Why We Use Ruby on Rails to Build GitLab

When our Co-founder and Engineering Fellow Dmitriy Zaporozhets decided to build GitLab, he chose to do it with Ruby on Rails, despite working primarily in PHP at the time. GitHub, a source of inspiration for GitLab, was also based on Rails, making it a logical pick considering his interest in the framework. GitLab CEO Sid Sijbrandij thinks his co-founder made a good choice:

"It's worked out really well because the Ruby on Rails ecosystem allows you to shape a lot of functionality at a high quality," he explained. "If you look at GitLab, it has an enormous amount of functionality. Software development is very complex and to help with that, we need a lot of functionality and Ruby on Rails is a way to do it. Because there's all these best practices that are on your happy path, it's also a way to keep the code consistent when you ship something like GitLab. You're kind of guided into doing the right thing."

Depending on Useful Gems

Ruby gems play an integral role in the building of GitLab, with it loading more than a thousand non-unique gems, according to Sid. Calling the Ruby on Rails framework "very opinionated," he thinks it's a strong environment in which to build a complex app like GitLab.

"There's a great ecosystem around it with gems that can make assumptions about how you're doing things and in that regard, I think the Ruby on Rails ecosystem is still without par," he says. "If you look at our Gemfile, it gives you an indication of how big the tower is of dependencies that we can build on. Ruby on Rails has amazing shoulders to stand on and it would have been much slower to develop GitLab in any other framework."

Overcoming Challenges

All of this is not to say there haven't been challenges in building GitLab with Ruby on Rails. Performance has been an issue that our developers have made strides to improve in a number of ways, including rewriting code in Go and using the Vue framework. The latter is being used to rewrite frequently accessed pages, like issues and merge requests, so they load faster, improving user experience.

Go is being used to address other issues affecting load times and reduce memory usage.

"Ruby was optimized for the developer, not for running it in production," says Sid. "For the things that get hit a lot and have to be very performant or that, for example, have to wait very long on a system IO, we rewrite those in Go ... We are still trying to make GitLab use less memory. So, we'll need to enable multithreading. When we developed GitLab that was not common in the Ruby on Rails ecosystem. Now it's more common, but because we now have so much code and so many dependencies, it's going to be a longer path for us to get there. That should help; it won't make it blazingly fast, but at least it will use less memory."

Adding Go to GitLab's toolbox led to the creation of a separate service called Gitaly, which handles all Git requests.

Building on GitLab's Mission

The organized, structured style of Ruby on Rails' framework falls in line with our core mission. Because Rails is streamlined, anyone can jump into GitLab and participate, which made it especially attractive to Sid from the start.

"Our mission is that everyone can contribute," he explains. "Because Ruby on Rails is really opinionated about which pieces go where, it's much easier for new developers to get into the codebase, because you know where people have put stuff. For example, in every kitchen you enter, you never know where the knives and plates are located. But with Ruby on Rails, you enter the kitchen and it's always in the same place, and we want to stick to that.

In every kitchen you enter, you never know where the knives and plates are located. But with Ruby on Rails, you enter the kitchen and it's always in the same place, and we want to stick to that.

"I was really encouraged when I opened the project and saw it for the first time a year after Dmitriy started it. I opened it up and it's idiomatic Rails. He followed all the principles. He didn't try to experiment with some kind of fad that he was interested in. He made it into a production application. Dmitriy carefully vetted all the contributions to make sure they stick to those conventions, and that's still the case. I think we have a very nice codebase that allows other people to build on top of it. One of our sub-values is boring solutions: don't do anything fancy. This is so that others can build on top it. I think we've done that really well ... and we're really thankful that Ruby has been such a stable ecosystem for us to build on."