Bazel (software)

Bazel (software)
Name	Bazel
Developer	Google
Released	2015
Programming language	Java, Python, C++
Operating system	Linux, macOS, Windows
License	Apache License 2.0

Bazel (software) Bazel is a build and test tool originally developed at Google and later released as an open source project. It provides an incremental, hermetic build system intended for large monorepos and continuous integration environments used by organizations such as Uber Technologies, Stripe, Pinterest, Dropbox, and Airbnb. Bazel integrates with languages and ecosystems including Java (programming language), C++, Python (programming language), Go (programming language), Android (operating system), and Kotlin, supporting reproducible builds for complex, multi-language codebases.

History

Bazel began inside Google as a successor to internal systems influenced by Blaze (software), evolving amid build engineering efforts tied to projects like MapReduce, Gmail, YouTube, and Android (operating system). The project was publicly announced and open sourced in 2015, following precedents set by other corporate open source releases such as Chromium and TensorFlow. Early development involved contributors from organizations including Red Hat, Intel, Oracle Corporation, IBM, and Google engineers who had worked on Google Chrome and Google App Engine. Bazel's roadmap and governance attracted attention from foundations like The Linux Foundation and communities around Apache Software Foundation projects, and it has been discussed at conferences such as Google I/O, KubeCon, PyCon, and Jenkins World.

Design and architecture

Bazel's architecture emphasizes correctness, hermeticity, and parallelism drawing conceptual links to prior systems like Make (software), Ninja (build system), and Buck (build system). The core is implemented in Java (programming language), with components in C++ for performance and Python (programming language) for tooling, echoing multi-language projects such as LLVM and Chromium. Bazel uses a content-addressable cache inspired by Git and Content-addressable storage patterns seen in Docker (software) and Bazaar (software), and supports remote execution protocols related to gRPC and Remote Procedure Call. The design supports sandboxing approaches similar to Seccomp, cgroups, and Namespaces (Linux), while its dependency graph handling resembles algorithms from DAG (graph theory) research and tools like Apache Maven and Gradle.

Build language and rules

Bazel defines build files using a Starlark dialect that descends from Python (programming language), influenced by configuration approaches used in GNU Autotools, CMake, and SCons (software). Starlark enables rule authors to describe Java (programming language) targets, C++ toolchains, Android (operating system) binaries, and Go (programming language) modules, analogous to plugins for Apache Ant and extensions for Gradle. Community-maintained rule sets include integrations like rules_kotlin, rules_python, rules_go, and ecosystem projects comparable to Maven Central and npm (software). The rule API supports custom actions and toolchains similar in purpose to extensibility in Bazelisk usage and parallels with Buck (build system)'s rule model.

Ecosystem and integrations

Bazel integrates with IDEs and CI systems such as IntelliJ IDEA, Visual Studio Code, Eclipse, Bazelisk, Jenkins (software), Travis CI, CircleCI, GitHub Actions, and GitLab CI/CD. Language integrations span Java (programming language), Kotlin, Scala (programming language), C#, Rust (programming language), and Swift (programming language), often via community rule sets and plugins similar to those for Gradle and Maven (software). Mobile and platform tooling interoperates with Android Studio, Xcode, Firebase, and Protobuf, and remote execution leverages services compatible with Kubernetes, Google Cloud Platform, Amazon Web Services, and Microsoft Azure. The project ecosystem includes package registries and tooling analogues like Bazel Central Registry and resources comparable to Homebrew and Chocolatey (package manager).

Performance and scalability

Bazel emphasizes parallel builds, incremental rebuilds, and remote caching to achieve performance at scale comparable to systems used in Google and elsewhere, drawing on research exemplified by Make (software) optimizations and distributed systems practices seen in MapReduce. Measurements cited by practitioners compare Bazel's throughput to alternatives such as Gradle and Buck (build system), with remote execution and caching models influenced by Content-addressable storage and HTTP/2 transport work in gRPC. Scalability case studies reference large monorepos like those maintained at Google, Facebook, Microsoft, and Uber Technologies; Bazel's incremental analysis and action execution are designed to reduce rebuild times in CI pipelines such as Jenkins (software) and GitHub Actions.

Adoption and use cases

Bazel is used by companies and projects for monorepo management, continuous integration, and multi-language builds, with adopters including Google, Stripe, Pinterest, Uber Technologies, Dropbox, Airbnb, Square (company), and Twitter. Open source projects and foundations integrate Bazel for reproducible builds in repositories tied to TensorFlow, Envoy (software), Istio, gRPC, and Kubernetes-adjacent tooling. Use cases span mobile app development with Android (operating system) and iOS, server-side systems in Java (programming language), Go (programming language), and C++, embedded systems workflows similar to those in Zephyr Project and Yocto Project, and continuous delivery pipelines using Spinnaker and Argo CD.

Category:Build automation