> if updating that shared library automatically updates everyone and isn’t backward compatible you’re doing it wrong that library should be published as a v2 or dependents should pin to a specific version

...but why? You're begging the question.

If you can automatically update everyone including running their tests and making any necessary changes to their code, then persisting two versions forever is a waste of time. If it's because you can't be certain from testing that it's actually a safe change, then fine, but note that that option is still available to you by copy/pasting to a v2/ or adding a feature flag. Going to a monorepo gives you strictly more options in how to deal with changes.

> You literally wouldn’t be able to keep track of your BOM in version control as it obtains a time component based on when you built the service

This is true regardless of deployment pattern. The artifact that you publish needs to have pointers back to all changes that went into it/what commit it was built at. Mono vs. multi-repo doesn't materially change that, although I would argue it's slightly easier with a monorepo since you can look at the single history of the repository, rather than having to go an extra hop to find out what version 1.0.837 of your dependency included.

> the version that was published in the registry

Maybe I'm misunderstanding what you're getting at, but monorepo dependencies typically don't have a registry - you just have the commit history. If a binary is built at commit X, then all commits before X across all dependencies are included. That's kind of the point.

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vlovich123 3 hours ago | parent [-]

> ...but why? You're begging the question. If you can automatically update everyone including running their tests and making any necessary changes to their code, then persisting two versions forever is a waste of time.

I’m not begging the question. I’m simply stating what loose coupling looks like and the blog post is precisely the problem of tight coupling. If you have multiple teams working on a tightly coupled system you’re asking for trouble. This is why software projects inevitably decompose against team boundaries and you ship your org chart - communication and complexity is really hard to manage as the head count grows which is where loose coupling helps.

But this article isn’t about moving from federated codebases to a single monorepo as you propose. They used that as an intermediary step to then enable making it a single service. But the point is that making a single giant service is well studied and a problem. Had this constantly at Apple when I worked on CoreLocation where locationd was a single service that was responsible for so many things (GPS, time synchronization of Apple Watches, WiFi location, motion, etc) that there was an entire team managing the process of getting everything to work correctly within a single service and even still people constantly stepped on each other’s toes accidentally and caused builds that were not suitable. It was a mess and the team that should have identified it as a bottleneck in need of solving (ie splitting out separate loosely coupled services) instead just kept rearranging deck chairs.

> Maybe I'm misunderstanding what you're getting at, but monorepo dependencies typically don't have a registry - you just have the commit history

I’m not opposed to a monorepo which I think may be where your confusion is coming from. I’m suggesting slamming a bunch of microservices back together is a poorly thought out idea because you’ll still end up with a launch coordination bottleneck and rolling back 1 team’s work forces other teams to roll back as well. It’s great the person in charge got to write a ra ra blog post for their promo packet. Come talk to me in 3 years with actual on the ground engineers saying they are having no difficulty shipping a large tightly coupled monolithic service or that they haven’t had to build out a team to help architect a service where all the different teams can safely and correctly coexist. My point about the registry is that they took one problem - a shared library multiple services depend on through a registry depend on latest causing problems deploying - and nuked it from orbit using a monorepo (ok - this is fine and a good solution - I can be a fan of monorepos provided your infrastructure can make it work) and making a monolithic service (probably not a good idea that only sounds good when you’re looking for things to do).

	▲	necovek 2 hours ago \| parent [-]
		> I’m not begging the question. I’m simply stating what loose coupling looks like and the blog post is precisely the problem of tight coupling. But it is not! They were updating dependencies and deploying services separately, and this led to every one of 140 services using a different version of "shared-foo". This made it cumbersome, confusing and expensive to keep going (you want a new feature from shared-foo, you have to take all the other features unless you fork and cherrypick on top, which makes it a not shared-foo anymore). The point is that true microservice approach will always lead to exactly this situation: a) you either do not extract shared functions and live with duplicate implementations, b) you enforce keeping your shared dependencies always on very-close-to-latest (which you can do with different strategies; monorepo is one that enables but does not require it) or c) you end up with a mess of versions being used by each individual service. The most common middle ground is to insist on backwards compatibility in a shared-lib, but carrying that over 5+ years is... expensive. You can mix it with an "enforce update" approach ("no version older than 2 years can be used"), but all the problems are pretty evident and expected with any approach. I'd always err on the side of having a capability to upgrade at once if needed, while keeping the ability to keep a single service on a pinned version. This is usually not too hard with any approach, though monorepo makes the first one appear easier (you edit one file, or multiple dep files in a single repo): but unless you can guarantee all services get replaced in a deployment at exactly the same moment — which you rarely can — or can accept short lived inconsistencies, deployment requires all services to be backwards compatible until they are all updated with either approach). I'd also say that this is still not a move to a monolith, but to a Service-Oriented-Architecture that is not microservices (as microservices are also SOA): as usual, the middle ground is the sweet spot.