Elixir phoenix docker setup

.iex.exs

:logger.debug("""

  > `docker attach $(docker compose ps web -q)` to attach IEx.pry()
  > Ctrl + P + Q to detach from the container terminal
""")

dev.exs

# default stuff

config :chatter, ChatterWeb.Endpoint,
  # Binding to loopback ipv4 address prevents access from other machines.
  # Change to `ip: {0, 0, 0, 0}` to allow access from other machines.
  http: [ip: {0, 0, 0, 0}, port: 4000],
  
# default stuff

docker-compose.yml

services:
  web:
    image: chit_chat-dev:1.0.1
    build:
      context: .
      dockerfile: Dockerfile
      target: builder
      args:
        MIX_ENV: ${MIX_ENV:-dev}
    environment:
      DATABASE_URL: postgres://postgres:postgres@db:5432/chit_chat_dev
      SECRET_KEY_BASE: cQ3VLNX5nkxRgQC4idmVfHYnzf51KkFFp4ACZuIBT61in2cWWbWpkEYDx2RQiPFz
    ports:
      - '4000:4000'
    depends_on:
      - db
    volumes:
      - .:/app:cached
    command: iex -S mix phx.server
    stdin_open: true
    tty: true

  db:
    image: postgres:17-alpine
    environment:
      POSTGRES_PASSWORD: postgres
      POSTGRES_USER: postgres
      POSTGRES_DB: chit_chat_dev
    ports:
      - 5432
    volumes:
      - pgdata:/var/lib/postgresql/data
    healthcheck:
      test: pg_isready -U postgres -h 127.0.0.1
      interval: 5s

volumes:
   pgdata:

Dockerfile

ARG DEBIAN_VERSION=bookworm-20250203-slim
ARG BUILDER_IMAGE="hexpm/elixir:1.18.2-erlang-27.2.4-debian-${DEBIAN_VERSION}"
ARG RUNNER_IMAGE="debian:${DEBIAN_VERSION}"

FROM $BUILDER_IMAGE as builder

# Build Args
ARG PHOENIX_VERSION=1.7.20
ARG MIX_ENV
ENV MIX_ENV=${MIX_ENV:-prod}
ARG DEBIAN_FRONTEND="noninteractive"
# ARG NODEJS_VERSION=16.x

# Apt
RUN apt-get update -qq \
    && apt-get -yq dist-upgrade \
    && apt-get install -yq --no-install-recommends \
       apt-utils \
       build-essential \
       git \
       postgresql-client-15 \
       inotify-tools \
    && apt-get clean \
    && rm -rf /var/cache/apt/archives/* \
    && rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/* \
    && truncate -s 0 /var/log/*log

# Nodejs
# RUN curl -sL https://deb.nodesource.com/setup_${NODEJS_VERSION} | bash
# RUN apt-get install -y nodejs

RUN mix local.hex --force && \
    mix archive.install --force hex phx_new $PHOENIX_VERSION && \
    mix local.rebar --force

# App Directory
WORKDIR /app

COPY mix.* ./
RUN mix deps.get --only $MIX_ENV

RUN mkdir config
COPY config/config.exs config/$MIX_ENV.exs config/

RUN mix deps.compile

COPY . ./

RUN if [ "${MIX_ENV}" = "prod" ]; then \
  mix compile && \
  MIX_ENV=prod mix assets.deploy && \
  mix release ; fi

COPY entrypoint.sh /usr/bin/
ENTRYPOINT ["entrypoint.sh"]

CMD ["mix phx.server"]

FROM $RUNNER_IMAGE as app
ARG DEBIAN_FRONTEND="noninteractive"
ENV LANG=en_US.UTF-8 \
    LANGUAGE=en_US:en \
    LC_ALL=en_US.UTF-8 \
    MIX_ENV=prod

RUN apt-get update -qq  \
    && apt-get install -yq --no-install-recommends \
    libstdc++6 openssl libncurses5 locales \
    && apt-get clean \
    && rm -rf /var/cache/apt/archives/* \
    && rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/* \
    && truncate -s 0 /var/log/*log

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

WORKDIR /app

COPY --from=builder /app/_build/prod/rel/chit_chat ./
COPY --from=builder /app/rel ./rel

CMD ["/app/bin/server"]

entrypoint.sh

#!/bin/bash
set -e

exec "$@"

runtime.exs

# default stuff

database_url =
  System.get_env("DATABASE_URL") ||
    raise """
    environment variable DATABASE_URL is missing.
    For example: ecto://USER:PASS@HOST/DATABASE
    """
maybe_ipv6 = if System.get_env("ECTO_IPV6") in ~w(true 1), do: [:inet6], else: []

config :mocha, Mocha.Repo,
  # ssl: true,
  url: database_url,
  pool_size: String.to_integer(System.get_env("POOL_SIZE") || "10"),
  socket_options: maybe_ipv6

if config_env() == :prod do
  # default stuff
end

test.exs

# default stuff

config :pay, Chatter.Repo,
  pool: Ecto.Adapters.SQL.Sandbox,
  pool_size: 10

# default stuff