Dockerfile

ARG APP_VERSION=0.0.0-SNAPSHOT
ARG APP_GID=5000
ARG APP_UID=5000
ARG ALPINE_VERSION=3.16
ARG RUST_VERSION=1.62.0


## Builder stage
FROM --platform=$BUILDPLATFORM alpine:$ALPINE_VERSION AS builder
WORKDIR /app

# Install Rust
RUN apk add --no-cache build-base rustup
ARG RUST_VERSION
RUN rustup-init --default-toolchain=$RUST_VERSION -y
ENV PATH="$PATH:/root/.cargo/bin"

# Fetch deps using dummy app
COPY Cargo.toml .
COPY Cargo.lock .
RUN mkdir src \
&& echo "fn main() {}" > src/main.rs \
&& cargo fetch \
&& rm -rf src/

# Build app
COPY src/ src/
ARG APP_VERSION
RUN sed -i "s/^.*\bAPP_VERSION\b.*$/pub const APP_VERSION: \&str = \"$APP_VERSION\";/g" src/meta.rs
ARG TARGETPLATFORM
RUN \
case $TARGETPLATFORM in \
"linux/386") RUST_TARGET="i686-unknown-linux-musl" ;; \
"linux/amd64") RUST_TARGET="x86_64-unknown-linux-musl" ;; \
"linux/arm/v6") RUST_TARGET="arm-unknown-linux-musleabi" ;; \
"linux/arm/v7") RUST_TARGET="armv7-unknown-linux-musleabi" ;; \
"linux/arm64") RUST_TARGET="aarch64-unknown-linux-musl" ;; \
*) false ;; \
esac \
&& rustup target add $RUST_TARGET \
&& cargo rustc --target=$RUST_TARGET --release -- -C linker=rust-lld -D warnings \
&& mv target/$RUST_TARGET/release/prometheus-nut-exporter .

## Runtime stage
FROM alpine:$ALPINE_VERSION AS runtime
WORKDIR /app

# Add non-root user
ARG APP_GID
ARG APP_UID
RUN addgroup -S -g $APP_GID app && adduser -S -G app -u $APP_UID app

# Add executable
COPY --from=builder /app/prometheus-nut-exporter ./
RUN chown app:app prometheus-nut-exporter

USER app
ENTRYPOINT ["./prometheus-nut-exporter"]