Deployment Files

The Docker-Compose File (run)

The following file docker-compose.yml is used to run a docker-container with an image created in Dockerfile.

The dockerfile builds the phoenix-release of iBoard blog.

The docker-compose file packs a stack with two services.

• web (The Phoenix application)
• db (A Postgres database)

docker-compose.yml

services:
  db:
    image: postgres:16-alpine
    environment:
      POSTGRES_USER: ${PGUSER:-blog}
      POSTGRES_PASSWORD: ${PGPASSWORD:?Set PGPASSWORD in .env}
      POSTGRES_DB: ${PGDATABASE:-blog_prod}
    volumes:
      - ./data/postgres:/var/lib/postgresql/data
    expose:
      - "5432"
    networks:
      - backend
    restart: unless-stopped
    healthcheck:
      test: ["CMD-SHELL", "pg_isready -U ${PGUSER:-blog}"]
      interval: 10s
      timeout: 5s
      retries: 5

  web:
    image: iboard/blog:latest
    env_file:
      - path: ./.env
        required: false
    environment:
      PHX_SERVER: "true"
      # Endpoint
      ENDPOINT_HOST: ${ENDPOINT_HOST:?Set ENDPOINT_HOST in .env}
      ENDPOINT_SCHEME: ${ENDPOINT_SCHEME:-https}
      ENDPOINT_PORT: ${ENDPOINT_PORT:-4000}
      ENDPOINT_IP: ${ENDPOINT_IP:-0.0.0.0}
      # Database — connects to the db service on the internal network
      DATABASE_URL: "ecto://${PGUSER:-blog}:${PGPASSWORD}@db/${PGDATABASE:-blog_prod}"
      POOL_SIZE: ${POOL_SIZE:-10}
      # Security
      SECRET_KEY_BASE: ${SECRET_KEY_BASE:?Set SECRET_KEY_BASE in .env}
      # Mailer
      MAILER_ADAPTER: ${MAILER_ADAPTER:-sendgrid}
      SENDGRID_API_KEY: ${SENDGRID_API_KEY:-}
      # Logging
      LOG_LEVEL: ${LOG_LEVEL:-info}
      # Clustering (optional)
      DNS_CLUSTER_QUERY: ${DNS_CLUSTER_QUERY:-}
    ports:
      # Host port EXPOSE_PORT → container port ENDPOINT_PORT.
      # Put an nginx reverse proxy in front to terminate TLS on 443.
      - "${EXPOSE_PORT:-4000}:${ENDPOINT_PORT:-4000}"
    volumes:
      - ./data/uploads:/app/uploads
    depends_on:
      db:
        condition: service_healthy
    networks:
      - backend
    restart: unless-stopped

networks:
  backend:
    driver: bridge

Dockerfile

The following dockerfile builds an image from a slim Debian, packed with Erlang and Elixir.

It uses mix to build a release and a docker image.

# Builder Stage
FROM hexpm/elixir:1.19.5-erlang-28.4-debian-bookworm-20260223-slim AS builder

ENV MIX_ENV=prod

WORKDIR /build

# Install build dependencies
RUN apt-get update -y && apt-get install -y build-essential git \
    && apt-get clean && rm -f /var/lib/apt/lists/*_*

# Install hex and rebar
RUN mix local.hex --force && mix local.rebar --force

# Install mix dependencies
COPY mix.exs mix.lock ./
COPY config config
COPY README.md README.md
COPY CHANGELOG.md CHANGELOG.md
COPY TODO.md TODO.md
RUN mix deps.get --only $MIX_ENV
RUN mix deps.compile

# Copy application code
COPY priv priv
COPY lib lib
COPY assets assets
# run mix doesn't compile - FIXME: find another way to deploy docs
# RUN mix docs
COPY doc priv/static/docs

# Deploy assets
# Provide dummy environment variables for config/runtime.exs evaluation during build
ENV DATABASE_URL=ecto://postgres:postgres@localhost/w_app_core_prod
#ENV SECRET_KEY_BASE=dummy_secret_key_base_for_build_only_must_be_at_least_64_bytes_long_so_we_add_some_more_chars_here

# Compile the release
RUN mix compile
RUN mix assets.deploy
RUN mix release

# Runner Stage
FROM debian:bookworm-slim AS runner

ENV MIX_ENV=prod

# Install runtime dependencies including wkhtmltopdf
# wkhtmltopdf fontconfig libjpeg62-turbo libxrender1 xfonts-75dpi xfonts-base \
# pdftk \
RUN apt-get update -y && \
    apt-get install -y libstdc++6 openssl libncurses5 locales \
    && apt-get clean && rm -f /var/lib/apt/lists/*_*

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

ENV LANG=en_US.UTF-8
ENV LANGUAGE=en_US:en
ENV LC_ALL=en_US.UTF-8

WORKDIR /app

# Copy the built release from the builder stage
COPY --from=builder /build/_build/prod/rel/w_app_core ./
COPY doc priv/static/docs

# Expose default port
EXPOSE 4000

CMD ["sh", "-c", "/app/bin/w_app_core eval WAppCore.Release.migrate && /app/bin/w_app_core start"]