NextJS - Docker Multistage

This post will focus on the way to dockerize a NextJS application. Here, we will see how to use multi-stage docker to optimize the final docker image.

Setup

The first step is to create a Dockerfile file into your project directory. The goal here is to build and create a multi-stage image to being able to build an optimized Docker image. Each stage will be built in separate layer so each layer will be lightweight.

FROM node:lts-alpine as dependencies
WORKDIR /app
COPY package.json yarn.lock ./
RUN yarn install --frozen-lockfile

FROM node:lts-alpine as builder
WORKDIR /app
COPY . .
COPY --from=dependencies /app/node_modules ./node_modules
RUN yarn build

FROM node:lts-alpine as runner

ARG APP=/app

ENV APP_USER=runner
RUN addgroup -S $APP_USER \
    && adduser -S $APP_USER -G $APP_USER \
    && mkdir -p ${APP}

RUN chown -R $APP_USER:$APP_USER ${APP}

WORKDIR /app

COPY --from=builder /app/next.config.js ./
COPY --from=builder /app/public ./public
COPY --from=builder /app/.next ./.next
COPY --from=builder /app/node_modules ./node_modules
COPY --from=builder /app/package.json ./package.json

We are setting a custom user runner for security.

Ignore unwanted files

The .dockerignore file will act as .gitignore, It uses a different pattern, each match will be excluded from the docker image when building It.

# add git-ignore syntax here of things you don't want copied into docker image

.git
*Dockerfile*
node_modules
.env

Compose

The docker-compose.yaml will then be used for development purpose as we may rely on Kubernetes for deployment.

You will need to adapt image: value.

services:
  app:
    image: ghcr.io/my-github-username/my-blog-name
    build:
      context: .
      dockerfile: Dockerfile
    ports:
      - 3000:3000
    command: ["yarn", "dev"]
    environment:
      - "NODE_ENV=development"
    stdin_open: true
    tty: true
    volumes:
      - .:/app
      - /app/node_modules
      - /app/.next

Using It

Now you can just launch your application in development mode by running docker-compose up

Production

• You will need to adapt NODE_ENV environment variable to production
• The command for running the container will be ["yarn", "start"]