Question 1

How do I set up Motorhead for A/B testing in a Rails app?

Accepted Answer

Use Motorhead's conditional execution with Ruby Procs to dynamically enable engines based on user segments, and isolate variant logic in separate engines. You can extend controllers or overwrite views to implement different experiences, similar to traditional A/B testing but with engine isolation.

Question 2

Motorhead vs Flipper: which is better for Rails feature toggles?

Accepted Answer

Motorhead is better for encapsulating entire features in isolated engines for parallel development and safe rollouts, while Flipper is a lightweight feature flag library focused on simple toggle management. Choose Motorhead if you need full MVC isolation; opt for Flipper for straightforward flagging without engine overhead.

Question 3

Can Motorhead handle database migrations for new features?

Accepted Answer

No, Motorhead currently does not support model extension or built-in database migration handling, as noted in its todo list. You'll need to manage migrations separately in the main application, which can complicate feature isolation.

Question 4

How to disable a Motorhead engine in production without downtime?

Accepted Answer

Use the RoadCrew admin console to dynamically disable engines via the UI, or configure the engine's active_if Proc to return false based on conditions. This allows instant rollback without code deployment, leveraging Motorhead's error-proof design.

Question 5

What are the performance implications of using multiple Motorhead engines?

Accepted Answer

Each engine adds routing and middleware overhead, which can impact request processing time, especially with many active engines. However, the conditional execution helps mitigate this by only loading engines when needed, but it's still more resource-intensive than simpler flag systems.

Question 6

How to extend an existing Rails controller with Motorhead?

Accepted Answer

Generate a controller in a Motorhead engine that inherits from the main app's controller, override actions, and use super to call the original logic. This allows adding new functionality while preserving existing behavior, as demonstrated in the README examples.

Motorhead

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