docker-compose.yml

version: '3.5'

services:
  web:
    image: "integra_umbrella:latest"
    ports:
      - "4000:4000" # In our .env file above, we chose port 4000
    env_file:
      - config/docker.env
    depends_on:
      - db
  db:
    image: postgres:10-alpine
    volumes:
      - "./volumes/postgres:/var/lib/postgresql/data"
    ports:
      - "5432:5432"
    env_file:
      - config/docker.env

Dockerfile

# The version of Alpine to use for the final image
# This should match the version of Alpine that the `elixir:1.7.2-alpine` image uses
ARG ALPINE_VERSION=3.8

FROM elixir:1.7.2-alpine AS builder

# The following are build arguments used to change variable parts of the image.
# The name of your application/release (required)
ARG APP_NAME
# The version of the application we are building (required)
ARG APP_VSN
# The environment to build with
ARG MIX_ENV=prod
# Set this to true if this release is not a Phoenix app
ARG SKIP_PHOENIX=true
# If you are using an umbrella project, you can change this
# argument to the directory the Phoenix app is in so that the assets
# can be built
ARG PHOENIX_SUBDIR=.

ENV SKIP_PHOENIX=${SKIP_PHOENIX} \
    APP_NAME=${APP_NAME} \
    APP_VSN=${APP_VSN} \
    MIX_ENV=${MIX_ENV}

# By convention, /opt is typically used for applications
WORKDIR /opt/app

# This step installs all the build tools we'll need
RUN apk update && \
  apk upgrade --no-cache && \
  apk add --no-cache \
    nodejs \
    yarn \
    git \
    build-base && \
  mix local.rebar --force && \
  mix local.hex --force

# This copies our app source code into the build container
COPY . .

RUN mix do deps.get, deps.compile, compile

# This step builds assets for the Phoenix app (if there is one)
# If you aren't building a Phoenix app, pass `--build-arg SKIP_PHOENIX=true`
# This is mostly here for demonstration purposes
RUN if [ ! "$SKIP_PHOENIX" = "true" ]; then \
  cd ${PHOENIX_SUBDIR}/assets && \
  yarn install && \
  yarn deploy && \
  cd .. && \
  mix phx.digest; \
fi

RUN \
  mkdir -p /opt/built && \
  mix release --verbose && \
  cp _build/${MIX_ENV}/rel/${APP_NAME}/releases/${APP_VSN}/${APP_NAME}.tar.gz /opt/built && \
  cd /opt/built && \
  tar -xzf ${APP_NAME}.tar.gz && \
  rm ${APP_NAME}.tar.gz

# From this line onwards, we're in a new image, which will be the image used in production
FROM alpine:${ALPINE_VERSION}

# The name of your application/release (required)
ARG APP_NAME

RUN apk update && \
    apk add --no-cache \
      bash \
      openssl-dev

ENV REPLACE_OS_VARS=true \
    APP_NAME=${APP_NAME}

WORKDIR /opt/app

COPY --from=builder /opt/built .

CMD /opt/app/bin/${APP_NAME} foreground