Why is docker image is too big? NodeJS app

user_13555674 0
Viewed 2546

I am building my app into docker image.

My docker file:

FROM node:12-alpine

WORKDIR /usr/app

COPY ./package.json ./package.json

RUN yarn

COPY ./src ./src
COPY ./gulpfile.js ./gulpfile.js
COPY ./tsconfig.json ./tsconfig.json

RUN yarn build

RUN rm -rf ./node_modules
RUN rm -rf ./src
RUN rm -rf ./gulpfile.js
RUN rm -rf ./yarn.lock
RUN rm -rf ./package.json
RUN rm ./tsconfig.json

RUN cd dist && yarn 

CMD ["node", "./dist/boot.js"]

After build I opened docker image and found my app in /user/app/dist size is 264MB (including node_modules).

But docker image has 867MB.

Why?

is there anything wrong in my dockerfile script? I am using node alpine, it should be small.

docker node.js
1 Answers

Adding lines to a Dockerfile never makes an image smaller. Because of the way an image is constructed from layers, a RUN line generally results in everything from the previous layer, plus whatever changes result from that RUN command.

As a specific example in your Dockerfile:

# Build the contents of the dist/ directory
RUN yarn build

# Keep the entire contents of the previous layer
# PLUS add markers that the node_modules directory should be removed
RUN rm -rf ./node_modules

As @jonrsharpe points out in comments, you're probably looking for a multi-stage build. The basic concept here is that a second FROM line will cause docker build to completely start over from a new base image, but then you can COPY --from= a previous stage into the final stage.

You might rebuild your existing image like so:

# Add "AS build" for later use
FROM node:12-alpine AS build

# This is exactly what you had before
WORKDIR /usr/app
COPY ./package.json ./package.json
RUN yarn
COPY ./src ./src
COPY ./gulpfile.js ./gulpfile.js
COPY ./tsconfig.json ./tsconfig.json
RUN yarn build

# Now build the actual image, starting over.
FROM node:12-alpine
WORKDIR /usr/app
COPY --from=build /usr/src/app/dist .
# but not its node_modules tree or anything else
CMD ["node", "boot.js"]
user_100081730
Related