Introduction

Error handling in Ruby on Rails is a critical component of building stable and maintainable applications. Poorly managed errors can lead to security risks, application crashes, and poor user experience.

In this guide, we will cover:
✔️ How Rails handles exceptions by default
✔️ Custom exception handling for improved debugging
✔️ Centralized error management
✔️ Best practices for logging and monitoring
✔️ Using third-party tools for error tracking

By mastering these techniques, you can ensure better fault tolerance, improved debugging, and a seamless user experience. 🚀

1. Understanding Rails’ Default Error Handling

Rails uses middleware-based error handling, primarily via `ActionDispatch::ShowExceptions`.

By default:

  • In development, Rails shows a detailed error page with stack traces.
  • In production, Rails renders generic error pages (500, 404, etc.) to prevent exposing sensitive information.
Customizing Default Error Pages

You can override Rails’ default error pages by adding custom views:

app/views/errors/404.html.erb  
app/views/errors/500.html.erb

Next, configure your routes:

match "/404", to: "errors#not_found", via: :all  
match "/500", to: "errors#internal_server_error", via: :all

2. Using Custom Exceptions in Rails

For better control over errors, create custom exception classes.

Step 1: Define a Custom Exception Class

Create a new file in `app/exceptions/`:

class PaymentProcessingError < StandardError; end
Step 2: Raise Custom Exceptions in Code
def process_payment  
raise PaymentProcessingError, "Payment service unavailable" unless payment_service_available?  
end
Step 3: Handle Custom Exceptions in Controllers
rescue_from PaymentProcessingError, with: :handle_payment_error

def handle_payment_error(exception)  
render json: { error: exception.message }, status: :service_unavailable  
end

3. Centralized Error Handling in ApplicationController

Instead of handling errors in every controller, centralize error management in `ApplicationController`.

class ApplicationController < ActionController::API  
rescue_from ActiveRecord::RecordNotFound, with: :record_not_found  
rescue_from PaymentProcessingError, with: :payment_error

private

def record_not_found(exception)  
render json: { error: "Record not found: #{exception.message}" }, status: :not_found  
end

def payment_error(exception)  
render json: { error: exception.message }, status: :unprocessable_entity  
end  
end

4. Logging and Monitoring Errors

Proper logging helps debug issues faster.

Best Practices for Logging:

✔️ Use Rails’ built-in logging via `Rails.logger`
✔️ Capture request details and user context
✔️ Send logs to external monitoring services

Example:

Rails.logger.error("Payment failed for user #{current_user.id}: #{exception.message}")
Using External Monitoring Tools

Popular error tracking services:

  • Sentry (`sentry-ruby`)
  • Rollbar (`rollbar`)
  • Airbrake (`airbrake`)

Example Sentry Integration:

Sentry.capture_exception(exception)

5. Handling Background Job Failures

For jobs using Sidekiq, Delayed Job, or Resque, wrap execution in a rescue block and log errors.

class MyWorker  
include Sidekiq::Worker

def perform  
do_some_work  
rescue StandardError => e  
Rails.logger.error("Background job failed: #{e.message}")  
raise e  
end  
end

6. Secure Exception Handling

To prevent leaking sensitive data:
🚫 Don’t expose full stack traces in production
✅ Use generic error messages for users
✅ Log detailed errors only in secure logs

Example:

rescue_from StandardError do |exception|  
Rails.logger.error("Unhandled exception: #{exception.message}")  
render json: { error: "Something went wrong. Please try again." }, status: :internal_server_error  
end

Conclusion

Mastering error handling in Rails improves application stability, security, and debugging efficiency. By implementing custom exceptions, centralized error management, logging, and monitoring, you can build robust and fault-tolerant applications.

🚀 Next Steps:
🔹 Integrate an error tracking system
🔹 Improve logging and observability
🔹 Securely handle user-facing error messages

For more Rails best practices, check out our latest guides!