bazel-rust-docker-example

This project is intended to demonstrate a Bazel setup for Rust services with Docker support.

It has the following features:

• 🏗 Bazel build system
• 🦀 Compile, test and run Rust binaries, libraries and tests
• 🧰 Cargo workspace and Cargo Raze for managing Rust dependencies
• 🧐 Support for Rust-analyzer (and VS Code)
• ⚖️ Optimized Rust compiler flags for release targets
• 📦 Minimal Docker Rust images with distroless/static-debian11 as base image (2.36MB)
• 🚀 CircleCI pipeline with Bazel remote-cache on AWS S3
• ⚙️ Support for cross-compiling Rust targets from MacOS to Linux using Musl

Prerequisites

• Install Bazelisk

• Install Rustup

• Install Cargo Raze

$ cargo install cargo-raze

• For cross-compilation from MacOS to Linux musl targets, install musl-cross

$ brew install filosottile/musl-cross/musl-cross

• For Bazel remote cache, install https://github.com/buchgr/bazel-remote

Bazel Commands

Build the entire project:

$ bazel build //...

Run all tests:

$ bazel test //...

Run service1 natively:

$ bazel run //service1:app

Run service1 within a Docker container:

$ bazel run //service1:image

⚠️ This only works when your host machine is Linux. Look for cross-compiling below when building on MacOS.

Run service1 within an optimzed release Docker container:

$ bazel run //service1:image --//:release

⚠️ This only works when your host machine is Linux. Look for cross-compiling below when building on MacOS.

Cross-compile service1 from MacOS to Linux and run within a Docker container:

$ bazel run //service1:image --platforms //build/platform:musl

Can also be combined with --//:release.

Rust-Analyzer

In order for Rust-Analyzer to work, it is necessary to generate a rust-project.json file. To do so, run

$ bazel run @rules_rust//tools/rust_analyzer:gen_rust_project

VS Code

When using VS Code as IDE, install the following extension for Rust-Analyzer: https://marketplace.visualstudio.com/items?itemName=matklad.rust-analyzer

In your VS Code settings.json, make sure to have the following configuration:

{ 
  "rust-analyzer.checkOnSave.overrideCommand": ["cargo", "check" "--message-format=json"]
}

The Rust-Analyzer extension will pick up the rust-project.json file which was generated earlier.

⚠️ Make sure to generate an updated rust-project.json file whenever a new folder or dependency is added. It may also be needed to reload the workspace when the updated structure is not immediately recognized by Rust-Analyzer.

Cargo Dependencies

For each of the dependencies listed in any of the Cargo.toml files, a Bazel build should be generated. This is done automatically by running

$ cargo raze

If not already the case, this will add a cargo folder in the root of the project. Crates can now be referenced fron within Bazel through //cargo/*NAME* (eg. //cargo/ferris_says).

Adding a new dependency

After adding a new external dependency in any of the Cargo.toml files, run the following steps:

1. Run cargo raze --generate-lockfile
2. Run bazel build //...
3. Update rust-project.json by running bazel run @rules_rust//tools/rust_analyzer:gen_rust_project
4. Reload Rust Workspace in VS Code
5. Start using crate in your Rust library or binary

Cross-compiling

This project provides a basic setup for cross-compiling from MacOS to Linux. The setup is inspired by rust-bazel-cross.

⚠️ A known limitation is that dependencies relying on macros fail to compile. More info here.

Bazel remote-cache

When applying the Bazel config flag --config=remote_cache, Bazel will connect to a remote cache running at localhost:9090. This server will sync files between a local cache and an AWS S3 bucket.

To start the bazel-remote server, run the script ./scripts/start_bazel_remote.sh. Provide the following environment variables:

• AWS_REGION
• AWS_ACCESS_KEY_ID
• AWS_SECRET_ACCESS_KEY
• AWS_S3_BUCKET_BAZEL_CACHE

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