I had a web application which is written in Node.js and I wanted to dockerize it. So went to the Node.js official site and found Dockerizing a Node.js web app article. I created the Dockerfile as it says in the article. Then I built the docker image with docker build, the created image size was 1.09GB
Dockerfile which produce 1.09GB docker image
FROM node:18
# Create app directory
WORKDIR /usr/src/app
# Install app dependencies
# A wildcard is used to ensure both package.json AND package-lock.json are copied
# where available (npm@5+)
COPY package*.json ./
RUN npm install
# If you are building your code for production
# RUN npm ci --omit=dev
# Bundle app source
COPY . .
EXPOSE 8080
CMD [ "node", "server.js" ]
Bigger images requires disk space and downloading them takes longer time. 1GB size was too big for me and i thought it could be reduced and investigated.
The image size can be reduced by the following steps:
1. Choose a Smaller Base Image
jessie, buster, stretch and alpine images are the smaller images. I’ve chosen the alpine image.
# Node.js alpine image as the base image
FROM node:18-alpine
2. Use Multi-Stage Docker Builds
Multi-stage builds are useful to anyone who has struggled to optimize Dockerfiles and then copy only the needed files to run the application into the final image.
The two stages are FROM node:18-alpine as builder and FROM node:18-alpine as final:
# Node.js alpine image as the base image. This is the build image stage
FROM node:18-alpine as builder
# Set the working directory in the container
WORKDIR /app
# Copy package.json and package-lock.json to the working directory
COPY package*.json ./
# Install app dependencies
RUN npm install
# Bundle app source
COPY . .
# The runtime image stage
FROM node:18-alpine as final
# Copy runtime files from builder image stage
COPY --from=builder /app/ /app/
# Set the working directory in the container
WORKDIR /app
# Expose the port your app runs on
EXPOSE 3000
# Define the command to run your app
CMD ["node", "server.js"]
3. Copy only the required files
Reduce the size of the image by making sure to only COPY the required files.
COPY --from=builder /app/node_modules /app/node_modules copies node_modules
COPY --from=builder /app/server.js /app/server.js copies server.js file which is the only required js file for my application to run.
# Node.js alpine image as the base image. This is the build image stage
FROM node:18-alpine as builder
# Set the working directory in the container
WORKDIR /app
# Copy package.json and package-lock.json to the working directory
COPY package*.json ./
# Install app dependencies
RUN npm install
# Bundle app source
COPY . .
# The runtime image stage
FROM node:18-alpine as final
# Copy only the required files from builder image stage
COPY --from=builder /app/node_modules /app/node_modules
COPY --from=builder /app/server.js /app/server.js
# Set the working directory in the container
WORKDIR /app
# Expose the port your app runs on
EXPOSE 3000
# Define the command to run your app
CMD ["node", "server.js"]
4. Install Production Dependencies Only or Omit devDependencies
ENV NODE_ENV=production causes to install only production on npm install.
RUN npm ci --omit=dev omits the dev dependencies.
# Node.js alpine image as the base image. This is the build image stage
FROM node:18-alpine as builder
# Bundle app source
COPY . /app
# Make node environment production
ENV NODE_ENV=production
WORKDIR /app
# Omit dev dependencies during npm install
RUN npm ci --omit=dev
# The runtime image stage
FROM node:18-alpine as final
# Copy only the required files from builder image stage
COPY --from=builder /app/node_modules /app/node_modules
COPY --from=builder /app/server.js /app/server.js
# Set the working directory in the container
WORKDIR /app
# Expose the port your app runs on
EXPOSE 3000
# Define the command to run your app
CMD ["node", "server.js"]
Result
After I applied all the steps, the final image size is reduced to 178MB.