Dockerfile

ARG MIX_ENV="prod"

FROM hexpm/elixir:1.12.1-erlang-24.0.5-alpine-3.14.0 AS build

# install build dependencies
RUN apk add --no-cache build-base curl git

# prepare build dir
WORKDIR /app

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

# set build ENV
ARG MIX_ENV
ENV MIX_ENV="${MIX_ENV}"

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

# Dependencies sometimes use compile-time configuration. Copying
# these compile-time config files before we compile dependencies
# ensures that any relevant config changes will trigger the dependencies
# to be re-compiled.
COPY config/config.exs config/$MIX_ENV.exs ./config/
RUN mix deps.compile

# Note: if your project uses a tool like https://purgecss.com/,
# which customizes asset compilation based on what it finds in
# your Elixir templates, you will need to move the asset compilation
# step down so that `lib` is available.
COPY assets assets
RUN mix assets.deploy

# compile and build the release
COPY lib lib
RUN mix compile
# changes to config/runtime.exs don't require recompiling the code
COPY config/runtime.exs config/
# uncomment COPY if rel/ exists
# 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 alpine:3.14.0 AS app
RUN apk add --no-cache libstdc++ openssl ncurses-libs

ARG MIX_ENV
ENV USER="elixir"

WORKDIR "/home/${USER}/app"
# Creates an unprivileged user to be used exclusively to run the Phoenix app
RUN \
  addgroup \
  -g 1000 \
  -S "${USER}" \
  && adduser \
  -s /bin/sh \
  -u 1000 \
  -G "${USER}" \
  -h /home/elixir \
  -D "${USER}" \
  && su "${USER}"

# Everything from this line onwards will run in the context of the unprivileged user.
USER "${USER}"

COPY --from=build --chown="${USER}":"${USER}" /app/_build/"${MIX_ENV}"/rel/drops ./

ENTRYPOINT ["bin/drops"]

# Usage:
#  * build: sudo docker image build -t drops/app .
#  * shell: sudo docker container run --rm -it --entrypoint "" -p 127.0.0.1:4000:4000 drops/app sh
#  * run:   sudo docker container run --rm -it -p 127.0.0.1:4000:4000 --name drops drops/app
#  * exec:  sudo docker container exec -it drops sh
#  * logs:  sudo docker container logs --follow --tail 100 drops
CMD ["start"]