Hex Cannot Be Found on Dockerized Phoenix App when running on Drone - docker

Question

So I currently have a setup wherein I deploy my dockerized Phoenix application to run tests on a self hosted Drone server. Currently the issue arises that no matter what Dockerfile I use(currently alpine-elixir-phoenix or a base elixir image with the following) which installs hex/rebar like below:
# Install Hex+Rebar
RUN mix local.hex --force && \
mix local.rebar --force
I receive the error upon booting in Drone,
Could not find Hex, which is needed to build dependency :phoenix
I have found that by using an older version of alpine-elixir-phoenix:2.0 this issue does not come up which leads me to believe it may be something to do with hex/elixir having updated since then? Additionally if I run the commands to install hex and rebar within the container in Drone once it is instantiated there is no issue. I ran a whoami on the instantiated Drone container and the user is root if that makes a difference. Additionally if I run the container locally and run mix hex.info, it correctly states that hex is installed, however the issue is that on the Drone instantiated container this fails.
Example .drone.yml:
pipeline:
backend_test:
image: bitwalker/alpine-elixir-phoenix
commands:
- cd api
- apk update
- apk add postgresql-client
- MIX_ENV=test mix local.hex --force
- MIX_ENV=test mix local.rebar --force
- MIX_ENV=test mix deps.get
- MIX_ENV=test mix ecto.create
- MIX_ENV=test mix ecto.migrate
- mix test
Example Docker File used(bitwalker/alpine-elixir-phoenix) - https://github.com/bitwalker/alpine-elixir-phoenix/blob/master/Dockerfile
where the same installation of local.hex and local.rebar occurs in the Dockerfile on lines 29 && 30. However upon instantiation of the container it is not found and therefore must be run again in the CMDs.
Furthermore I encountered this problem again but with make and g++ not installing on alpine. I may be doing something incorrect but I cannot see where.
testbuild_env Dockerfile
FROM bitwalker/alpine-erlang:19.2.1b
ENV HOME=/opt/app/ TERM=xterm
# Install Elixir and basic build dependencies
RUN \
echo "#edge http://nl.alpinelinux.org/alpine/edge/community" >> /etc/apk/repositories && \
apk update && \
apk --no-cache --update add \
git make g++ curl \
elixir#edge=1.4.2-r0 && \
rm -rf /var/cache/apk/*
# Install Hex+Rebar
RUN mix local.hex --force && \
mix local.rebar --force
ENV DOCKER_BUCKET test.docker.com
ENV DOCKER_VERSION 17.05.0-ce-rc1
ENV DOCKER_SHA256 4561742c2174c01ffd0679621b66d29f8a504240d79aa714f6c58348979d02c6
RUN set -x \
&& curl -fSL "https://${DOCKER_BUCKET}/builds/Linux/x86_64/docker-${DOCKER_VERSION}.tgz" -o docker.tgz \
&& echo "${DOCKER_SHA256} *docker.tgz" | sha256sum -c - \
&& tar -xzvf docker.tgz \
&& mv docker/* /usr/local/bin/ \
&& rmdir docker \
&& rm docker.tgz \
&& docker -v
COPY docker-entrypoint.sh /usr/local/bin/
ENTRYPOINT ["docker-entrypoint.sh"]
CMD ["sh"]
with the following .drone.yml
build:
image: test_buildenv
commands:
- cd api
- apk add make
- apk add g++
- MIX_ENV=test mix local.hex --force
- MIX_ENV=test mix local.rebar --force
- docker login --username USERNAME --password PASSWORD
- mix docker.build # creates a release file after running a dockerfile.build image
- mix docker.release # creates a minimalist image to run the release file that was just created
- mix docker.publish # pushes newly created image to dokcerh
volumes:
- /var/run/docker.sock:/var/run/docker.sock

Answer 1

The problem is that Drone builds its own isolated working environment as an extra layer on top of your docker image, so the ENV settings in your Dockerfile are not available. You need to independently tell Drone the environment info so it knows where hex is installed.
I managed to get this working by setting MIX_HOME in the .drone.yml file:
Dockerfile:
FROM bitwalker/alpine-elixir:1.8.1
RUN mix local.hex --force
.drone.yml:
pipeline:
build:
image: # built image of the above Dockerfile
environment:
MIX_HOME: /opt/app/.mix
commands:
- mix deps.get