I just finished watching Why Google Stores Billions of Lines of Code in a Single Repository and honestly, while it looks intriguing, it also looks horrible.
Have you run into issues? Did you love it? How was it/
Thanks for the insight. Are there any tools that you used at your company that you’d recommend? Did you encounter any opensource CICD for monorepos that worked?
I discovered JOSH which was intriguing to put in front of existing source forges, but I don’t know of source forges that support monorepos by design. Github and Gitlab are multirepo for sure and shoehorning a monorepo into that, like nix did with nixpkgs, is cumbersome.
We use them at Meta. It’s easier to interact with other parts of the codebase, but it doesn’t play well with libraries so you end up redoing a lot of stuff in-house.
I would only recommend a monorepo if you’re a company with at least 5,000+ engineers and can dedicate significant time to internal infra.
it doesn’t play well with libraries
What do you mean by that? Is it the versioning of libraries that isn’t possible meaning an update to the interface requires updating all dependent apps/libs?
Updating a library in a monorepo means copying it all over and hoping the lib update didn’t break someone else’s code. Whereas updating a library normally would never break anything, and you can let people update on their own cadence
I set up a monorepo that had a library used by several different projects. It was my first foray into DevOps and we had this problem.
I decided to version and release the library whenever a change was merged to it on the trunk. Other projects would depend on one of those versions and could be updated at their own pace. There was a lot of hidden complexity and many gotchas so we needed some rules to make it functional. It worked good once those were sorted out.
One rule we needed was that changes to the library had to be merged and released prior to any downstream project that relied on those changes. This made a lot of sense from certain perspectives but it was annoying developers. They couldn’t simply open a single PR containing both changes. This had a huge positive impact on the codebase over time IMO but that’s a different story.
How is it done at Meta? Always compile and depend on latest? Is the library copied into different projects, or did you just mean you had to update several projects whenever the library’s interfaces changed?
I would only recommend a monorepo if you’re a company with at least 5,000+ engineers and can dedicate significant time to internal infra.
It’s funny because at least one FANG does not use monorepos and has no problem with them, in spite of being at the same scale or even perhaps larger than Facebook.
I wonder why anyone would feel compelled to suggest adopting a monorepo in a setting that makes them far harder to use and maintain.
Is it Amazon because they did a really good job at keeping teams separate (via APIs)?
Most companies will never have a monorepo at the level of these bigger companies. So I personally don’t think most people need to worry about the limitations of github/lab as platforms.
However if you happen to be having those kinds of issues, I think looking at what the big companies are doing and/or starting to split things up makes sense.
There’s also alternatives with custom ci jobs within non GitHub/lab within the git universe that may help out with those sorts of operations. I know actions still feel very beta in some toolsets so it may be easier/more useful to run your own arch. I’ve been enjoying forgeo/gitea for example, but it’s not like you can’t do the same with girlab runners or GitHub enterprise. Depends on use case.
There’s also alternatives with custom ci jobs within non GitHub/lab within the git universe that may help out with those sorts of operations.
Why would anyone subject themselves to explore nonstandard and improvised solutions to try to fit a usecase that fails to meet your needs to a tool that was not designed to support it?
Do people enjoy creating their own problems just to complain about them?
They work great when you have many teams working alongside each other within the same product.
It helps immensely with having consistent quality, structure, shared code, review practices, CI/CD…etc
The downside is that you essentially need an entire platform engineering team just to set up and maintain the monorepo, tooling, custom scripts, custom workflows…etc that support all the additional needs a monorepo and it’s users have. Something that would never be a problem on a single repository like the list of pull requests maybe something that needs custom processes and workflows for in a monorepo due to the volume of changes.
(Ofc small mono repos don’t require you to have a full team doing maintenance and platform engineering. But often you’ll still find yourself dedicating an entire FTE worth of time towards it)
It’s similar to microservices in that monorepo is a solution to scaling an organizational problem, not a solution to scaling a technology problem. It will create new problems that you have to solve that you would not have had to solve before. And that solution requires additional work to be effective and ergonomic. If those ergonomic and consistency issues aren’t being solved then it will just devolve over time into a mess.
I have no experience using them across an entire company, let alone team. So far, it always seemed good enough to keep just each project in a repo. But yeah, for larger projects consisting out of multiple applications, I would not want to work without a monorepo for that.
Many of the benefits from the video still apply, mainly the consistency in code changes was always useful. You can check out any commit and you’ve got the exact state how everything worked together at the time. No wrangling different versions, no inconsistencies between APIs.
In our build process, we include the Git commit into the applications to have it logged on start-up, so when we get an error report+logs, we can always easily look at the respective code.
But it does depend on your build tooling, if this works well. JVM languages with e.g. Gradle’s multi-project builds are great. Rust’s workspaces are a treat. Python is fucking atrocious with everything we’ve tried (pipenv, poetry, lots of custom scripts+symlinks).
