Dockerfile

# Find eligible builder and runner images on Docker Hub. We use Ubuntu/Debian
# instead of Alpine to avoid DNS resolution issues in production.
#
#   - https://hub.docker.com/r/hexpm/elixir/tags
#   - https://hub.docker.com/_/debian?tab=tags&page=1&name=bookworm
#
# NOTE: OTP must be >= 27.3.3. Earlier 27.x releases (incl. 27.2) reject the
# Let's Encrypt / ISRG "Root YR" cross-signed chain now served by hex.pm with a
# TLS "key_usage_mismatch" error, breaking `mix local.hex` / `mix deps.get`.
ARG ELIXIR_VERSION=1.17.3
ARG OTP_VERSION=27.3.4.11
ARG DEBIAN_VERSION=bookworm-20260610-slim

ARG BUILDER_IMAGE="hexpm/elixir:${ELIXIR_VERSION}-erlang-${OTP_VERSION}-debian-${DEBIAN_VERSION}"
ARG RUNNER_IMAGE="debian:${DEBIAN_VERSION}"

FROM ${BUILDER_IMAGE} as builder

# install build dependencies
RUN apt-get update -y && apt-get install -y build-essential git \
    && apt-get clean && rm -f /var/lib/apt/lists/*_*

# prepare build dir
WORKDIR /app

# install hex + rebar
RUN mix local.hex --force && \
    mix local.rebar --force

# set build ENV
ENV MIX_ENV="prod"

# install mix dependencies
COPY mix.exs mix.lock ./
RUN mix deps.get --only $MIX_ENV
RUN mkdir config

# copy compile-time config files before we compile dependencies
# to ensure any relevant config change will trigger the dependencies
# to be re-compiled.
COPY config/config.exs config/${MIX_ENV}.exs config/
RUN mix deps.compile

COPY priv priv
COPY lib lib
COPY assets assets

# Tailwind + esbuild are managed via mix; no npm step needed.
RUN mix assets.deploy

# Compile the release
RUN mix compile

# Changes to config/runtime.exs don't require recompiling the code
COPY config/runtime.exs config/

COPY rel rel
RUN mix release

# start a new build stage so that the final image will only contain
# the compiled release and other runtime necessities
FROM ${RUNNER_IMAGE}

RUN apt-get update -y && \
  apt-get install -y libstdc++6 openssl libncurses6 locales ca-certificates tini \
  && apt-get clean && rm -f /var/lib/apt/lists/*_*

# Set the locale
RUN sed -i '/en_US.UTF-8/s/^# //g' /etc/locale.gen && locale-gen

ENV LANG=en_US.UTF-8 \
    LANGUAGE=en_US:en \
    LC_ALL=en_US.UTF-8

WORKDIR "/app"
RUN chown nobody /app

# set runner ENV
ENV MIX_ENV="prod"

# Only copy the final release from the build stage
COPY --from=builder --chown=nobody:root /app/_build/${MIX_ENV}/rel/diogramos ./

USER nobody

# tini reaps zombies + forwards signals so PostgreSQL connections get
# closed cleanly on SIGTERM.
ENTRYPOINT ["/usr/bin/tini", "--"]
CMD ["/app/bin/server"]