Dockerized multi-stage NextJs build in standalone mode, to be served by nginx-proxy

Dockerfile

/**
 * This was pieced together from multiple sources on the web,
 * but none of them had solved directory structure for standalone mode at the time.
 *
 * The final structure used here allows the following location block in nginx:
 * 
 * proxy_pass http://localhost:3000/
 */

# Dockerfile
ARG BUILD_NODE=node:19
ARG RUN_NODE=node:19-alpine

# Stage 1: Install dependencies
FROM $BUILD_NODE AS deps
WORKDIR /app

COPY ["package.json", "yarn.lock", "./"]
RUN yarn --frozen-lockfile --non-interactive

# Stage 2: Build the app
FROM $BUILD_NODE AS builder
WORKDIR /app
COPY --from=deps /app/node_modules node_modules/
COPY . .
RUN yarn build

# Stage 3: Run the app in production mode
FROM $RUN_NODE AS runner
WORKDIR /app

ENV NODE_ENV=production
ENV NEXT_TELEMETRY_DISABLED 1

RUN addgroup --system --gid 1001 nodejs
RUN adduser --system --uid 1001 nextjs

# @TODO copy these to named volume to be served by nginx
# copy assets and the generated standalone server
COPY --from=builder --chown=nextjs:nodejs app/next.config.mjs app/.next/standalone/ ./
COPY --from=builder --chown=nextjs:nodejs app/.next/standalone/.next/* .next/
COPY --from=builder --chown=nextjs:nodejs app/public/ public/
COPY --from=builder --chown=nextjs:nodejs app/.next/static/ .next/static/

USER nextjs

EXPOSE 3000

ENV PORT 3000

# Serve the app
CMD ["node", "./server.js"]