment variable DEBUG_LOG is not set, what is the final value of config.log_level?

A :debug

B :info

C nil

D Raises an error because ENV['DEBUG_LOG'] is nil

💡 Hint

Consider what happens when the environment variable is missing.

If ENV['DEBUG_LOG'] is not set, the condition ENV['DEBUG_LOG'] == 'true' is false, so config.log_level remains :info.

🔧 Debug

advanced

Why does this production config cause an error?

Examine this production environment configuration snippet:

Rails.application.configure do
  config.action_mailer.raise_delivery_errors = true
  config.action_mailer.delivery_method = :smtp
  config.action_mailer.smtp_settings = {
    address: 'smtp.example.com',
    port: 587,
    domain: 'example.com',
    user_name: ENV['SMTP_USER'],
    password: ENV['SMTP_PASS'],
    authentication: 'plain',
    enable_starttls_auto: true
  }
end

Why does this code raise a syntax error?

A Missing commas between some hash key-value pairs cause a syntax error.

B Using symbols as keys in smtp_settings is not allowed in production config.

C The delivery_method :smtp is invalid in production environment.

D ENV variables cannot be used directly in production config files.

💡 Hint

Look carefully at punctuation between hash entries.

In Ruby hashes, commas are required between key-value pairs. Missing commas after address: 'smtp.example.com' and domain: 'example.com' cause syntax errors.

🧠 Conceptual

expert

Which production config setting ensures assets are precompiled and digest filenames are used?

In Rails production configuration, which setting ensures that assets are precompiled and served with digest fingerprints for caching?

A config.assets.precompile = false

B config.assets.compile = true

C config.assets.debug = true

D config.assets.digest = true

💡 Hint

Think about how Rails manages asset filenames for caching in production.

config.assets.digest = true enables fingerprinting of asset filenames, which helps browsers cache assets effectively. This is standard in production.

Practice

1. What is the main purpose of the production.rb file in a Rails application?

easy

A. To define routes for the application

B. To enable detailed error messages for debugging

C. To configure settings that optimize the app for real users, like caching and security

D. To set up the database schema

Solution

1. Step 1: Understand the role of production.rb

   This file holds configuration settings specifically for the production environment, where the app serves real users.

2. Step 2: Identify key production settings

   It disables detailed error messages and enables caching to improve speed and security.

3. Final Answer:

   To configure settings that optimize the app for real users, like caching and security -> Option C

4. Quick Check:

   Production config = optimize for real users [OK]

Hint: Production config = speed + security settings [OK]

Common Mistakes:

• Confusing production with development environment
• Thinking production shows detailed errors
• Mixing routing or database setup with production config

2. Which line correctly disables full error reports in config/environments/production.rb?

easy

A. config.consider_all_requests_local = false

B. config.show_detailed_errors = true

C. config.consider_all_requests_local = true

D. config.show_detailed_errors = false

Solution

1. Step 1: Identify the setting for error reports

   The setting consider_all_requests_local controls whether detailed error pages show.

2. Step 2: Know production default

   In production, this is set to false to hide detailed errors from users.

3. Final Answer:

   config.consider_all_requests_local = false -> Option A

4. Quick Check:

   Disable detailed errors = false [OK]

Hint: False hides errors in production [OK]

Common Mistakes:

• Setting it to true shows errors in production
• Using wrong config key like show_detailed_errors
• Confusing development and production defaults

3. Given this snippet in production.rb:

config.cache_classes = true
config.action_controller.perform_caching = true
config.assets.compile = false

What happens if you deploy without precompiling assets?

medium

A. The app will crash with a syntax error

B. Rails will compile assets on the fly, slowing down requests

C. Assets will be served normally from the public folder

D. Assets will not be served, causing missing styles and scripts

Solution

1. Step 1: Understand config.assets.compile = false

   This setting disables on-the-fly asset compilation in production.

2. Step 2: Consequence of no precompiled assets

   If assets are not precompiled, Rails cannot serve them, so styles and scripts will be missing.

3. Final Answer:

   Assets will not be served, causing missing styles and scripts -> Option D

4. Quick Check:

   No precompile + compile false = missing assets [OK]

Hint: No precompile + compile false = missing assets [OK]

Common Mistakes:

• Assuming Rails compiles assets automatically in production
• Thinking assets serve normally without precompile
• Confusing compile false with true

4. You see this error in production: ActionController::RoutingError (No route matches [GET] "/assets/application.css"). Which fix is correct?

medium

A. Precompile assets before deploying and keep config.assets.compile = false

B. Set config.assets.compile = true in production.rb

C. Remove caching settings from production.rb

D. Set config.consider_all_requests_local = true

Solution

1. Step 1: Understand the error cause

   The error means the CSS asset is missing in production, likely because assets were not precompiled.

2. Step 2: Correct fix for missing assets

   Best practice is to precompile assets before deployment and keep config.assets.compile = false for performance.

3. Final Answer:

   Precompile assets before deploying and keep config.assets.compile = false -> Option A

4. Quick Check:

   Missing assets fix = precompile + compile false [OK]

Hint: Always precompile assets for production [OK]

Common Mistakes:

• Setting compile true causes slow requests
• Removing caching does not fix missing assets
• Enabling detailed errors leaks info in production

5. You want to securely configure your Rails app for production to use environment variables for secrets and enable caching. Which combination in production.rb is best practice?

hard

A. config.cache_classes = false
config.action_controller.perform_caching = false
config.secret_key_base = ENV['SECRET_KEY_BASE']

B. config.cache_classes = true
config.action_controller.perform_caching = true
config.secret_key_base = ENV['SECRET_KEY_BASE']

C. config.cache_classes = true
config.action_controller.perform_caching = false
config.secret_key_base = 'hardcoded_secret'

D. config.cache_classes = false
config.action_controller.perform_caching = true
config.secret_key_base = 'hardcoded_secret'

Solution

1. Step 1: Identify caching and class loading best practices

   In production, cache_classes and perform_caching should be true for speed and efficiency.

2. Step 2: Use environment variables for secrets

   Secrets like secret_key_base must come from environment variables, not hardcoded strings, for security.

3. Final Answer:

   config.cache_classes = true config.action_controller.perform_caching = true config.secret_key_base = ENV['SECRET_KEY_BASE'] -> Option B

4. Quick Check:

   Caching true + env secrets = secure production [OK]

Hint: Cache true + env secrets = secure production [OK]

Common Mistakes:

• Disabling caching in production
• Hardcoding secret keys in code
• Setting cache_classes false reduces performance