How to Seamlessly Upgrade Your Ruby on Rails Application: A Step-by-Step Recipe

Upgrading a Ruby on Rails application can feel daunting, especially when dealing with gem dependencies, breaking changes, and ensuring your production environment remains stable. However, with careful planning and the right steps, the process can be managed efficiently.

In this guide, I’ll walk you through a tried-and-tested approach to upgrading Rails, highlighting the common challenges, essential tools, and lessons learned from practical upgrades.

Challenges and Risks in Upgrading Ruby on Rails

When upgrading Ruby on Rails, one of the biggest challenges is dealing with outdated gems that block the Rails upgrade due to conflicting interdependencies. For instance, Rails might require a version constraint on a gem like Nokogiri (e.g., > 3), while an outdated gem still depends on Nokogiri = 2. This kind of conflict can prevent the upgrade unless all dependent gems are updated as well.

Another major challenge is the breaking changes that are not well-documented. Even with Rails' excellent upgrade guides, some changes only surface through testing or—worse—after deployment to production.

The risks come primarily from these breaking changes that might not be caught during development or continuous integration (CI) testing and only show up when the application is live in production.

Your Rails Upgrade Checklist

Before starting the upgrade process, it's important to follow a structured checklist to ensure everything is in place. Here’s a reliable process I recommend:

Update All Gems:
Before even touching Rails, ensure that all your gems are up to date. This helps reduce conflicts with dependencies later. After upgrading, test and deploy to confirm stability.
Check for the Latest Rails Patch Version:
Start by checking if your current version of Rails has a latest patch release (e.g., from Rails 6.0.x to 6.0.y). Often, patch versions introduce deprecation warnings that help prepare for the next minor or major version upgrade.
Resolve Deprecation Warnings:
Deprecation warnings are your best friend in this process. Use tools like the next_rails gem to detect and list all deprecation warnings during test runs. Resolving these warnings early is critical for a smoother upgrade.
Upgrade Rails Gem:
Once you're ready, upgrade the Rails gem using the bundle update command. This will update your Gemfile.lock and ensure you have the latest Rails version.
Run the Rails Update Command:
Rails provides the rails app:update command after upgrading. This command offers an interactive session to help you create new files and update old ones, making sure your app is in sync with the new Rails version.

Tools and Methods to Streamline the Upgrade Process

The key to a smooth upgrade lies in your testing setup. Here are some essential steps:

Comprehensive Test Coverage:
Ensure you have a solid test suite with high coverage before starting the upgrade. This way, you can easily catch regressions and issues caused by breaking changes.
CI/CD Setup:
Use CI/CD pipelines to automatically run tests and flag any deprecated methods or APIs before upgrading. This continuous feedback loop helps keep your codebase clean and stable.
Observability Tools:
Utilize tools like Datadog, Honeybadger, and New Relic to monitor logs for errors related to the upgrade. These observability platforms help track any anomalies, performance degradation, or errors that may surface after the upgrade, giving you insight into how your application behaves in real-time.
Version Control:
Always ensure your version control strategy is solid. Create feature branches for the upgrade and test each step thoroughly before merging into your main branch.

Managing Dependencies and Gem Compatibility

Before attempting a Rails upgrade, ensure that all outdated gems are upgraded to their latest versions. This reduces the chance of dependency conflicts during the upgrade.

Once the upgrade begins, test compatibility with essential gems like Devise, Nokogiri, or Sidekiq to ensure they work seamlessly with the new Rails version.

Handling Breaking Changes and Deprecated Features

The best approach is to resolve deprecated features before the upgrade. Rails’ patch versions often introduce backward-compatible deprecation warnings that prepare you for the next minor or major version. Use this to your advantage by cleaning up your codebase ahead of time.

After upgrading, run both automated tests and manual tests to ensure that everything is functioning correctly.

Lessons Learned from Practical Upgrades

Here are some key takeaways from my experience upgrading Rails:

Breaking Changes Aren’t Always Documented:
Not all breaking changes are listed in the official Rails upgrade guide. Some arise due to dependencies or indirect effects of the upgrade. Having comprehensive tests in place is the best defense against these.
Testing Beyond Development Environments:
Don’t rely solely on local or development environment testing. Use staging or preview environments that closely resemble production. Pay attention to logs and monitoring tools to catch issues that may be missed in dev, such as caching and asset management discrepancies.
Consistent Configuration Across Environments:
Ensure that your staging, sandbox, and production environments have similar configurations. A mismatch between these environments can lead to false positives or negatives during testing, making your staging environment unreliable.

Conclusion

Upgrading Ruby on Rails can be a smooth process with the right preparation and tools. By following this structured recipe—updating dependencies, resolving deprecations, testing thoroughly, and using the proper tools—you can confidently upgrade your application with minimal risk.

Remember, testing is key. Stay vigilant, monitor closely, and ensure your environments are consistent to avoid surprises in production.