Getting Started with Modern Bazel

Let's start by understanding what makes Bazel different from traditional build systems.

Why Bazel?

Traditional build systems typically require:

1. Language-Specific Solutions:

   • Different dependency managers (npm, pip, maven)
   • Different build tools (webpack, setuptools, gradle)
   • Different test runners

2. OS-Specific Configuration:

   • Different package managers (apt, yum, brew)
   • Different environment setup
   • Different build commands

This leads to:

• Inconsistent builds across environments
• Complex setup instructions
• Dependency version conflicts
• Non-reproducible builds

Bazel solves these problems with a unified approach:

1. Universal Dependency Management:

   • Language-agnostic module system
   • Centralized registry for verified modules
   • Local and remote caching

2. Unified Build System:

   • Language-specific rules but unified execution
   • Cached, incremental builds
   • Parallel execution

3. Hermetic Build Environment:

   • Reproducible builds across machines
   • Explicit toolchain management
   • Controlled build inputs

Getting Started

Installing Bazel with Bazelisk

The recommended way to install and manage Bazel is through Bazelisk, a version manager that automatically downloads and runs the correct version of Bazel for your project.

Prerequisites:

• A supported operating system (Linux, macOS, or Windows)
• One of:
  • npm (recommended)
  • Go
  • Homebrew (macOS)
  • Chocolatey (Windows)

Install Bazelisk using your preferred package manager:

# Using npm (recommended)
npm install -g @bazel/bazelisk

# Or using Go
go install github.com/bazelbuild/bazelisk@latest

Bazelisk will:

• Download the correct version of Bazel based on your project's .bazelversion file
• Keep your Bazel installation up to date
• Switch between different versions for different projects

Create Your First Project

1. Create a new directory and initialize it:

mkdir my-project && cd my-project
echo "7.4.0" > .bazelversion  # Pin Bazel version

2. Create MODULE.bazel:

module(
    name = "my_project",
    version = "0.1.0",
)

bazel_dep(name = "rules_python", version = "0.27.1")

3. Create a simple Python application:

main.py

def main():
    print("Hello from Modern Bazel!")

if __name__ == "__main__":
    main()

BUILD.bazel

load("@rules_python//python:defs.bzl", "py_binary")

py_binary(
    name = "hello",
    srcs = ["main.py"],
)

4. Build and run:

bazel run //:hello

Project Structure

A typical Bazel project structure:

my_project/
├── .bazelversion        # Pinned Bazel version
├── MODULE.bazel         # Module and dependency definitions
├── BUILD.bazel          # Build targets for the root package
├── main.py             # Source code
└── src/                # Additional source directories
    └── BUILD.bazel     # Build targets for src package

Next Steps

• Learn about Build Rules and how they work
• Understand Module Dependencies
• Explore the Core Concepts

Common Issues

1. Version Conflicts

   • Use compatible versions from the Bazel Central Registry
   • Check dependency documentation for version requirements

2. Build Failures

   • Verify rule usage in BUILD.bazel files
   • Check that all required dependencies are declared
   • Run bazel clean if you suspect cache issues

3. Module Not Found

   • Verify dependency versions exist in BCR
   • Check for typos in module names