Inspect Docker Image to Reduce Build Size
Frontend build
My Dockerfile for the frontend NextJS is very optimized for small build size outputting to the standalone feature
Frontend Dockerfile
ARG PRODUCTION_PLATFORM
FROM --platform=$PRODUCTION_PLATFORM node:20-alpine AS base
RUN echo '#### LETS GET STARTED HEYYY ####'
FROM base AS builder
# # Check https://github.com/nodejs/docker-node/tree/b4117f9333da4138b03a546ec926ef50a31506c3#nodealpine to understand why libc6-compat might be needed.
RUN apk add --no-cache libc6-compat
WORKDIR /app
# Install dependencies based on the preferred package manager
COPY package.json yarn.lock* package-lock.json* pnpm-lock.yaml* ./
# COPY keystone.ts schema.* session.ts envs.ts ./
# COPY src/keystone/schema.ts ./src/keystone/schema.ts
COPY . ./
RUN \
if [ -f yarn.lock ]; then yarn install --frozen-lockfile; \
elif [ -f package-lock.json ]; then npm ci; \
elif [ -f pnpm-lock.yaml ]; then corepack enable pnpm && pnpm i --frozen-lockfile; \
else echo "Lockfile not found." && exit 1; \
fi
RUN yarn add sharp
RUN yarn next telemetry disable
# Learn more here: https://nextjs.org/telemetry
ENV NEXT_TELEMETRY_DISABLED 1
RUN \
if [ -f yarn.lock ]; then yarn run build; \
elif [ -f package-lock.json ]; then npm run build; \
elif [ -f pnpm-lock.yaml ]; then corepack enable pnpm && pnpm run build; \
else echo "Lockfile not found." && exit 1; \
fi
RUN yarn next telemetry disable
# Production image, copy all the files and run next
FROM base AS runner
WORKDIR /app
ENV NEXT_TELEMETRY_DISABLED 1
ENV NODE_ENV production
# Uncomment the following line in case you want to disable telemetry during runtime.
RUN addgroup --system --gid 1001 nodejs
RUN adduser --system --uid 1001 nextjs
COPY --from=builder /app/public ./public
# COPY --from=builder /app/.keystone ./.keystone
# COPY --from=builder /app/schema.prisma ./schema.prisma
# Set the correct permission for prerender cache
RUN mkdir .next
RUN chown nextjs:nodejs .next
# Automatically leverage output traces to reduce image size
# https://nextjs.org/docs/advanced-features/output-file-tracing
COPY --from=builder --chown=nextjs:nodejs /app/.next/standalone ./
COPY --from=builder --chown=nextjs:nodejs /app/.next/static ./.next/static
USER nextjs
EXPOSE 3000
ENV PORT 3000
# server.js is created by next build from the standalone output
# https://nextjs.org/docs/pages/api-reference/next-config-js/output
CMD HOSTNAME="0.0.0.0" node server.js
Frontend end Docker Image inspected
## run this command to get below output
docker history myapp-frontend
IMAGE CREATED CREATED BY SIZE COMMENT
5c6aa2e91e8b 16 minutes ago CMD ["/bin/sh" "-c" "HOSTNAME=\"0.0.0.0\" no… 0B buildkit.dockerfile.v0
<missing> 16 minutes ago ENV PORT=3000 0B buildkit.dockerfile.v0
<missing> 16 minutes ago EXPOSE map[3000/tcp:{}] 0B buildkit.dockerfile.v0
<missing> 16 minutes ago USER nextjs 0B buildkit.dockerfile.v0
<missing> 16 minutes ago COPY --chown=nextjs:nodejs /app/.next/static… 2.57MB buildkit.dockerfile.v0
<missing> 16 minutes ago COPY --chown=nextjs:nodejs /app/.next/standa… 154MB buildkit.dockerfile.v0
<missing> 16 minutes ago RUN /bin/sh -c chown nextjs:nodejs .next # b… 0B buildkit.dockerfile.v0
<missing> 16 minutes ago RUN /bin/sh -c mkdir .next # buildkit 0B buildkit.dockerfile.v0
<missing> 16 minutes ago COPY /app/public ./public # buildkit 163kB buildkit.dockerfile.v0
<missing> 18 minutes ago RUN /bin/sh -c adduser --system --uid 1001 n… 3.25kB buildkit.dockerfile.v0
<missing> 18 minutes ago RUN /bin/sh -c addgroup --system --gid 1001 … 1.07kB buildkit.dockerfile.v0
<missing> 18 minutes ago ENV NODE_ENV=production 0B buildkit.dockerfile.v0
<missing> 18 minutes ago ENV NEXT_TELEMETRY_DISABLED=1 0B buildkit.dockerfile.v0
<missing> 18 minutes ago WORKDIR /app 0B buildkit.dockerfile.v0
<missing> 18 minutes ago RUN /bin/sh -c echo '#### LETS GET STARTED H… 0B buildkit.dockerfile.v0
<missing> 8 days ago CMD ["node"] 0B buildkit.dockerfile.v0
<missing> 8 days ago ENTRYPOINT ["docker-entrypoint.sh"] 0B buildkit.dockerfile.v0
<missing> 8 days ago COPY docker-entrypoint.sh /usr/local/bin/ # … 388B buildkit.dockerfile.v0
<missing> 8 days ago RUN /bin/sh -c apk add --no-cache --virtual … 5.59MB buildkit.dockerfile.v0
<missing> 8 days ago ENV YARN_VERSION=1.22.22 0B buildkit.dockerfile.v0
<missing> 8 days ago RUN /bin/sh -c addgroup -g 1000 node && … 118MB buildkit.dockerfile.v0
<missing> 8 days ago ENV NODE_VERSION=20.16.0 0B buildkit.dockerfile.v0
<missing> 10 days ago /bin/sh -c #(nop) CMD ["/bin/sh"] 0B
<missing> 10 days ago /bin/sh -c #(nop) ADD file:a71f7e9bc66668361… 8.83MB
Backend build
My backend build of a KeystoneJS app outputs to an eye watering 5gb image.
Backend Dockerfile
ARG PRODUCTION_PLATFORM
FROM --platform=$PRODUCTION_PLATFORM node:20-alpine as builder
WORKDIR /app
COPY package.json yarn.lock ./
COPY . .
RUN yarn install --production --frozen-lockfile
RUN yarn generate
RUN yarn ks:build
RUN yarn next telemetry disable
# Learn more here: https://nextjs.org/telemetry
ENV NEXT_TELEMETRY_DISABLED 1
FROM builder as runner
WORKDIR /app
COPY --from=builder /app/package.json .
# COPY --from=builder /app/yarn.lock .
# COPY --from=builder /app/.env .
COPY --from=builder /app/.keystone ./.keystone
# COPY --from=builder /app/schema.prisma ./schema.prisma
# COPY --from=builder /app/next.config.mjs ./
## todo try getting rid of `public` folder?
# COPY --from=builder /app/public ./public
## todo why is this image build to +5gb size?
# COPY --from=builder /app/node_modules ./node_modules
EXPOSE 3001
ENV NODE_ENV production
ENV PORT 3001
CMD ["yarn", "ks:start"]
Backend Docker Image inspected
docker history ksnext14-kypn-backend
IMAGE CREATED CREATED BY SIZE COMMENT
17c95e78a409 6 minutes ago CMD ["yarn" "ks:start"] 0B buildkit.dockerfile.v0
<missing> 6 minutes ago ENV PORT=3001 0B buildkit.dockerfile.v0
<missing> 6 minutes ago ENV NODE_ENV=production 0B buildkit.dockerfile.v0
<missing> 6 minutes ago EXPOSE map[3001/tcp:{}] 0B buildkit.dockerfile.v0
<missing> 6 minutes ago COPY /app/.keystone ./.keystone # buildkit 125MB buildkit.dockerfile.v0
<missing> 6 minutes ago COPY /app/package.json . # buildkit 1.4kB buildkit.dockerfile.v0
<missing> 6 minutes ago WORKDIR /app 0B buildkit.dockerfile.v0
<missing> 6 minutes ago ENV NEXT_TELEMETRY_DISABLED=1 0B buildkit.dockerfile.v0
<missing> 6 minutes ago RUN /bin/sh -c yarn next telemetry disable #… 2.2MB buildkit.dockerfile.v0
<missing> 6 minutes ago RUN /bin/sh -c yarn ks:build # buildkit 223MB buildkit.dockerfile.v0
<missing> 7 minutes ago RUN /bin/sh -c yarn generate # buildkit 17MB buildkit.dockerfile.v0
<missing> 7 minutes ago RUN /bin/sh -c yarn install --production --f… 4.18GB buildkit.dockerfile.v0
<missing> 24 minutes ago COPY . . # buildkit 1.15MB buildkit.dockerfile.v0
<missing> 24 minutes ago COPY package.json yarn.lock ./ # buildkit 414kB buildkit.dockerfile.v0
<missing> 38 minutes ago WORKDIR /app 0B buildkit.dockerfile.v0
<missing> 8 days ago CMD ["node"] 0B buildkit.dockerfile.v0
<missing> 8 days ago ENTRYPOINT ["docker-entrypoint.sh"] 0B buildkit.dockerfile.v0
<missing> 8 days ago COPY docker-entrypoint.sh /usr/local/bin/ # … 388B buildkit.dockerfile.v0
<missing> 8 days ago RUN /bin/sh -c apk add --no-cache --virtual … 5.59MB buildkit.dockerfile.v0
<missing> 8 days ago ENV YARN_VERSION=1.22.22 0B buildkit.dockerfile.v0
<missing> 8 days ago RUN /bin/sh -c addgroup -g 1000 node && … 118MB buildkit.dockerfile.v0
<missing> 8 days ago ENV NODE_VERSION=20.16.0 0B buildkit.dockerfile.v0
<missing> 10 days ago /bin/sh -c #(nop) CMD ["/bin/sh"] 0B
<missing> 10 days ago /bin/sh -c #(nop) ADD file:a71f7e9bc66668361… 8.83MB
The Problem
From the RUN /bin/sh -c yarn install --production --f… 4.18GB buildkit.dockerfile.v0 line I can see that most of that bloat comes from the yarn install command
But why would the frontend at a tiny size?
inspecting a running backend container
With a bit of prodding, I find that the yarn cache is gigantic
cd /app
du -sh /usr/local/share/.cache/yarn/v6/
3.2G
WOH, even with my node_modules installed, the local dev directory does not even reach that size.
I'm dumb
I overlooked the line FROM builder AS runner. It should have been FROM base AS runner as to not copy over any files from the build step