Dockerfile

FROM --platform=${BUILDPLATFORM} rust:1.84.0@sha256:e6e40c05cfe7dd55ad13794333d31b6d0818f0c6086876e7dc65871e6c8c0b21 AS rust-base

ARG APPLICATION_NAME

RUN rm -f /etc/apt/apt.conf.d/docker-clean \
    && echo 'Binary::apt::APT::Keep-Downloaded-Packages "true";' >/etc/apt/apt.conf.d/keep-cache

# borrowed (Ba Dum Tss!) from
# https://github.com/pablodeymo/rust-musl-builder/blob/7a7ea3e909b1ef00c177d9eeac32d8c9d7d6a08c/Dockerfile#L48-L49
RUN --mount=type=cache,id=apt-cache-amd64,target=/var/cache/apt,sharing=locked \
    --mount=type=cache,id=apt-lib-amd64,target=/var/lib/apt,sharing=locked \
    apt-get update && \
    apt-get --no-install-recommends install -y \
    build-essential \
    musl-dev \
    musl-tools

FROM rust-base AS rust-linux-amd64
ARG TARGET=x86_64-unknown-linux-musl

FROM rust-base AS rust-linux-arm64
ARG TARGET=aarch64-unknown-linux-musl
RUN --mount=type=cache,id=apt-cache-arm64,from=rust-base,source=/var/cache/apt,target=/var/cache/apt,sharing=locked \
    --mount=type=cache,id=apt-lib-arm64,from=rust-base,source=/var/lib/apt,target=/var/lib/apt,sharing=locked \
    dpkg --add-architecture arm64 && \
    apt-get update && \
    apt-get --no-install-recommends install -y \
    libc6-dev-arm64-cross \
    gcc-aarch64-linux-gnu

FROM rust-${TARGETPLATFORM//\//-} AS rust-cargo-build

RUN rustup target add ${TARGET} && rustup component add clippy rustfmt

# The following block
# creates an empty app, and we copy in Cargo.toml and Cargo.lock as they represent our dependencies
# This allows us to copy in the source in a different layer which in turn allows us to leverage Docker's layer caching
# That means that if our dependencies don't change rebuilding is much faster
WORKDIR /build
RUN cargo new ${APPLICATION_NAME}
WORKDIR /build/${APPLICATION_NAME}
COPY .cargo ./.cargo
COPY Cargo.toml Cargo.lock ./

RUN --mount=type=cache,target=/build/${APPLICATION_NAME}/target \
    --mount=type=cache,id=cargo-git,target=/usr/local/cargo/git/db,sharing=locked \
    --mount=type=cache,id=cargo-registery,target=/usr/local/cargo/registry/,sharing=locked \
    cargo build --release --target ${TARGET}

FROM rust-cargo-build AS rust-build

WORKDIR /build/${APPLICATION_NAME}

# now we copy in the source which is more prone to changes and build it
COPY src ./src

# ensure cargo picks up on the change
RUN touch ./src/main.rs

# --release not needed, it is implied with install
RUN --mount=type=cache,target=/build/${APPLICATION_NAME}/target \
    --mount=type=cache,id=cargo-git,target=/usr/local/cargo/git/db,sharing=locked \
    --mount=type=cache,id=cargo-registery,target=/usr/local/cargo/registry/,sharing=locked \
    cargo install --path . --target ${TARGET} --root /output

FROM alpine:3.21.2@sha256:56fa17d2a7e7f168a043a2712e63aed1f8543aeafdcee47c58dcffe38ed51099

ARG APPLICATION_NAME

RUN addgroup -S appgroup && adduser -S appuser -G appgroup
USER appuser

WORKDIR /app

COPY --from=rust-build /output/bin/* /app/entrypoint

ENV RUST_BACKTRACE=full
ENTRYPOINT ["/app/entrypoint"]