OpenRaft: Why Vendored Instead Of Cargo Dependency?

Hey guys! Ever wondered why OpenRaft isn't just a regular dependency listed neatly in your Cargo.toml file, but instead, it's vendored? Well, let's dive into the nitty-gritty details and explore the reasons behind this design choice. Understanding why OpenRaft takes this approach can shed light on some important aspects of Rust development, dependency management, and the specific needs of projects like Octopii. So, buckle up, and let's get started!

What Does "Vendored" Mean?

Before we delve into the specifics, let's clarify what "vendored" actually means. In the context of Rust and Cargo, vendoring refers to the practice of copying the source code of a dependency directly into your project's source tree, rather than relying on Cargo to download and manage it from a crate registry like crates.io. When a crate is vendored, it essentially becomes a part of your project. This means you have a local copy of the code, and your project builds directly against this local copy.

This approach is in contrast to the more common method where you declare a dependency in your Cargo.toml file, and Cargo automatically fetches the required version from a registry, manages its compilation, and links it with your project. Vendoring might seem a bit old-school or even counterintuitive at first, especially given Cargo's excellent dependency management capabilities. However, it addresses certain specific challenges and offers unique advantages in particular scenarios. So, why would a project choose to vendor a dependency like OpenRaft?

Reasons for Vendoring OpenRaft

There are several compelling reasons why the Octopii project might choose to vendor OpenRaft instead of including it as a regular Cargo dependency. Let's explore these reasons in detail:

1. Reproducibility and Determinism

Reproducibility is a cornerstone of reliable software development. When you vendor a dependency, you ensure that your project always builds against the exact same version of the code, regardless of changes in the upstream crate registry. This is crucial for ensuring that your builds are deterministic, meaning that given the same source code and build environment, you will always get the same output.

Imagine a scenario where OpenRaft releases a new version with breaking changes, or worse, introduces a bug. If you were relying on Cargo to fetch the latest version, your project might suddenly break or exhibit unexpected behavior. By vendoring OpenRaft, you insulate yourself from these external changes. You have a known, working version of the code that you control. This can be particularly important for long-lived projects or applications where stability and predictability are paramount.

Furthermore, vendoring can protect against the "left-pad" problem, where a dependency is removed from the crate registry, causing builds to fail. While Cargo has mechanisms to mitigate this risk, vendoring provides an additional layer of security. You essentially create a local backup of the code, ensuring that your project can still be built even if the upstream crate disappears.

2. Control Over Dependencies

Vendoring gives you complete control over the dependency's code. You can modify it, patch it, or even fork it entirely to suit your specific needs. This level of control can be invaluable when you encounter a bug in the dependency that needs immediate attention, or when you require a feature that is not yet available in the upstream version. Instead of waiting for the maintainers of OpenRaft to address the issue or implement the feature, you can take matters into your own hands and make the necessary changes directly in your vendored copy.

However, this power comes with responsibility. When you modify a vendored dependency, you are responsible for maintaining those changes and merging them with future updates from the upstream project. This can add to your maintenance burden, but it also gives you the flexibility to adapt the dependency to your specific requirements.

3. Build Environment Consistency

Different environments can sometimes lead to different build outcomes due to variations in system libraries, compiler versions, or other environmental factors. By vendoring OpenRaft, you reduce the reliance on external factors during the build process. Everything required to build OpenRaft is included within your project, ensuring a more consistent build experience across different environments.

This is especially useful in scenarios where you have strict build requirements, such as when building for embedded systems or specialized hardware. Vendoring ensures that you can create a self-contained build environment that is isolated from the complexities and inconsistencies of the external world.

4. Security Considerations

While Cargo employs various security measures to ensure the integrity of crates, vendoring can provide an additional layer of security. By reviewing and auditing the vendored code, you can gain a better understanding of its inner workings and identify potential security vulnerabilities. This can be particularly important for projects that handle sensitive data or operate in security-critical environments.

However, it's important to note that vendoring does not automatically make your project more secure. You still need to carefully review and audit the code to identify and address potential vulnerabilities. Vendoring simply gives you more control over the security of your dependencies.

5. Licensing Compliance

Vendoring can also simplify licensing compliance. By including the source code of OpenRaft directly in your project, you can ensure that you have a clear understanding of the license under which it is distributed. This can be helpful for projects that need to comply with specific licensing requirements or restrictions.

However, it's important to remember that vendoring does not change the licensing terms of OpenRaft. You are still bound by the terms of the license, and you must ensure that you comply with all applicable requirements, such as including the original copyright notice and license text in your project.

Potential Drawbacks of Vendoring

While vendoring offers several advantages, it also comes with some potential drawbacks that need to be considered:

1. Increased Project Size

Vendoring increases the size of your project's source code repository, as you are including the entire source code of the dependency directly in your project. This can make your repository larger and more difficult to manage, especially for large dependencies like OpenRaft. Additionally, a larger repository can slow down cloning and other Git operations.

2. Maintenance Overhead

When you vendor a dependency, you are responsible for keeping it up to date with the latest version. This can be a time-consuming and error-prone process, especially if you have made modifications to the vendored code. You need to carefully merge your changes with the latest version of the upstream project and ensure that everything still works as expected. This can add significantly to your maintenance burden.

3. Code Duplication

Vendoring can lead to code duplication if multiple projects in your organization vendor the same dependency. This can waste disk space and make it more difficult to manage dependencies across your organization. It also increases the risk of inconsistencies between different versions of the dependency.

4. Build Time

Vendoring can increase build times, as the vendored code needs to be compiled as part of your project. This can be especially noticeable for large dependencies like OpenRaft. However, this can be mitigated by using techniques such as incremental compilation and caching.

Alternatives to Vendoring

If the drawbacks of vendoring outweigh the advantages, there are several alternatives that you can consider:

1. Cargo's [patch] Feature

Cargo's [patch] feature allows you to replace a dependency with a local copy or a modified version. This is similar to vendoring, but it does not require you to copy the entire source code of the dependency into your project. Instead, you can specify a patch that applies your changes to the original source code. This can be a more lightweight and maintainable alternative to vendoring.

2. Git Submodules

Git submodules allow you to include another Git repository as a subdirectory within your project. This is similar to vendoring, but it allows you to keep the dependency's code in a separate repository. This can be useful for managing large dependencies or dependencies that are shared between multiple projects.

3. Private Crates Registry

You can set up a private crates registry to host your own versions of dependencies. This gives you more control over the dependencies that are used in your projects and allows you to ensure that everyone is using the same versions. This can be a good option for organizations that have strict requirements for dependency management.

Conclusion

So, why is OpenRaft vendored instead of being a dependency in Cargo.toml? The answer lies in the desire for reproducibility, control, consistency, security, and licensing compliance. While vendoring has its drawbacks, it can be a valuable tool in certain situations, particularly when dealing with critical dependencies like OpenRaft. By understanding the reasons behind this design choice, you can make informed decisions about how to manage dependencies in your own Rust projects. Keep experimenting and keep learning, and you'll master these concepts in no time! Cheers, and happy coding!