Monorepo

A Monorepo is a version control repository that houses the code for multiple projects within a single repository, promoting ease of collaboration and consistency across the projects.

• Context:
  • It can (typically) centralize the development of multiple interrelated projects, facilitating easier code sharing and reuse.
  • It can (often) streamline dependency management and versioning by maintaining all dependencies within the same repository.
  • It can range from being a repository for small, tightly-coupled projects to one for large-scale, diverse codebases used by major technology companies.
  • It can help in maintaining consistent coding standards and tools across all projects within the monorepo.
  • It can pose challenges in scaling the build system and version control mechanisms as the codebase grows.
  • ...
• Example(s):
  • an instance where Google employs a monorepo to manage a vast codebase, allowing for extensive code reuse and unified development practices.
  • an example where Facebook utilizes a monorepo to handle the rapid development and deployment of features across its various applications.
  • a scenario where Microsoft uses a monorepo for its internal projects, ensuring consistency and shared tooling across different development teams.
  • a case where Uber maintains a monorepo to manage its diverse software projects, enhancing collaboration and code visibility.
  • an application where Airbnb uses a monorepo to streamline its development processes and maintain a cohesive codebase.
  • ...
• Counter-Example(s):
  • Multirepos, which separate different projects into distinct repositories, can sometimes reduce complexity in version control but may lead to challenges in managing dependencies and consistency across projects.
  • Microservice Architectures often employ multiple repositories for different services to maintain independent deployment cycles and scaling.
• See: Version Control, Revision Control, Repository (Version Control), Monolithic_application, Google, Facebook, Microsoft, Uber, Airbnb, Twitter, Build System.

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References

2024

• Perplexity
  • Monorepos have several pros and cons that should be carefully considered before adoption. Here are some key points:
  • Pros of Monorepos
    1. **Simplified Dependency Management**: All projects use the same versions of dependencies, reducing conflicts and making updates easier [1][4][13][17].
    2. **Atomic Commits**: Changes across multiple projects can be made atomically in a single commit, enabling large-scale refactoring [1][4][13][17][18].

3. **Better Collaboration**: Increased visibility into the entire codebase fosters collaboration and code sharing across teams [1][4][8][13][16][17].

4. **Consistent Tooling**: Common tooling, linting, testing frameworks can be applied consistently across all projects [1][3][4][10][13].

5. **Simplified Builds**: A unified build process can be used for all projects, simplifying CI/CD setup [1][3][9][16].

6. **Easier Navigation**: Navigating and understanding relationships between projects is easier in a monorepo [18].

• • Cons of Monorepos
    1. **Performance Issues**: Operations like `git status`, `git blame` can become slow as the repo grows in size [1][5][9][13][17].
    2. **Build Times**: Without proper tooling, building the entire repo for small changes can be inefficient [1][3][13][17].

3. **Restricted Access**: Providing granular access controls for different teams/projects within a monorepo can be challenging [1][7][17].

4. **Steep Learning Curve**: Navigating and understanding a large, unified codebase can be daunting for new developers [7][13].

5. **Coupling Risk**: Tight coupling between projects is easier, which can lead to architectural issues if not carefully managed [1][7][12][18].

6. **Broken Builds**: If the main branch build is broken, it affects everyone until it's fixed [9][17].

7. **Tooling Needs**: Additional tooling and infrastructure may be required to effectively manage a large monorepo [3][7][13][17].

• • In summary, monorepos offer significant benefits for large codebases with many interdependent projects by improving collaboration, consistency, and maintainability. However, they also introduce challenges around performance, access control, and the need for robust tooling as the codebase scales [1][3][4][7][13][17]. The decision should carefully weigh the trade-offs based on the specific needs and constraints of the project and organization.
  • Citations:

[1] https://livecycle.io/blogs/monorepos/
[2] https://www.reddit.com/r/devops/comments/1815x7i/what_is_monorepo_and_what_are_the_best_practices/
[3] https://buildkite.com/blog/monorepo-ci-best-practices
[4] https://nx.dev/concepts/decisions/why-monorepos
[5] https://graphite.dev/guides/git-monorepo-best-practices-for-scalability
[6] https://graphite.dev/guides/monorepo-pros-and-cons
[7] https://www.thoughtworks.com/en-us/insights/blog/agile-engineering-practices/monorepo-vs-multirepo
[8] https://content.red-badger.com/resources/the-key-advantages-of-using-a-monorepo
[9] https://semaphoreci.com/blog/what-is-monorepo

2020

• (Wikipedia, 2020) ⇒ https://en.wikipedia.org/wiki/Monorepo Retrieved:2020-10-1.
  • In revision control systems, a monorepo ("mono" from Greek μόνος, mónos, 'single, alone' and "repo" short for repository) is a software development strategy where code for many projects is stored in the same repository. some forms of this software engineering practice were over a decade old, but the general concept had only recently been named. Many attempts have been made to differentiate between monolithic applications and other, newer forms of monorepos.

     Google, Facebook, Microsoft, Uber, Airbnb and Twitter all employ very large monorepos with varying strategies to scale build systems and version control software with a large volume of code and daily changes.

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