Dockerfile.prod

ARG CRYSTAL_VERSION=1.5.0
FROM 84codes/crystal:${CRYSTAL_VERSION}-alpine as build

# Create a temporary folder to hold the files
WORKDIR /app

RUN apk upgrade --no-cache \
    && \
    apk add --update --no-cache \
          tzdata \
#         bash \
#         ca-certificates \
#         iputils \
#     && \
#     apk add --no-cache -X http://dl-cdn.alpinelinux.org/alpine/edge/testing watchexec \
    && \
    update-ca-certificates


# Create a non-privileged user
# defaults are appuser:10001
ARG IMAGE_UID="10001"
ENV UID=$IMAGE_UID
ENV USER=appuser

# See https://stackoverflow.com/a/55757473/12429735RUN
RUN adduser \
    --disabled-password \
    --gecos "" \
    --home "/nonexistent" \
    --shell "/sbin/nologin" \
    --no-create-home \
    --uid "${UID}" \
    "${USER}"

# Copy shard files and install shards
COPY shard.* .


RUN shards install --production --ignore-crystal-version --skip-postinstall --skip-executables


# Copy src last for better caching
COPY src src
COPY example example
RUN mkdir -p bin

# - Build the demo application
RUN crystal build --release --no-debug -o bin/eventbus example/application.cr 

SHELL ["/bin/ash", "-eo", "pipefail", "-c"]

# Extract binary dependencies
RUN for binary in /app/bin/*; do \
        ldd "$binary" | \
        tr -s '[:blank:]' '\n' | \
        grep '^/' | \
        xargs -I % sh -c 'mkdir -p $(dirname deps%); cp % deps%;'; \
    done

# Build a minimal docker image
FROM scratch
WORKDIR /
ENV PATH=$PATH:/

# Copy the user information over
COPY --from=build /etc/passwd /etc/passwd
COPY --from=build /etc/group /etc/group

# These are required for communicating with external services
COPY --from=build /etc/hosts /etc/hosts

# These provide certificate chain validation where communicating with external services over TLS
COPY --from=build /etc/ssl/certs/ca-certificates.crt /etc/ssl/certs/
ENV SSL_CERT_FILE=/etc/ssl/certs/ca-certificates.crt

# This is required for Timezone support
COPY --from=build /usr/share/zoneinfo/ /usr/share/zoneinfo/

# Copy the app into place
COPY --from=build /app/deps /
COPY --from=build /app/bin /

# Use an unprivileged user.
USER appuser:appuser

ENTRYPOINT ["/eventbus"]
CMD ["/eventbus"]