cargo-chefwas initially developed for the deployment chapter of Zero to Production In Rust, a hands-on introduction to backend development using the Rust programming language.
You can install cargo-chef from crates.io with
bash
cargo install cargo-chef --locked
:warning: cargo-chef is not meant to be run locally
Its primary use-case is to speed up container builds by running BEFORE the actual source code is copied over. Don't run it on existing codebases to avoid having files being overwritten.
cargo-chef exposes two commands: prepare and cook:
bash
cargo chef --help
```text
cargo-chef
USAGE:
cargo chef
SUBCOMMANDS:
cook Re-hydrate the minimum project skeleton identified by cargo chef prepare and
build it to cache dependencies
prepare Analyze the current project to determine the minimum subset of files (Cargo.lock
and Cargo.toml manifests) required to build it and cache dependencies
```
prepare examines your project and builds a recipe that captures the set of information required to build your dependencies.
bash
cargo chef prepare --recipe-path recipe.json
Nothing too mysterious going on here, you can examine the recipe.json file: it contains the skeleton of your project (e.g. all the Cargo.toml files with their relative path, the Cargo.lock file is available) plus a few additional pieces of information.
In particular it makes sure that all libraries and binaries are explicitly declared in their respective Cargo.toml files even if they can be found at the canonical default location (src/main.rs for a binary, src/lib.rs for a library).
The recipe.json is the equivalent of the Python requirements.txt file - it is the only input required for cargo chef cook, the command that will build out our dependencies:
bash
cargo chef cook --recipe-path recipe.json
If you want to build in --release mode:
bash
cargo chef cook --release --recipe-path recipe.json
You can also choose to override which Rust toolchain should be used. E.g., to force the nightly toolchain:
bash
cargo +nightly chef cook --recipe-path recipe.json
cargo-chef is designed to be leveraged in Dockerfiles:
```dockerfile FROM lukemathwalker/cargo-chef:latest-rust-1 AS chef WORKDIR /app
FROM chef AS planner COPY . . RUN cargo chef prepare --recipe-path recipe.json
FROM chef AS builder COPY --from=planner /app/recipe.json recipe.json
RUN cargo chef cook --release --recipe-path recipe.json
COPY . . RUN cargo build --release --bin app
FROM debian:buster-slim AS runtime WORKDIR /app COPY --from=builder /app/target/release/app /usr/local/bin ENTRYPOINT ["/usr/local/bin/app"] ```
We are using three stages: the first computes the recipe file, the second caches our dependencies and builds the binary, the third is our runtime environment.
As long as your dependencies do not change the recipe.json file will stay the same, therefore the outcome of cargo chef cook --release --recipe-path recipe.json will be cached, massively speeding up your builds (up to 5x measured on some commercial projects).
We offer lukemathwalker/cargo-chef as a pre-built Docker image equipped with both Rust and cargo-chef.
The tagging scheme is <cargo-chef version>-rust-<rust version>.
For example, 0.1.22-rust-1.56.0.
You can choose to get the latest version of either cargo-chef or rust by using:
- latest-rust-1.56.0 (use latest cargo-chef with specific Rust version);
- 0.1.22-rust-latest (use latest Rust with specific cargo-chef version).
You can find all the available tags on Dockerhub.
:warning: You must use the same Rust version in all stages
If you use a different Rust version in one of the stages caching will not work as expected.
If you do not want to use the lukemathwalker/cargo-chef image, you can simply install the CLI within the Dockerfile:
```dockerfile FROM rust:1 AS chef
RUN cargo install cargo-chef WORKDIR app
FROM chef AS planner COPY . . RUN cargo chef prepare --recipe-path recipe.json
FROM chef AS builder COPY --from=planner /app/recipe.json recipe.json
RUN cargo chef cook --release --recipe-path recipe.json
COPY . . RUN cargo build --release --bin app
FROM debian:buster-slim AS runtime WORKDIR app COPY --from=builder /app/target/release/app /usr/local/bin ENTRYPOINT ["/usr/local/bin/app"] ```
If you want to run your application using the alpine distribution you need to create a fully static binary.
The recommended approach is to build for the x86_64-unknown-linux-musl target using muslrust.
cargo-chef works for x86_64-unknown-linux-musl, but we are cross-compiling - the target
toolchain must be explicitly specified.
A sample Dockerfile looks like this:
```dockerfile
rust-musl-builder as base image, instead ofFROM clux/muslrust:stable AS chef USER root RUN cargo install cargo-chef WORKDIR /app
FROM chef AS planner COPY . . RUN cargo chef prepare --recipe-path recipe.json
FROM chef AS builder COPY --from=planner /app/recipe.json recipe.json
RUN cargo chef cook --release --target x8664-unknown-linux-musl --recipe-path recipe.json COPY . . RUN cargo build --release --target x8664-unknown-linux-musl --bin app
FROM alpine AS runtime RUN addgroup -S myuser && adduser -S myuser -G myuser COPY --from=builder /app/target/x86_64-unknown-linux-musl/release/app /usr/local/bin/ USER myuser CMD ["/usr/local/bin/app"] ```
cargo-chef has been tested on a few OpenSource projects and some of commercial projects, but our testing has definitely not exhausted the range of possibilities when it comes to cargo build customisations and we are sure that there are a few rough edges that will have to be smoothed out - please file issues on GitHub.
cargo-chef:A common alternative is to load a minimal main.rs into a container with Cargo.toml and Cargo.lock to build a Docker layer that consists of only your dependencies (more info here). This is fragile compared to cargo-chef which will instead:
Dockerfile using the "manual" approachcargo cook and cargo build must be executed from the same working directory. If you examine the *.d files under target/debug/deps for one of your projects using cat you will notice that they contain absolute paths referring to the project target directory. If moved around, cargo will not leverage them as cached dependencies;cargo build will build local dependencies (outside of the current project) from scratch, even if they are unchanged, due to the reliance of its fingerprinting logic on timestamps (see this long issue on cargo's repository);Licensed under either of Apache License, Version 2.0 or MIT license at your option. Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in this crate by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.