Dockerfile OK

gistfile1.txt

# STEP 1 - BUILD RELEASE 
# cannot use alpine 3.14.0 because of issue here with bcrypt-elxir compiling using make on docker:
# https://github.com/riverrun/bcrypt_elixir/issues/26#issuecomment-881966412
FROM hexpm/elixir:1.12.3-erlang-24.0.6-alpine-3.13.5 AS build

# install build dependencies
RUN apk add --update git \
    build-base \
    nodejs-current \
    nodejs-npm \
    yarn

RUN mkdir /app
WORKDIR /app

# install Hex + Rebar
RUN mix do local.hex --force, local.rebar --force

# set build ENV
ENV MIX_ENV=prod
ENV HOSTNAME=faithfulaudio.org
ENV DATABASE_URL=ecto://***:***@postgres/faithful_word
ENV SECRET_KEY_BASE=***

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

# build assets
COPY assets assets

RUN mix assets.deploy

# build project
COPY priv priv
COPY lib lib
RUN mix compile

# build release
# at this point we should copy the rel directory but
# we are not using it so we can omit it
# COPY rel rel
RUN mix release

####################################################################################################
# STEP 2 - FINAL
FROM alpine:3.13.5 as app
# install runtime dependencies
# https://stackoverflow.com/questions/68010688/docker-run-error-loading-shared-library-libstdc-so-6-and-libgcc-s-so-1
RUN apk upgrade --no-cache && \ 
    apk add --update bash \
    openssl \ 
    postgresql-client \
    libstdc++

EXPOSE 4000
ENV MIX_ENV=prod
ENV DATABASE_URL=ecto://***:***@postgres/faithful_word
ENV SECRET_KEY_BASE=***

# prepare app directory
RUN mkdir /app
WORKDIR /app

# copy release to app container
COPY --from=build /app/_build/prod/rel/faithful_word .
COPY entrypoint.sh .
RUN chown -R nobody: /app
USER nobody

ENV HOME=/app
CMD ["bash", "/app/entrypoint.sh"]