Optimized Dockerfile for Rust

Below is a simple Dockerfile for a Rust project. It uses a multi-stage build to first build the project and then copy the binary into a new image. This is a common pattern for compiled languages.

The first stage is named builder. It caches the dependencies with a dummy src/main.rs file. This allows the dependencies to be cached and reused when the source code changes.

# Build dependencies
COPY Cargo.toml Cargo.lock ./
RUN mkdir ./src && echo 'fn main() {}' > ./src/main.rs
RUN cargo build --release

The main.rs file is then deleted and the real source code is copied in. This forces the build to recompile the source code, but not the dependencies.

# Replace with real src
RUN rm -rf ./src
COPY ./src ./src
# break the Cargo cache
RUN touch ./src/main.rs
# Build the project
RUN cargo build --release

The run stage uses the debian:bookworm-slim image which is a minimal Debian image. The bookworm tag is the codename for the next Debian release. The -slim tag is a minimal version of the image.

# Run stage
FROM debian:bookworm-slim as run
RUN apt-get update && apt install -y openssl && rm -rf /var/lib/apt/lists/* && apt-get clean
COPY --from=builder /usr/src/app/target/release/app /usr/local/bin
ENTRYPOINT ["/usr/local/bin/app"]

The full Dockerfile is below.

# Build stage
FROM rust:bookworm as builder
WORKDIR /usr/src/app
# Build dependencies
COPY Cargo.toml Cargo.lock ./
RUN mkdir ./src && echo 'fn main() {}' > ./src/main.rs
RUN cargo build --release
# Replace with real src
RUN rm -rf ./src
COPY ./src ./src
# break the Cargo cache
RUN touch ./src/main.rs
# Build the project
RUN cargo build --release
# Run stage
FROM debian:bookworm-slim as run
RUN apt-get update && apt install -y openssl && rm -rf /var/lib/apt/lists/* && apt-get clean
COPY --from=builder /usr/src/app/target/release/app /usr/local/bin
ENTRYPOINT ["/usr/local/bin/app"]