Best practices for reducing Docker image size for Node.js apps?

Hey there! 👋

Reducing the size of Docker images is always a good idea, especially when working with Node.js apps since smaller images help speed up your builds and deployments! Here are a few things that I usually do:

1. Instead of using the default node image, you can opt for node:alpine, which is a minimal version of the Node.js image based on Alpine Linux. It’s significantly smaller than the regular images:

   FROM node:alpine
   

2. Use multi-stage builds. This allows you to keep your final image clean and only include the necessary production dependencies. Here’s a basic example:

   # First stage: Build the app
   FROM node:alpine AS build
   WORKDIR /app
   COPY package*.json ./
   RUN npm install
   COPY . .
   RUN npm run build
   
   # Second stage: Production
   FROM node:alpine
   WORKDIR /app
   COPY --from=build /app .
   CMD ["node", "server.js"]
   

   With this, you only ship the final built app, excluding any development dependencies or unnecessary files which can help a lot!

3. Just like .gitignore, a .dockerignore file can prevent unnecessary files (like node_modules, logs, or .git) from being copied into your Docker image. Here’s an example .dockerignore:

   node_modules
   logs
   .git
   

4. Combine commands into a single RUN statement to reduce the number of layers in the final image:

   RUN apk add --no-cache bash && \
       npm install && \
       npm cache clean --force
   

5. When installing packages, make sure you clean up caches and unnecessary files. For example:

   RUN npm install && npm cache clean --force
   

6. When building for production, use the NODE_ENV environment variable to exclude dev dependencies:

   ENV NODE_ENV=production
   RUN npm install
   

Let me know if you need any more help!

- Bobby