Bazel vs Gradle: What are the differences?

Comparison between Bazel and Gradle

1. Build Language and Configuration: Bazel uses its own language called Starlark for build configuration, which is a Python-based DSL (Domain-Specific Language). On the other hand, Gradle uses Groovy or Kotlin for build configuration, providing a more flexible and expressive language for developers.

2. Build Performance: Bazel is known for its emphasis on build speed and scalability. It uses a distributed caching mechanism and an intelligent target dependency graph to parallelize builds effectively, resulting in faster incremental builds. In contrast, Gradle's performance may vary depending on the build complexity and customization, but it provides more flexibility in terms of plugin ecosystem and build customization.

3. Build Reproducibility: Bazel guarantees build reproducibility by enforcing hermetic builds. It ensures that builds are isolated from external factors, such as system environment and toolchain updates, resulting in consistent and deterministic builds. While Gradle supports reproducibility through its build caching feature, it does not enforce strict hermeticity by default, allowing more flexibility but potentially introducing variations in build outputs.

4. Build Ecosystem: Bazel has a more limited plugin ecosystem compared to Gradle. Although Bazel provides a plugin system, the number of available plugins is relatively smaller compared to Gradle's extensive plugin ecosystem. Gradle offers a wide range of community and official plugins, which can be easily integrated into the build process, adding additional functionality and convenience.

5. Build Scale and Monorepo Support: Bazel is designed for large-scale projects and monorepo setups, where multiple projects are combined into a single repository. It excels in handling complex and interconnected project structures, allowing fine-grained control over dependencies and incremental build optimizations. Gradle, while also capable of handling monorepos, may face performance challenges when dealing with large-scale projects due to its underlying design differences.

6. Interoperability and Integration: Gradle has better integration with existing build systems and IDEs, making it easier to adopt and migrate existing projects. It has a more established presence in the Java ecosystem and supports various languages and frameworks out of the box. Bazel, although gaining popularity, may require additional effort to integrate with existing tools and frameworks, especially in non-Java ecosystems.

In Summary, Bazel and Gradle have distinguishing characteristics in terms of build language, performance, reproducibility, ecosystem, scalability, and interoperability. The choice between them depends on the specific requirements and context of the project, considering factors such as build complexity, scale, and existing toolchain integration.