Dockerfile

# first, get the elixir dependencies within an elixir container
FROM hexpm/elixir:1.20.2-erlang-29.0.2-debian-bookworm-20260623-slim AS elixir-builder

ENV LANG="C.UTF-8" MIX_ENV="prod"

WORKDIR /root
ADD . .

# Install git so we can install dependencies from GitHub
RUN apt-get update && \
  apt-get install -y --no-install-recommends git ca-certificates

RUN mix do local.hex --force, local.rebar --force, deps.get --only prod

# next, build the frontend assets within a node.js container
FROM node:22.18.0 AS assets-builder

WORKDIR /root
ADD . .

# copy in elixir deps required to build node modules for phoenix
COPY --from=elixir-builder /root/deps ./deps

RUN npm ci --prefix assets && npm run deploy --prefix assets

# now, build the application back in the elixir container
FROM elixir-builder AS app-builder

WORKDIR /root

# add frontend assets compiled in node container, required by phx.digest
COPY --from=assets-builder /root/priv/static ./priv/static

RUN mix do compile --force, phx.digest, sentry.package_source_code, release

# the one the elixir image was built with
FROM hexpm/erlang:27.3.4-debian-bookworm-20250520-slim

WORKDIR /root
EXPOSE 4000
ENV MIX_ENV=prod TERM=xterm LANG="C.UTF-8" PORT=4000

# add frontend assets with manifests from app build container
COPY --from=app-builder /root/priv/static ./priv/static
COPY --from=app-builder /root/_build/prod/rel/signs_ui .
RUN mkdir gtfs

# Healthcheck
HEALTHCHECK CMD ["bin/signs_ui", "rpc", "1 + 1"]

# Start application
CMD ["bin/signs_ui", "start"]