Frequently Asked Questions

Some frequently asked questions.

I made a ball of mud :( Should I feel bad?

No, not really. When exploring new terrain it’s hard to do all the thinking beforehand. Usually you don’t even know where to draw the bounded contexts in your app from the start. Only after a while it becomes more evident what stays. Martin Fowler writes more about it in MonolithFirst

Is Rails bad?

No rails isn’t bad, rails is awesome. It allows you to go fast and deliver at breakneck speed. And probably if you have these problems you’re already pretty successful. This is just a guide when you got to a point when you want to break up your monolith into a modular monolith. Or make you aware that there are different patterns that you can employ to prevent this.

What are the implications of a big ball of mud?

• Hard to replace parts of the application.
• Hard to test parts in isolation.
• Lot of cognetive strain since the code touches big parts of the codebase.

Where do you put the engines?

I put the engines in the same folder as the rest of the rails repo. Directly in the root folder. Decidem has a good example on how to do this. Some people put them in an engines/ folder like Flexport.

How do you enforce boundaries between engines?

You can use rubocop to make sure engineers don’t accidently cross the boundaries. Flexport has build a gem for this to keep the boundaries in check.

Monorepo or multirepo?

Monorepo, its much easier to make changes across the app if you need to.

How do we deploy?

Just deploy like you always do! Its the same rails application.

How do we test?

You just test your engine in isolation. And the depending engines that might break. Dan Manges has a pretty good article about it on how to test only the affected engines.

How do we communicate between engines?

Most resources seem to point out to a certain event based approach like observer or pubsub pattern. Flexport uses a pubsub approach. Dan from Root uses events and also discusses this in his article.

How does one work in teams?

You can assign dedicated teams dedicated bounded contexts or engines.