Qfyilyi

For node applications, what is the better option for building lightweight images?

1. 
   

   Single Docker Image. Might require build tools and would expose all build time environment variables to the container.

   
   
   

   yarn install # install deps and devDeps
   
   yarn build # build our application
   
   yarn test # perform tests
   
   yarn install --production --ignore-scripts --prefer-offline # Remove devDeps
   
   rm -rf src # Remove source files
   
   yarn start
   
   

   
   


2. 
   

   Multiple Docker Images

   
   
   

   In one docker container that has build tools, do the:

   
   
   

   yarn install
   
   yarn build
   
   yarn test
   
   

   
   
   

   Then take the build assets and package.json, and copy them into a new container which would have only runtime environment variables. The result is a much smaller image (perhaps node:alpine) that has only very limited source files.

   
   
   

   yarn install --production --ignore-scripts --prefer-offline
   
   yarn start
   
   

   
   

If you want to build lightweight image for your application, keep in mind the following:

1. Try to use alpine images, e.g. node:8.12.0-alpine as alpine images are lightest base os image. If you want to install packages, do RUN apk add --no-cache --virtual your_packages... && rm -rf /var/cache/apk/*




2. Try to reduce number of layers by running multiple commands in same RUN statement, e.g. RUN yarn install && yarn build && yarn test && yarn install --production --ignore-scripts --prefer-offline && rm
-rf src && yarn start




3. Try to club commands that cancel out each other, e.g. RUN apk update && apk add ... && rm -rf /var/cache/apk/*. Here apk update creates a cache and rm -rf /var/cache/apk/* clears it. No need to run these two commands separately as they are cancelling out each others work hence no point in having two layers which negate each other and inflate the size of the final image.

Note: Having multiple docker files instead of one is not going to reduce the number of layers or shrink the size. It only gives you logical separation of tasks that you want to handle individually.