16 ms·

Monorepo is great if you're really good

225 points by mr_crankypants 7y ago

dmitriz 7y ago
> like Google, the ultimate force for Good in technology Hahaha... https://www.reddit.com/r/degoogle/ https://www.reddit.com/r/degoogle/ https://twitter.com/hashtag/degoogle https://twitter.com/hashtag/degoogle
dmitriz 7y ago
> What do you do when you have a branch working on Android and another branch working on iOS and you have deliveries on both platforms? Stop it and focus on one single web app instead that anyone can run. Unless your app is going to be in the top 10 that people can't miss downloading.
rezmason 7y ago
Ask your doctor if Monorepo is right for you.
- ghostbrainalpha 7y ago
  Individual results may vary. Don't take Monorepo if you are bad at programming, or if you may become bad at programming. Side effects include but are not limited to your repo growing into a single giant ball of circular dependencies.
  - newshorts 7y ago
    Monorepo may cause blindness, sleep deprivation and suicidal thoughts. If you experience any of these symptoms, stop taking monorepo and consult your manager.
    - asark 7y ago
      If you experience a build lasting more than six hours, seek rockstar ninja help immediately.
- vidanay 7y ago
  Ask not what your monorepo can do for you - ask what you can do for your monorepo.
- asdfman123 7y ago
  In the real world, it doesn't work that way. In the real world you ask your doctor if it's okay and he says "sure" because he's read a few things about it and it's what you seem to want. But he doesn't really know, because no one is capable of understanding the human body in its full complexity. So you just end up taking Monorepo and hoping it doesn't make you severely depressed or give you seizures that send you to the emergency room.
cbanek 7y ago
> the entire code base got forked, and the entire org is now held hostage by the dumbass. > Of course in a Good team, needless dependencies would be weeded out in code reviews, and a Culture would evolve over time avoiding needless dependencies. Really, the one consistent thing is that if you have a good team, you'll make it work no matter what tech or decisions you make (assuming you're also good enough to know when you've lost and change course), and if you're a bad team, you're doomed to failure, because, well, you're bad (by definition). I think this article also vastly underestimates the cost and annoyance of the tooling of CI'ing a large number of repos, especially if you have to match or do some kind of cross product on the feature branches. (such as, repo A branch B can only be built with repo C branch F, but all the other repos should be master)
- humbleMouse 7y ago
  Umm, appoint someone or a trusted few as git admins and only allow them to merge commits? (responding to the article contents quoted in above comment)
  - grenoire 7y ago
    I imagine this would add a lot overhead when the git admins are not well-versed in all subprojects of the monorepo.
- jerf 7y ago
  "Really, the one consistent thing is that if you have a good team, you'll make it work no matter what tech or decisions you make (assuming you're also good enough to know when you've lost and change course), and if you're a bad team, you're doomed to failure, because, well, you're bad (by definition)." The middle ground is vast, and nuanced in many dimensions. Which is a good thing, because there sure aren't very many large, good teams (by this definition of "good").
  - cbanek 7y ago
    Totally agree. Also many teams aren't all "good" or "bad" people, but more a mix of people with different skillsets and viewpoints, and it's not as if all good people think you should do it one way, and bad people the other. I think the normal case though is that there are too many cooks, and they spoil the broth. I've had teams where one person wants to go off and make their own repo just because, and can't be convinced to follow the rest of the team. Sometimes these are good people, although I find a lot of "bad" people don't want to be team players and be consistent, even if being consistent means doing something they don't like.
wellpast 7y ago
> Monorepo is great if you're really good, but absolutely terrible if you're not that good. > Multiple repos, on the other hand, are passable for everyone – they're never great, but they're never truly terrible, either. The calculus is trickier than this. He thinks the above is true because of this other thing he says: > With multiple repos, modularity is the norm. But if this were true, being "Good" would be easy. I wish programming tools were this able. Then I could go to the pool every day! But just because you're using some feature of a build or programming system -- like modules or classes or namespaces -- doesn't mean you get the win. Certainly doesn't mean you know how to wield these tools. In the end the technical feature doesn't save you. You actually have to have a hard-earned skill, which is how to properly modularize code into stable components with narrow stable interfaces and all of that. This skill is very rare ime. Now back to monorepo vs modules. If you use modules but you suck at modularization you're going to be paying a huge tax. Because you'll be creating volatile code/interfaces and you'll have to go through a process each change. You will be amplifying the tax from your lack of skill that you wouldn't if you were just in a single monorepo. On the other hand if you use a monorepo and you suck, you won't experience ^^this^^ pain and you'll be at a much higher probability of staying sucking. In short, programming language and build features don't bestow skills.
tudelo 7y ago
Coming from a small company with a monorepo to a large team with a monorepo, it seems to work fine. But maybe I need to be exposed more to other workflows.
yongjik 7y ago
> With multiple repos, modularity is the norm. (...) With a monorepo, modularity is a mere ideal. > ... > In a not-so-good team, your monorepo will grow into a single giant ball of circular dependencies. Sounds like the author was lucky enough to not encounter a not-so-good team with multiple repos.... :D
willeh 7y ago
I don't agree with the author that the quality of the team is what determines if a mono-repo is appropriate or not. It doesn't really matter if you use a mono-repo or not, what matters is what individual engineers are empowered to do. If engineers or even team-leads don't have permission to create a repo themselves well then you're probably going to see benefits from a monorepo. At the same time if you have say a ~100 people sharing a repo then you have to make sure that you have tooling that allows each team to customize their building and test environments themselves, which is hard because many CI solutions assume that One Repo = One Build status. Implicit in the author's reasoning is the principle that good engineers don't make mistakes; they don't break the build, not ever. But of course they do, everyone does, and if you have a hundred developers builds will be broken and people's productivity ruined. Perhaps because we're an industry so prone to failure we keep looking for that one solution, that given a good team makes all problems go away. Agile, XP, Monorepos, Containers, Microservices: we tell ourselves will solve our problems and get those pesky business people off our backs for good. But they won't and never will. What really matters is enablement, how can we get our code into production doing what it was intended to do without having your toes stepped on all the time. If you design your processes and tooling around enablement not the cargo-cult flavour of the month buzzword invented in the modern beautifully architected, yet completely open office spaces of one of the FAANG companies, then maybe then you can get some actual results.
- marcosdumay 7y ago
  > Implicit in the author's reasoning is the principle that good engineers don't make mistakes; they don't break the build, not ever. They don't, ever, because the VCS refuses a push if it breaks the build. That's the problem with all those single-repo discussions. It works perfectly well if you have all the tooling that makes a single repo work like a multi-repo. And it's great because you can enforce behind the scenes that everything is coherent... Except that you can enforce the same thing on a multi-repo if you write the equivalent tooling. All the points are completely moot, except the one that if you don't have a ton of tooling, a single-repo won't work at all, while a multi-repo will just be not great.
  - YawningAngel 7y ago
JamesBarney 7y ago
Ugh I don't like his use of the word dumbass. Coding is hard, it's easy to break things. We've developed lots of tools of strategies so we don't have to rely on people getting it right every time. Branching: getting forked by your worst programmer This example seems contrived I've never worked anywhere where having a fork that works for some scenarios and not others is tolerated for long. This would be given the highest priority. Modularity: demoted from a norm to an ideal This is basically saying a multi-repo makes it hard to reuse your own code which increases modularity. I find devs on very large projects are already reticent to reuse code from other projects/teams, but this pushes them even farther to rewrite domain logic that should probably be shared. In most cases I'd trade a little bit of modularity for increased domain logic consistency. Tooling: is yours better than the standard? There are few organizations that have so much code they break available source control solutions but simultaneously don't have the technical expertise to manage a monorepo that large. For these I guess it makes sense to break it up into manageable peaces based on the relationships between your projects. I've worked on subpar teams that decided against monorepo and it was a nightmare. It took forever to get setup, the build time was days, and cross repo edits were painful. They regretted going multi-repo.
- hashkb 7y ago
  > We've developed lots of tools of strategies so we don't have to rely on people getting it right every time. I think one of the points of the article is that this isn't (sufficiently) true; people will use tools incorrectly and make excuses for deviating from the strategy often enough that it's a problem. > Ugh I don't like his use of the word dumbass Substitute "well-meaning person who makes a totally understandable process mistake"
  - deleted 7y ago
    [deleted]
- bartread 7y ago
  > cross repo edits were painful. We are moving to a mono-repo for this very reason. Debugging something where you had to make changes to multiple projects, wait for those changes to go through the build pipeline, pull in updated packages in projects that depended on them, then change those projects (and on), was a complete nightmare. We're a bit over halfway there (the most painful half) and I expect us to get the rest done sometime in the next 3 months or so. Not looking back. At all.
jsw 7y ago
I’m firmly on team monorepo, and I agree great tooling is an absolute requirement. We use Bazel + AWS CodeBuild with local caching. We have an average incremental CI build of our monorepo that’s under 45 seconds. Clean build 30+ minutes.
drudru11 7y ago
So glad Yosef keeps writing on his blog. This is a well articulated gem. I had intuition as to why the monorepo style was not great for most shops. His clever argument nails it.
RHSeeger 7y ago
> What do you do when you have a branch working on Android and another branch working on iOS and you have deliveries on both platforms? You postpone the merge, and keep the fork. Honestly, it never occurred to me that you're deploy from more than one branch. If you can't merge the branches into <your main branch that releases are built from>, then what's in the branch doesn't make it into a release (from my experience).
- larrik 7y ago
  Seriously, this part threw me hard. Having multiple active forks is not something that's ever been considered as an option anywhere I've worked. Worse, I'm not convinced multi-repo even fixes this issue if you already have a culture that allows multiple active forks. For instance, big app rewrite, half-new REST API on the backend. Oh, but we need to maintain the old app APIs for those who can't update (like SuperImportantCustomer). Better fork!
  - rurounijones 7y ago
    I suppose it depends on your definition of "active" here but having release branches for previous major versions that are still supported with things like backported security fixes etc. is a pretty common setup.
- 0xEFF 7y ago
  > Honestly, it never occurred to me that you're deploy from more than one branch. Release branches! Deploy 1.1 from the 1.x branch on the same day you deploy 2.2 from the 2.x branch. 1.x merges into 2.x which merged into master.
draw_down 7y ago
Why is this person spending so much time alluding to Google being evil (without having the guts to come out and say it) in a post about git repositories?
sandGorgon 7y ago
>>>* They don't like to have to clone lots of other repos, and to then worry about their versions (in part because the tooling support for this might be less than great).* I think this is the argument around which the whole post is made. Everyone does want to work in a small space where they control everything. I want to see git log with just my code commits - so I'll make a microservice out of it. All other arguments are just there to wrap this one. I think it's wrong. At an organisational level, a monorepo is more good than bad because it simplifies dependency management and makes for a low-ego team.
- humanrebar 7y ago
  Counterpoint: monorepos make it easier to neglect packaging and dependency management since it's mechanically possible to assume any files in source control are on-hand. This makes it trivial to have implicit dependencies and see the uglier implications of Hyrum's Law.
- andrewprock 7y ago
  It's not that hard to make a library/module, and then type: git log .
cjfd 7y ago
I think one should not underestimate the powers of the not-so-good-team to make anything go sour. Who says the not-so-good-team isn't going to make sure that any change needs to touch at least 3 repos and quite regularly as many as 10? As for the philosophical issue that yosefk raises, I generally advocate solutions that work for the case that the team is good. I tend to think that if the team is not good you would be cooked anyway. Also, if you raise the stakes people might actually start learning a bit.
ar_lan 7y ago
I find this article more compelling than Yossi's article: http://blog.shippable.com/our-journey-to-microservices-and-a-mono-repository http://blog.shippable.com/our-journey-to-microservices-and-a... Yossi's comes off extremely pretentious, without really explaining why people consider multi-repo projects to begin with.
cj 7y ago
> If you agree with the above, the choice is up to your personal philosophy. To me, for instance, it's a no-brainer The most obvious issue with this post is it fails to acknowledge that for any production scale company, you can't blindly say that a decision like this is a choice of personal philosophy (unless you're starting a brand new project from scratch, in which case, spending tons of time structuring repos well probably isn't your first priority since new projects have very little code). I'd love to see more articles that discuss repo structure in the context of a pre-existing codebase with hundreds of thousands of lines of production code and 10+ engineers collaborating on it. For anyone reading: I'd be interested to hear anecdotes from people working at companies that have successfully (or unsuccessfully) re-structured a monorepo, the reasons you did it, how much time was invested in the restructure, and whether you think it was a net positive long-term.
theamk 7y ago
That is very, very subjective > With multiple repos, modularity is the norm. It's not a must - you technically can have a repo depending on umpteen other repos. But your teammates expect to be able to work with their repo with a minimal set of dependencies. You'd think so.. but no. I am working with multi-repo project where some repos have about dozens of dependencies, all developed locally, and interdependent on each other. Bumping the basic repo is very hard and frustrating. I miss my monorepo every day, where I could just make a PR and fix all consumers at once, where I had a CI which would test all modules at once.
TheGRS 7y ago
There's some nuggets of good things to look out for in here, but "don't do monorepo because your team is full of dumbasses" feels like a useless argument, maybe even a little adversarial. Monorepos solve versioning problems very effectively, which would be a pro if you're worried about working with dumbasses.
DanFeldman 7y ago
My team just switched to a monorepo. It's been only a few weeks, so I can't claim any results yet, but we've lived w/ the pain of poly-repo for long enough that we were ready to invest in a single repo. We've spent a lot of time building and iterating a unified ci/cd environment to support the new repo. Previously each project had it's own test/deploy/build/publish story and usually it's own jenkins project. Now, each project is registered and triggers its own steps. Cross-project edits can happen in a single pull request. We have an incredible amount of integration tests (more so than unit tests), and getting them to work corss-project while migrating has been challenging. We've gone from ~10-15 actively maintained repos to about 3 as we're slowly migrating. We have a mix of services, libraries, and batch processing all mixed in. The authors points about forking and long-lived branching being incredibly difficult for most teams is really crucial. We're going to have to invest in education for new members about WHY we have a monorepo, what it means for your development, and how to change your perspective for developing at HEAD. I don't think 'bad' developers make it easier or harder. Instead, clearly articulating behaviors that exist in a poly-repo vs mono-repo world to developers is the Differentiator. These articles were absolutely crucial to developing our monorepo. https://trunkbaseddevelopment.com/ https://trunkbaseddevelopment.com/ http://blog.shippable.com/ci/cd-of-microservices-using-mono-repos http://blog.shippable.com/ci/cd-of-microservices-using-mono-... https://www.godaddy.com/engineering/2018/06/05/cicd-best-practices/ https://www.godaddy.com/engineering/2018/06/05/cicd-best-pra...
- humanrebar 7y ago
  I suspect for that number of projects monorepos make a lot of sense. The major technology organizations we hear about usually have at least several monorepos, due to the legacies of acquisitions and mergers if nothing else. At the scale of thousands of subprojects, I am not entirely sure the benefits are as advertised. There will be support of subprojects forked to public github.com or gitlab.com if nothing else. And there will be external dependencies to manage; system level libraries like openssl and libc if nothing else. Even if they are vendored in to the monorepo, any upstream regression is a significant problem in a monorepo... and the problem sometimes has to be solved in a big bang instead of incrementally.
  - 7y ago
jasim 7y ago
Linus Torvalds said something about this, in relation to microkernels. But the gist is in how interactions between many pieces makes the whole thing complex. Here's the quote from his book "Just for Fun". "The theory behind the microkernel is that operating systems are complicated. So you try to get some of the complexity out by modularizing it a lot. The tenet of the microkernel approach is that the kernel, which is the core of the core of the core, should do as little as possible. Its main function is to communicate. All the different things that the computer offers are services that are available through the microkernel communications channels. In the microkernel approach, you’re supposed to split up the problem space so much that none of it is complex. I thought this was stupid. Yes, it makes every single piece simple. But the interactions make it far more complex than it would be if many of the services were included in the kernel itself, as they are in Linux. Think of your brain. Every single piece is simple, but the interactions between the pieces make for a highly complex system. It’s the whole-is-bigger-than-the-parts problem. If you take a problem and split it in half and say that the halves are half as complicated, you’re ignoring the fact that you have to add in the complication of communication between the two halves. The theory behind the microkernel was that you split the kernel into fifty independent parts, and each of the parts is a fiftieth of the complexity. But then everybody ignores the fact that the communication among the parts is actually more complicated than the original system was—never mind the fact that the parts are still not trivial. That’s the biggest argument against microkernels. The simplicity you try to reach is a false simplicity."
- bartread 7y ago
  > "...The simplicity you try to reach is a false simplicity." Also applies to some microservice architectures I've seen. People completely disregard the complexity (and overhead!) of the interactions between microservices.
  - asdfman123 7y ago
    I feel like I've become a crusader against microservices for the same reason. They're so easy to set up and they immediately solve problems. But they also create many more, which aren't immediately obvious. And very few people are willing to say, "I was totally wrong to move to them, and let's spend some more precious time rolling them back."
burtonator 7y ago
One thing that's nice about a monorepo is if the language has modules. It it supports modules well you can isolate your code better but still keep it in one large repo. I dislike having all my code under one 'src' directory and it's nice to have modules like foo-ui and foo-util and so forth. Knowing that one module doesn't use ui components is nice because you can use it on the backend for example. But it's all fully integrated and tested together.
qznc 7y ago
Does anybody know some monorepo horror stories? I have heard plenty of people complain about their many-repo structure and wishing for a monorepo. I would like to hear some concrete story where a monorepo went wrong. This article is just abstract opinion.
- aidenn0 7y ago
  I asked a similar question a previous time the mono- vs many- repo question came out, and the few responses I got were roughly "The repo became many tens of gigabytes which was unwieldy"
  - andrewprock 7y ago
    Unfortunately, breaking a 10 gig repo into 5 repos often means you have to now download five 2 gig repos.
    - detaro 7y ago
      That can still be better, e.g. when part of the problem are tools that work on a per-repo level and fall over/get slow if the repo gets to large.
      - andrewprock 7y ago
        How do these tools work when it comes to working on multiple repos? I imagine they either don't, or that it's worse than working on a single monorepo of the same size.
- mr_tristan 7y ago
  Oh yes. #1 problem I've experienced at multiple places: delaying integration with tons of branching. Usually the PM or PO force everyones to using some vague "product version" they track for public releases. Places that use monorepos well tend to have very few branches (like, maybe 2 or 3), which have nothing to do with your public product versioning scheme, and instead use "branch by abstraction" to stay integrated. But what I end up seeing, is that the product team and middle management gets involved with dictating version control, e.g., "this will be version 1.2, and then that should be 2.3, ok let's cut those branches...", and then they change their minds as some team has to delay and before another is ready. And then bugs start rolling in from both testing and they don't know what to do, and they start asking people to just "get it done", and then, things really start falling apart. You add 10+ teams trying to use branches for their own work based off of god knows what and it becomes a mess of crazy integration problems. I seriously think that a huge benefit of multiple repositories, is that is scares the pseudo-technical managers and product people into not bothering with trying to track or dictate usage of the version control system.
justinmchase 7y ago
Its funny and makes some good points but I don't think the distinction is between good and bad teams but whether or not you're 1 team or more. If one team has one application that is split across multiple repositories it can be a productivity boost and a simplification to unite them into a single repo with some single tools and norms. If you have two teams working primarily on two sets of repos and two different systems or applications, by all means split them into two (or more) repos. Just be cause its called a "monorepo" doesn't mean you can't have more than one! It may be simpler to have one, it may be simpler to have many. Do whats simpler for you! I happen to think that it primarily depends on how your teams are organized more than on who is in the teams or their "badness" levels.
- AmericanChopper 7y ago
  I think this only works if the teams are actually working on different products. If Team A and Team B are both writing to and reading from the same data stores, then I’d say they’re likely both working on the same product, and you have a multirepo.
aboodman 7y ago
One interesting new thing in this post that I've not seen in this debate is that polyrepos tend to enforce acyclical dependency graphs. All monorepo projects I've ever worked on enforced the same either through the language involved or mechanically, and it was universally a good thing.
kazinator 7y ago
Let's assume without proof that Glibc developers are good. Similarly, kernel.org developers are good as are the gcc.gnu.org people. Should glibc, gcc and the kernel be in a monorepo? (Cue laugh track ...)
- dboreham 7y ago
  Did you just invent the unikernel?
  - teddyh 7y ago
    AFAIK, Unix did this, so BSD Unix did this, and the modern BSD derivatives still do this.
- NikkiA 7y ago
  This is the red tinged future linux is headed towards anyway.
- sally1620 7y ago
  That is actually one of the advantages of the BSDs. Kernel and base system are in one repo and released together. It simplifies development and testing. and an easier upgrade for end-users.
scarejunba 7y ago
You're just pushing your trouble into a shadow layer that's hidden. You still have just as much complexity. It's just not encoded. If branch A on repo X will only work with branch B on repo Y, you're holding that relationship in an uncoded way. It's true and unrepresented, and you never want that.
reilly3000 7y ago
I think the whole idea of simplicity vs complexity, and the linked article "Worse is Better" is fundamentally ill-conceived. Simple vs. Complex is contextually relative. Literally every observer is subject to their own opinion of a design. Success in the wild = success. I think success in the wild, especially in our age of information overload, depends on being "convenient to understand and operate". A 'simple' solution may not be easy to grok. Few people think at the level of axioms. A survivable solution must be passed along to many people across generations. For some, monorepos are simple because that is what they know, for others multirepos are the norm. The survival of the firms that adopt these strategies will somewhat dictate what repo strategy propagates in the world, not the best design.
dboreham 7y ago
Always makes me think of a philips radio my Dad told me about called the "Mono Knob". It had a complex design that allowed control via just one knob. He said they were always in the shop for repair when he worked as a teenager in a radio store. https://www.thevalvepage.com/radios/philips/785ax/785ax.htm https://www.thevalvepage.com/radios/philips/785ax/785ax.htm
mark_l_watson 7y ago
My primary language now is Common Lisp and I have one mother of all mono repos for all of my personal Common Lisp code. I set the root of this repo as a Quicklisp load point so all my libraries and applications are available with a Quicklisp load. Life is good. I don’t quite get the point of this article though. I am a very enthusiastic but not rockstar programmer, and I don’t have problems with a large mono repo.
- drewm1980 7y ago
  He is talking about big teams.
- gumby 7y ago
  But you're one person. The article argues that a single repo is unmanageable when you have many devs working at the same time.
jnurmine 7y ago
Is the monorepo/multirepo choice really the most important thing to consider? Branching: monorepo or not, if a feature-incomplete development branch for one of the supported targets can "hold the entire organization as a hostage" then the SCM people, and/or persons responsible of the SCM policy, should do some introspection... Why are deliveries done from a branch which is obviously still in development? Why does code-to-be-released need to depend on incomplete work? Why aren't something like "topic branches" used? Modularity: monorepo or not, problems will certainly appear when the complexity of implementation outpaces the capacity created by the design. To get modularity, one needs actual modules with properly designed (=not brittle, DRY, KISS, YAGNI, SOLID, etc. etc.) interfaces between the modules. Now, does monorepo/multirepo really play a role here at all? If everyday changes are constantly modifying the module interfaces in incompatible ways which breaks existing code, this speaks something about the design, or rather the insufficiency of it. Of course, every project and team is different. However, even if a locally optimal choice for the monorepo vs. multirepo question is found, problems existing regardless of monorepo/multirepo will still be there.
- jknoepfler 7y ago
  I was wondering the same thing. Like, I use a microservice architecture at work, but the choice of using one vs. many git repos to represent diffs in those services over time seems largely meaningless. I don't like large diffs or people breaking production, but this is solved by testing and insisting upon small diffs, not by how many git repos we use. Formally speaking, multi-repo management allows a strict subset of the diffs allowed to a mono-repo (because diffs can 't extend beyond each repo root). Are the excluded possibilities all bad? No. Are they generally bad? Not really. Are they sometimes bad? Sure. Are they sometimes better than many diffs across many repos? Sure. Can a reasonably competent dev team tell the difference? Sure, usually. Unsurprisingly, this usually requires the exact same tooling as ensuring the quality of microrepo changes. If you're continuously deploying master, have a healthy ci/cd pipeline, and enforce good merging discipline, you're fine either way. I'm a little tired of doing things like revving our trace and logging libraries across our 50+ micro repos that represent microservices. That's genuinely obnoxious. Is it bad? No. Is it obviously more or less error prone than the equivalent monorepo update? No. All the bad bits of either strategy just require some tooling and a clear head.
jayd16 7y ago
>bad fork How is this an argument? You merge the unforked projects and its the equivalent to multirepo. I don't follow the argument at all. ...I started writing rebuttals to the others but I guess when your argument is "yeah you can do it right but you _could_ do it wrong and I have defined the question in such a way that we err on success for multi-repo and err on failure on mono-repo" I can't really fight that.
ThePhysicist 7y ago
Does anyone here have experience using submodules to tie individual repositories together? We've been using this in our small startup (only a few developers) and so far it works nicely. It allows us to check out and develop repositories individually but at the same time maintain an exact dependency graph for our entire system. You can for example have a single repository that ties together different projects and has submodules that contain specific references e.g. to the frontend, backend and deployment repositories. You can then use this master repository e.g. for deployment and integration testing. Gitlab makes CI/CD in such a setup very easy and checks out submodules recursively during a build, even across groups. The drawback is that not many people are familiar with submodules and they can be a bit tedious to set up, though working with a submodule is almost like working with a normal file in git. One danger is of course that branching between individual submodules can get messy. Another nuisance might be that you have to commit recursively, i.e. if you have one repository with a submodule to which you make changes you need to first commit these changes in the submodule and then create a new commit in the parent repository that adds the new version of the submodule. Maybe this is a good thing though as it forces you to commit changes individually in each submodule before committing a larger change into your main repository. In general I would avoid nesting submodules more than two levels deep, as this can quickly get confusing. In the past I've also worked on a large mono-repositoriy and enjoyed it as well, just curious to hear if anybody has used submodules in a larger team.
- zaphod12 7y ago
  Yes, I have experience and it has always seemed a great idea with a handful of developers and then come back to be a disaster when the team scaled. They become a nightmare to keep everything properly up to date when you have a lot of people working on all of it. Git sub repos worked a bit better, but overall I really recommend submodules exclusively when the submoduled repo changes very infrequently.
- the_gipsy 7y ago
  I have bad experiences with submodules. It was only one submodule just one level deep, and it only contained something like a convoluted configuration shared among multiple repos. As you say, getting a change first into the child and then into the parent requires double PRs and testing. But that's the same as if you had it as a package dependency. Only that instead of a version, you have a sha1 which you never know what it is. I prefer package dependency, because it forces you to explicitly make a release, where it should have passed PR and some integration tests. Also merge conflicts are clearer.
jupp0r 7y ago
There is also a way to simultaneously reap the drawbacks of monorepos and multirepos: consolidate numerous small repos into somewhat big monorepos and then don't merge everything into one big repo. This way, you'll have to deal with * difficult tooling * dependency hell between the mono repos (which are now way more tightly coupled due to the dependency graph between them being denser) * long living branches causing way more collateral damage as described in the original article * cross-repo changes have become even harder for all the reasons above You get all the bad things and avoid those advantages! Welcome to my world :)
galkk 7y ago
I've experienced 3 large codebases with different approaches: 1. Monorepo: Google3 2. Non monorepo, large pile of #@$: Microsoft Exchange 3. Non monorepo, Amazon After working with them, from my personal experience, monorepo was the best. Yes, Google has ton of internal stuff and they could go away with not using much of external dependencies, but when everything works, it works like a charm. Convenience of defining protobufs/contracts, ease of reference them and ton of the things are given to you when you're in the system. At Google I never felt that the system is hostile to you. It was extremely easy to start hacking something if you'd like to. Yes, it's not only monorepo, but the overall quality of the tools available, but monorepo is also quite a significant part of it.
rosstafarian0 7y ago
Is being demeaning and rigid just the cool thing to do today in blogs. I feel like I keep reading articles like this every day now. "Well if your team is full of dumbasses" or "If you use OO instead of functional programming"
- NikkiA 7y ago
  Have you not noticed that this is the new norm everywhere?
lootsauce 7y ago
I feel like I’m missing something. Never used monorepo before but looking into it for our node code base. It seems like the combination of a monorepo and individually publishing the packages to a private npm server such as nexus eliminates many of these issues. One project can remain using an older version while another can use a breaking change. Pin your versions and follow semver and you should be fine. What am I missing here?
sally1620 7y ago
What author misses is that multi-repo is also not dumbass proof. Our team of about 60 people owned about 5-6 git repos that compiled into one SO. Every simple bug fix required multiple diffs to multiple repos. The real argument that the author is making is that worse is better. Monorepo requires good tooling and a disciplined team. Multi-repo is worse but it is easier to manage when dealing with inexperienced programmers who want to have their own repo for their shiny little microservice. IMO, the difference is that multi-repo has limitations and mono-repo has challenges. You will never get atomic commits and precise versioning in multi-repo. With mono-repo, there are a lot of challenges that can be solved with good engineering.
epage 7y ago
This reminds me of some the trade-offs I've looked at with monorepos: https://epage.github.io/dev/monorepos/ https://epage.github.io/dev/monorepos/
hinkley 7y ago
One of the tenets of XP that survived (or should I say, is amplified?) into CI/CD is the idea that you should build up callouses for painful activities instead of trying to avoid them. In that context, if a thing is tough but has value, you make a path to it. First make the tools consistent, and then make people consistently use the tools. The more predictable the system becomes (predictability is the opposite of magic!), the more you insist on people using it. Pushback is a kind of feedback, and you have to address at least some of the concerns of people who refuse ('meet me halfway here'). Someday it will shock no-one to say that Git is not the best of all possible version control tools. If this is difficult, it may not be the people. Maybe it's time to start thinking about the next version control system? SVN had some pretty decent facilities for monorepos. Some people will tell you that Git traded some of these features for others, but looking through the information architecture documentation for git, I don't think I can agree. Some of that information is there, it's just maybe not packaged for consumption.
hinkley 7y ago
> In a Good team, you don't have multiple concurrent branches from which actual product deliveries are produced, and/or where most people get to maintain these branches simultaneously for a long time. These sorts of Black and White, naked assertions drive me nuts. Buried in this statement is an assumption that the only software model worth even discussing is SaaS software - all copies of the code being run are run by your team, so master@HEAD is our ground truth at all times (except during deployments, which BTW are happening at least 10 minutes out of every hour of every day...) Teams that sell applications or allow self-hosting, or even some SaaS shops with large enough customers are going to have to maintain multiple release branches. Possibly for years. From personal experience, anything above 3 seems to become unsustainable. But having 3 repos (a monorepo with 2 active branches + master) may be the right answer for you. One can't work, and 100 is murder. Stop the pendulum in the middle.

> like Google, the ultimate force for Good in technology Hahaha... https://www.reddit.com/r/degoogle/ https://www.reddit.com/r/degoogle/ https://twitter.com/hashtag/degoogle https://twitter.com/hashtag/degoogle

dmitriz 7y ago

> What do you do when you have a branch working on Android and another branch working on iOS and you have deliveries on both platforms? Stop it and focus on one single web app instead that anyone can run. Unless your app is going to be in the top 10 that people can't miss downloading.

rezmason 7y ago

Ask your doctor if Monorepo is right for you.

ghostbrainalpha 7y ago
Individual results may vary. Don't take Monorepo if you are bad at programming, or if you may become bad at programming. Side effects include but are not limited to your repo growing into a single giant ball of circular dependencies.
- newshorts 7y ago
  Monorepo may cause blindness, sleep deprivation and suicidal thoughts. If you experience any of these symptoms, stop taking monorepo and consult your manager.
  - asark 7y ago
    If you experience a build lasting more than six hours, seek rockstar ninja help immediately.
vidanay 7y ago
Ask not what your monorepo can do for you - ask what you can do for your monorepo.
asdfman123 7y ago
In the real world, it doesn't work that way. In the real world you ask your doctor if it's okay and he says "sure" because he's read a few things about it and it's what you seem to want. But he doesn't really know, because no one is capable of understanding the human body in its full complexity. So you just end up taking Monorepo and hoping it doesn't make you severely depressed or give you seizures that send you to the emergency room.

cbanek 7y ago

> the entire code base got forked, and the entire org is now held hostage by the dumbass. > Of course in a Good team, needless dependencies would be weeded out in code reviews, and a Culture would evolve over time avoiding needless dependencies. Really, the one consistent thing is that if you have a good team, you'll make it work no matter what tech or decisions you make (assuming you're also good enough to know when you've lost and change course), and if you're a bad team, you're doomed to failure, because, well, you're bad (by definition). I think this article also vastly underestimates the cost and annoyance of the tooling of CI'ing a large number of repos, especially if you have to match or do some kind of cross product on the feature branches. (such as, repo A branch B can only be built with repo C branch F, but all the other repos should be master)

humbleMouse 7y ago
Umm, appoint someone or a trusted few as git admins and only allow them to merge commits? (responding to the article contents quoted in above comment)
- grenoire 7y ago
  I imagine this would add a lot overhead when the git admins are not well-versed in all subprojects of the monorepo.
jerf 7y ago
"Really, the one consistent thing is that if you have a good team, you'll make it work no matter what tech or decisions you make (assuming you're also good enough to know when you've lost and change course), and if you're a bad team, you're doomed to failure, because, well, you're bad (by definition)." The middle ground is vast, and nuanced in many dimensions. Which is a good thing, because there sure aren't very many large, good teams (by this definition of "good").
- cbanek 7y ago
  Totally agree. Also many teams aren't all "good" or "bad" people, but more a mix of people with different skillsets and viewpoints, and it's not as if all good people think you should do it one way, and bad people the other. I think the normal case though is that there are too many cooks, and they spoil the broth. I've had teams where one person wants to go off and make their own repo just because, and can't be convinced to follow the rest of the team. Sometimes these are good people, although I find a lot of "bad" people don't want to be team players and be consistent, even if being consistent means doing something they don't like.

wellpast 7y ago

> Monorepo is great if you're really good, but absolutely terrible if you're not that good. > Multiple repos, on the other hand, are passable for everyone – they're never great, but they're never truly terrible, either. The calculus is trickier than this. He thinks the above is true because of this other thing he says: > With multiple repos, modularity is the norm. But if this were true, being "Good" would be easy. I wish programming tools were this able. Then I could go to the pool every day! But just because you're using some feature of a build or programming system -- like modules or classes or namespaces -- doesn't mean you get the win. Certainly doesn't mean you know how to wield these tools. In the end the technical feature doesn't save you. You actually have to have a hard-earned skill, which is how to properly modularize code into stable components with narrow stable interfaces and all of that. This skill is very rare ime. Now back to monorepo vs modules. If you use modules but you suck at modularization you're going to be paying a huge tax. Because you'll be creating volatile code/interfaces and you'll have to go through a process each change. You will be amplifying the tax from your lack of skill that you wouldn't if you were just in a single monorepo. On the other hand if you use a monorepo and you suck, you won't experience ^^this^^ pain and you'll be at a much higher probability of staying sucking. In short, programming language and build features don't bestow skills.

tudelo 7y ago

Coming from a small company with a monorepo to a large team with a monorepo, it seems to work fine. But maybe I need to be exposed more to other workflows.

yongjik 7y ago

> With multiple repos, modularity is the norm. (...) With a monorepo, modularity is a mere ideal. > ... > In a not-so-good team, your monorepo will grow into a single giant ball of circular dependencies. Sounds like the author was lucky enough to not encounter a not-so-good team with multiple repos.... :D

willeh 7y ago

I don't agree with the author that the quality of the team is what determines if a mono-repo is appropriate or not. It doesn't really matter if you use a mono-repo or not, what matters is what individual engineers are empowered to do. If engineers or even team-leads don't have permission to create a repo themselves well then you're probably going to see benefits from a monorepo. At the same time if you have say a ~100 people sharing a repo then you have to make sure that you have tooling that allows each team to customize their building and test environments themselves, which is hard because many CI solutions assume that One Repo = One Build status. Implicit in the author's reasoning is the principle that good engineers don't make mistakes; they don't break the build, not ever. But of course they do, everyone does, and if you have a hundred developers builds will be broken and people's productivity ruined. Perhaps because we're an industry so prone to failure we keep looking for that one solution, that given a good team makes all problems go away. Agile, XP, Monorepos, Containers, Microservices: we tell ourselves will solve our problems and get those pesky business people off our backs for good. But they won't and never will. What really matters is enablement, how can we get our code into production doing what it was intended to do without having your toes stepped on all the time. If you design your processes and tooling around enablement not the cargo-cult flavour of the month buzzword invented in the modern beautifully architected, yet completely open office spaces of one of the FAANG companies, then maybe then you can get some actual results.

marcosdumay 7y ago
> Implicit in the author's reasoning is the principle that good engineers don't make mistakes; they don't break the build, not ever. They don't, ever, because the VCS refuses a push if it breaks the build. That's the problem with all those single-repo discussions. It works perfectly well if you have all the tooling that makes a single repo work like a multi-repo. And it's great because you can enforce behind the scenes that everything is coherent... Except that you can enforce the same thing on a multi-repo if you write the equivalent tooling. All the points are completely moot, except the one that if you don't have a ton of tooling, a single-repo won't work at all, while a multi-repo will just be not great.
- YawningAngel 7y ago

JamesBarney 7y ago

Ugh I don't like his use of the word dumbass. Coding is hard, it's easy to break things. We've developed lots of tools of strategies so we don't have to rely on people getting it right every time. Branching: getting forked by your worst programmer This example seems contrived I've never worked anywhere where having a fork that works for some scenarios and not others is tolerated for long. This would be given the highest priority. Modularity: demoted from a norm to an ideal This is basically saying a multi-repo makes it hard to reuse your own code which increases modularity. I find devs on very large projects are already reticent to reuse code from other projects/teams, but this pushes them even farther to rewrite domain logic that should probably be shared. In most cases I'd trade a little bit of modularity for increased domain logic consistency. Tooling: is yours better than the standard? There are few organizations that have so much code they break available source control solutions but simultaneously don't have the technical expertise to manage a monorepo that large. For these I guess it makes sense to break it up into manageable peaces based on the relationships between your projects. I've worked on subpar teams that decided against monorepo and it was a nightmare. It took forever to get setup, the build time was days, and cross repo edits were painful. They regretted going multi-repo.

hashkb 7y ago
> We've developed lots of tools of strategies so we don't have to rely on people getting it right every time. I think one of the points of the article is that this isn't (sufficiently) true; people will use tools incorrectly and make excuses for deviating from the strategy often enough that it's a problem. > Ugh I don't like his use of the word dumbass Substitute "well-meaning person who makes a totally understandable process mistake"
- deleted 7y ago
  [deleted]
bartread 7y ago
> cross repo edits were painful. We are moving to a mono-repo for this very reason. Debugging something where you had to make changes to multiple projects, wait for those changes to go through the build pipeline, pull in updated packages in projects that depended on them, then change those projects (and on), was a complete nightmare. We're a bit over halfway there (the most painful half) and I expect us to get the rest done sometime in the next 3 months or so. Not looking back. At all.

jsw 7y ago

I’m firmly on team monorepo, and I agree great tooling is an absolute requirement. We use Bazel + AWS CodeBuild with local caching. We have an average incremental CI build of our monorepo that’s under 45 seconds. Clean build 30+ minutes.

drudru11 7y ago

So glad Yosef keeps writing on his blog. This is a well articulated gem. I had intuition as to why the monorepo style was not great for most shops. His clever argument nails it.

RHSeeger 7y ago

> What do you do when you have a branch working on Android and another branch working on iOS and you have deliveries on both platforms? You postpone the merge, and keep the fork. Honestly, it never occurred to me that you're deploy from more than one branch. If you can't merge the branches into <your main branch that releases are built from>, then what's in the branch doesn't make it into a release (from my experience).

larrik 7y ago
Seriously, this part threw me hard. Having multiple active forks is not something that's ever been considered as an option anywhere I've worked. Worse, I'm not convinced multi-repo even fixes this issue if you already have a culture that allows multiple active forks. For instance, big app rewrite, half-new REST API on the backend. Oh, but we need to maintain the old app APIs for those who can't update (like SuperImportantCustomer). Better fork!
- rurounijones 7y ago
  I suppose it depends on your definition of "active" here but having release branches for previous major versions that are still supported with things like backported security fixes etc. is a pretty common setup.
0xEFF 7y ago
> Honestly, it never occurred to me that you're deploy from more than one branch. Release branches! Deploy 1.1 from the 1.x branch on the same day you deploy 2.2 from the 2.x branch. 1.x merges into 2.x which merged into master.

draw_down 7y ago

Why is this person spending so much time alluding to Google being evil (without having the guts to come out and say it) in a post about git repositories?

sandGorgon 7y ago

>>>* They don't like to have to clone lots of other repos, and to then worry about their versions (in part because the tooling support for this might be less than great).* I think this is the argument around which the whole post is made. Everyone does want to work in a small space where they control everything. I want to see git log with just my code commits - so I'll make a microservice out of it. All other arguments are just there to wrap this one. I think it's wrong. At an organisational level, a monorepo is more good than bad because it simplifies dependency management and makes for a low-ego team.

humanrebar 7y ago
Counterpoint: monorepos make it easier to neglect packaging and dependency management since it's mechanically possible to assume any files in source control are on-hand. This makes it trivial to have implicit dependencies and see the uglier implications of Hyrum's Law.
andrewprock 7y ago
It's not that hard to make a library/module, and then type: git log .

cjfd 7y ago

I think one should not underestimate the powers of the not-so-good-team to make anything go sour. Who says the not-so-good-team isn't going to make sure that any change needs to touch at least 3 repos and quite regularly as many as 10? As for the philosophical issue that yosefk raises, I generally advocate solutions that work for the case that the team is good. I tend to think that if the team is not good you would be cooked anyway. Also, if you raise the stakes people might actually start learning a bit.

ar_lan 7y ago

I find this article more compelling than Yossi's article: http://blog.shippable.com/our-journey-to-microservices-and-a-mono-repository http://blog.shippable.com/our-journey-to-microservices-and-a... Yossi's comes off extremely pretentious, without really explaining why people consider multi-repo projects to begin with.

cj 7y ago

> If you agree with the above, the choice is up to your personal philosophy. To me, for instance, it's a no-brainer The most obvious issue with this post is it fails to acknowledge that for any production scale company, you can't blindly say that a decision like this is a choice of personal philosophy (unless you're starting a brand new project from scratch, in which case, spending tons of time structuring repos well probably isn't your first priority since new projects have very little code). I'd love to see more articles that discuss repo structure in the context of a pre-existing codebase with hundreds of thousands of lines of production code and 10+ engineers collaborating on it. For anyone reading: I'd be interested to hear anecdotes from people working at companies that have successfully (or unsuccessfully) re-structured a monorepo, the reasons you did it, how much time was invested in the restructure, and whether you think it was a net positive long-term.

theamk 7y ago

That is very, very subjective > With multiple repos, modularity is the norm. It's not a must - you technically can have a repo depending on umpteen other repos. But your teammates expect to be able to work with their repo with a minimal set of dependencies. You'd think so.. but no. I am working with multi-repo project where some repos have about dozens of dependencies, all developed locally, and interdependent on each other. Bumping the basic repo is very hard and frustrating. I miss my monorepo every day, where I could just make a PR and fix all consumers at once, where I had a CI which would test all modules at once.

TheGRS 7y ago

There's some nuggets of good things to look out for in here, but "don't do monorepo because your team is full of dumbasses" feels like a useless argument, maybe even a little adversarial. Monorepos solve versioning problems very effectively, which would be a pro if you're worried about working with dumbasses.

DanFeldman 7y ago

My team just switched to a monorepo. It's been only a few weeks, so I can't claim any results yet, but we've lived w/ the pain of poly-repo for long enough that we were ready to invest in a single repo. We've spent a lot of time building and iterating a unified ci/cd environment to support the new repo. Previously each project had it's own test/deploy/build/publish story and usually it's own jenkins project. Now, each project is registered and triggers its own steps. Cross-project edits can happen in a single pull request. We have an incredible amount of integration tests (more so than unit tests), and getting them to work corss-project while migrating has been challenging. We've gone from ~10-15 actively maintained repos to about 3 as we're slowly migrating. We have a mix of services, libraries, and batch processing all mixed in. The authors points about forking and long-lived branching being incredibly difficult for most teams is really crucial. We're going to have to invest in education for new members about WHY we have a monorepo, what it means for your development, and how to change your perspective for developing at HEAD. I don't think 'bad' developers make it easier or harder. Instead, clearly articulating behaviors that exist in a poly-repo vs mono-repo world to developers is the Differentiator. These articles were absolutely crucial to developing our monorepo. https://trunkbaseddevelopment.com/ https://trunkbaseddevelopment.com/ http://blog.shippable.com/ci/cd-of-microservices-using-mono-repos http://blog.shippable.com/ci/cd-of-microservices-using-mono-... https://www.godaddy.com/engineering/2018/06/05/cicd-best-practices/ https://www.godaddy.com/engineering/2018/06/05/cicd-best-pra...

humanrebar 7y ago
I suspect for that number of projects monorepos make a lot of sense. The major technology organizations we hear about usually have at least several monorepos, due to the legacies of acquisitions and mergers if nothing else. At the scale of thousands of subprojects, I am not entirely sure the benefits are as advertised. There will be support of subprojects forked to public github.com or gitlab.com if nothing else. And there will be external dependencies to manage; system level libraries like openssl and libc if nothing else. Even if they are vendored in to the monorepo, any upstream regression is a significant problem in a monorepo... and the problem sometimes has to be solved in a big bang instead of incrementally.
- 7y ago

jasim 7y ago

Linus Torvalds said something about this, in relation to microkernels. But the gist is in how interactions between many pieces makes the whole thing complex. Here's the quote from his book "Just for Fun". "The theory behind the microkernel is that operating systems are complicated. So you try to get some of the complexity out by modularizing it a lot. The tenet of the microkernel approach is that the kernel, which is the core of the core of the core, should do as little as possible. Its main function is to communicate. All the different things that the computer offers are services that are available through the microkernel communications channels. In the microkernel approach, you’re supposed to split up the problem space so much that none of it is complex. I thought this was stupid. Yes, it makes every single piece simple. But the interactions make it far more complex than it would be if many of the services were included in the kernel itself, as they are in Linux. Think of your brain. Every single piece is simple, but the interactions between the pieces make for a highly complex system. It’s the whole-is-bigger-than-the-parts problem. If you take a problem and split it in half and say that the halves are half as complicated, you’re ignoring the fact that you have to add in the complication of communication between the two halves. The theory behind the microkernel was that you split the kernel into fifty independent parts, and each of the parts is a fiftieth of the complexity. But then everybody ignores the fact that the communication among the parts is actually more complicated than the original system was—never mind the fact that the parts are still not trivial. That’s the biggest argument against microkernels. The simplicity you try to reach is a false simplicity."

bartread 7y ago
> "...The simplicity you try to reach is a false simplicity." Also applies to some microservice architectures I've seen. People completely disregard the complexity (and overhead!) of the interactions between microservices.
- asdfman123 7y ago
  I feel like I've become a crusader against microservices for the same reason. They're so easy to set up and they immediately solve problems. But they also create many more, which aren't immediately obvious. And very few people are willing to say, "I was totally wrong to move to them, and let's spend some more precious time rolling them back."

burtonator 7y ago

One thing that's nice about a monorepo is if the language has modules. It it supports modules well you can isolate your code better but still keep it in one large repo. I dislike having all my code under one 'src' directory and it's nice to have modules like foo-ui and foo-util and so forth. Knowing that one module doesn't use ui components is nice because you can use it on the backend for example. But it's all fully integrated and tested together.

qznc 7y ago

Does anybody know some monorepo horror stories? I have heard plenty of people complain about their many-repo structure and wishing for a monorepo. I would like to hear some concrete story where a monorepo went wrong. This article is just abstract opinion.

aidenn0 7y ago
I asked a similar question a previous time the mono- vs many- repo question came out, and the few responses I got were roughly "The repo became many tens of gigabytes which was unwieldy"
- andrewprock 7y ago
  Unfortunately, breaking a 10 gig repo into 5 repos often means you have to now download five 2 gig repos.
  - detaro 7y ago
    That can still be better, e.g. when part of the problem are tools that work on a per-repo level and fall over/get slow if the repo gets to large.
    - andrewprock 7y ago
      How do these tools work when it comes to working on multiple repos? I imagine they either don't, or that it's worse than working on a single monorepo of the same size.
mr_tristan 7y ago
Oh yes. #1 problem I've experienced at multiple places: delaying integration with tons of branching. Usually the PM or PO force everyones to using some vague "product version" they track for public releases. Places that use monorepos well tend to have very few branches (like, maybe 2 or 3), which have nothing to do with your public product versioning scheme, and instead use "branch by abstraction" to stay integrated. But what I end up seeing, is that the product team and middle management gets involved with dictating version control, e.g., "this will be version 1.2, and then that should be 2.3, ok let's cut those branches...", and then they change their minds as some team has to delay and before another is ready. And then bugs start rolling in from both testing and they don't know what to do, and they start asking people to just "get it done", and then, things really start falling apart. You add 10+ teams trying to use branches for their own work based off of god knows what and it becomes a mess of crazy integration problems. I seriously think that a huge benefit of multiple repositories, is that is scares the pseudo-technical managers and product people into not bothering with trying to track or dictate usage of the version control system.

justinmchase 7y ago

Its funny and makes some good points but I don't think the distinction is between good and bad teams but whether or not you're 1 team or more. If one team has one application that is split across multiple repositories it can be a productivity boost and a simplification to unite them into a single repo with some single tools and norms. If you have two teams working primarily on two sets of repos and two different systems or applications, by all means split them into two (or more) repos. Just be cause its called a "monorepo" doesn't mean you can't have more than one! It may be simpler to have one, it may be simpler to have many. Do whats simpler for you! I happen to think that it primarily depends on how your teams are organized more than on who is in the teams or their "badness" levels.

AmericanChopper 7y ago
I think this only works if the teams are actually working on different products. If Team A and Team B are both writing to and reading from the same data stores, then I’d say they’re likely both working on the same product, and you have a multirepo.

aboodman 7y ago

One interesting new thing in this post that I've not seen in this debate is that polyrepos tend to enforce acyclical dependency graphs. All monorepo projects I've ever worked on enforced the same either through the language involved or mechanically, and it was universally a good thing.

kazinator 7y ago

Let's assume without proof that Glibc developers are good. Similarly, kernel.org developers are good as are the gcc.gnu.org people. Should glibc, gcc and the kernel be in a monorepo? (Cue laugh track ...)

dboreham 7y ago
Did you just invent the unikernel?
- teddyh 7y ago
  AFAIK, Unix did this, so BSD Unix did this, and the modern BSD derivatives still do this.
NikkiA 7y ago
This is the red tinged future linux is headed towards anyway.
sally1620 7y ago
That is actually one of the advantages of the BSDs. Kernel and base system are in one repo and released together. It simplifies development and testing. and an easier upgrade for end-users.

scarejunba 7y ago

You're just pushing your trouble into a shadow layer that's hidden. You still have just as much complexity. It's just not encoded. If branch A on repo X will only work with branch B on repo Y, you're holding that relationship in an uncoded way. It's true and unrepresented, and you never want that.

reilly3000 7y ago

I think the whole idea of simplicity vs complexity, and the linked article "Worse is Better" is fundamentally ill-conceived. Simple vs. Complex is contextually relative. Literally every observer is subject to their own opinion of a design. Success in the wild = success. I think success in the wild, especially in our age of information overload, depends on being "convenient to understand and operate". A 'simple' solution may not be easy to grok. Few people think at the level of axioms. A survivable solution must be passed along to many people across generations. For some, monorepos are simple because that is what they know, for others multirepos are the norm. The survival of the firms that adopt these strategies will somewhat dictate what repo strategy propagates in the world, not the best design.

dboreham 7y ago

Always makes me think of a philips radio my Dad told me about called the "Mono Knob". It had a complex design that allowed control via just one knob. He said they were always in the shop for repair when he worked as a teenager in a radio store. https://www.thevalvepage.com/radios/philips/785ax/785ax.htm https://www.thevalvepage.com/radios/philips/785ax/785ax.htm

mark_l_watson 7y ago

My primary language now is Common Lisp and I have one mother of all mono repos for all of my personal Common Lisp code. I set the root of this repo as a Quicklisp load point so all my libraries and applications are available with a Quicklisp load. Life is good. I don’t quite get the point of this article though. I am a very enthusiastic but not rockstar programmer, and I don’t have problems with a large mono repo.

drewm1980 7y ago
He is talking about big teams.
gumby 7y ago
But you're one person. The article argues that a single repo is unmanageable when you have many devs working at the same time.

jnurmine 7y ago

Is the monorepo/multirepo choice really the most important thing to consider? Branching: monorepo or not, if a feature-incomplete development branch for one of the supported targets can "hold the entire organization as a hostage" then the SCM people, and/or persons responsible of the SCM policy, should do some introspection... Why are deliveries done from a branch which is obviously still in development? Why does code-to-be-released need to depend on incomplete work? Why aren't something like "topic branches" used? Modularity: monorepo or not, problems will certainly appear when the complexity of implementation outpaces the capacity created by the design. To get modularity, one needs actual modules with properly designed (=not brittle, DRY, KISS, YAGNI, SOLID, etc. etc.) interfaces between the modules. Now, does monorepo/multirepo really play a role here at all? If everyday changes are constantly modifying the module interfaces in incompatible ways which breaks existing code, this speaks something about the design, or rather the insufficiency of it. Of course, every project and team is different. However, even if a locally optimal choice for the monorepo vs. multirepo question is found, problems existing regardless of monorepo/multirepo will still be there.

jknoepfler 7y ago
I was wondering the same thing. Like, I use a microservice architecture at work, but the choice of using one vs. many git repos to represent diffs in those services over time seems largely meaningless. I don't like large diffs or people breaking production, but this is solved by testing and insisting upon small diffs, not by how many git repos we use. Formally speaking, multi-repo management allows a strict subset of the diffs allowed to a mono-repo (because diffs can 't extend beyond each repo root). Are the excluded possibilities all bad? No. Are they generally bad? Not really. Are they sometimes bad? Sure. Are they sometimes better than many diffs across many repos? Sure. Can a reasonably competent dev team tell the difference? Sure, usually. Unsurprisingly, this usually requires the exact same tooling as ensuring the quality of microrepo changes. If you're continuously deploying master, have a healthy ci/cd pipeline, and enforce good merging discipline, you're fine either way. I'm a little tired of doing things like revving our trace and logging libraries across our 50+ micro repos that represent microservices. That's genuinely obnoxious. Is it bad? No. Is it obviously more or less error prone than the equivalent monorepo update? No. All the bad bits of either strategy just require some tooling and a clear head.

jayd16 7y ago

>bad fork How is this an argument? You merge the unforked projects and its the equivalent to multirepo. I don't follow the argument at all. ...I started writing rebuttals to the others but I guess when your argument is "yeah you can do it right but you _could_ do it wrong and I have defined the question in such a way that we err on success for multi-repo and err on failure on mono-repo" I can't really fight that.

ThePhysicist 7y ago

Does anyone here have experience using submodules to tie individual repositories together? We've been using this in our small startup (only a few developers) and so far it works nicely. It allows us to check out and develop repositories individually but at the same time maintain an exact dependency graph for our entire system. You can for example have a single repository that ties together different projects and has submodules that contain specific references e.g. to the frontend, backend and deployment repositories. You can then use this master repository e.g. for deployment and integration testing. Gitlab makes CI/CD in such a setup very easy and checks out submodules recursively during a build, even across groups. The drawback is that not many people are familiar with submodules and they can be a bit tedious to set up, though working with a submodule is almost like working with a normal file in git. One danger is of course that branching between individual submodules can get messy. Another nuisance might be that you have to commit recursively, i.e. if you have one repository with a submodule to which you make changes you need to first commit these changes in the submodule and then create a new commit in the parent repository that adds the new version of the submodule. Maybe this is a good thing though as it forces you to commit changes individually in each submodule before committing a larger change into your main repository. In general I would avoid nesting submodules more than two levels deep, as this can quickly get confusing. In the past I've also worked on a large mono-repositoriy and enjoyed it as well, just curious to hear if anybody has used submodules in a larger team.

zaphod12 7y ago
Yes, I have experience and it has always seemed a great idea with a handful of developers and then come back to be a disaster when the team scaled. They become a nightmare to keep everything properly up to date when you have a lot of people working on all of it. Git sub repos worked a bit better, but overall I really recommend submodules exclusively when the submoduled repo changes very infrequently.
the_gipsy 7y ago
I have bad experiences with submodules. It was only one submodule just one level deep, and it only contained something like a convoluted configuration shared among multiple repos. As you say, getting a change first into the child and then into the parent requires double PRs and testing. But that's the same as if you had it as a package dependency. Only that instead of a version, you have a sha1 which you never know what it is. I prefer package dependency, because it forces you to explicitly make a release, where it should have passed PR and some integration tests. Also merge conflicts are clearer.

jupp0r 7y ago

There is also a way to simultaneously reap the drawbacks of monorepos and multirepos: consolidate numerous small repos into somewhat big monorepos and then don't merge everything into one big repo. This way, you'll have to deal with * difficult tooling * dependency hell between the mono repos (which are now way more tightly coupled due to the dependency graph between them being denser) * long living branches causing way more collateral damage as described in the original article * cross-repo changes have become even harder for all the reasons above You get all the bad things and avoid those advantages! Welcome to my world :)

galkk 7y ago

I've experienced 3 large codebases with different approaches: 1. Monorepo: Google3 2. Non monorepo, large pile of #@$: Microsoft Exchange 3. Non monorepo, Amazon After working with them, from my personal experience, monorepo was the best. Yes, Google has ton of internal stuff and they could go away with not using much of external dependencies, but when everything works, it works like a charm. Convenience of defining protobufs/contracts, ease of reference them and ton of the things are given to you when you're in the system. At Google I never felt that the system is hostile to you. It was extremely easy to start hacking something if you'd like to. Yes, it's not only monorepo, but the overall quality of the tools available, but monorepo is also quite a significant part of it.

rosstafarian0 7y ago

Is being demeaning and rigid just the cool thing to do today in blogs. I feel like I keep reading articles like this every day now. "Well if your team is full of dumbasses" or "If you use OO instead of functional programming"

NikkiA 7y ago
Have you not noticed that this is the new norm everywhere?

lootsauce 7y ago

I feel like I’m missing something. Never used monorepo before but looking into it for our node code base. It seems like the combination of a monorepo and individually publishing the packages to a private npm server such as nexus eliminates many of these issues. One project can remain using an older version while another can use a breaking change. Pin your versions and follow semver and you should be fine. What am I missing here?

sally1620 7y ago

What author misses is that multi-repo is also not dumbass proof. Our team of about 60 people owned about 5-6 git repos that compiled into one SO. Every simple bug fix required multiple diffs to multiple repos. The real argument that the author is making is that worse is better. Monorepo requires good tooling and a disciplined team. Multi-repo is worse but it is easier to manage when dealing with inexperienced programmers who want to have their own repo for their shiny little microservice. IMO, the difference is that multi-repo has limitations and mono-repo has challenges. You will never get atomic commits and precise versioning in multi-repo. With mono-repo, there are a lot of challenges that can be solved with good engineering.

epage 7y ago

This reminds me of some the trade-offs I've looked at with monorepos: https://epage.github.io/dev/monorepos/ https://epage.github.io/dev/monorepos/

hinkley 7y ago

One of the tenets of XP that survived (or should I say, is amplified?) into CI/CD is the idea that you should build up callouses for painful activities instead of trying to avoid them. In that context, if a thing is tough but has value, you make a path to it. First make the tools consistent, and then make people consistently use the tools. The more predictable the system becomes (predictability is the opposite of magic!), the more you insist on people using it. Pushback is a kind of feedback, and you have to address at least some of the concerns of people who refuse ('meet me halfway here'). Someday it will shock no-one to say that Git is not the best of all possible version control tools. If this is difficult, it may not be the people. Maybe it's time to start thinking about the next version control system? SVN had some pretty decent facilities for monorepos. Some people will tell you that Git traded some of these features for others, but looking through the information architecture documentation for git, I don't think I can agree. Some of that information is there, it's just maybe not packaged for consumption.

hinkley 7y ago

> In a Good team, you don't have multiple concurrent branches from which actual product deliveries are produced, and/or where most people get to maintain these branches simultaneously for a long time. These sorts of Black and White, naked assertions drive me nuts. Buried in this statement is an assumption that the only software model worth even discussing is SaaS software - all copies of the code being run are run by your team, so master@HEAD is our ground truth at all times (except during deployments, which BTW are happening at least 10 minutes out of every hour of every day...) Teams that sell applications or allow self-hosting, or even some SaaS shops with large enough customers are going to have to maintain multiple release branches. Possibly for years. From personal experience, anything above 3 seems to become unsustainable. But having 3 repos (a monorepo with 2 active branches + master) may be the right answer for you. One can't work, and 100 is murder. Stop the pendulum in the middle.