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Cache npm install on docker

Docker had a great cache mechanism, and you can easily use it to improve your image build time.

Node Application Dockerfile

You can use the below Dockerfile to run a simple nodejs application, but for every image build the command npm install will be executed.

FROM node
ADD . /code
WORKDIR /code
RUN npm install
CMD npm start

Use docker layer cache

A great optimization to the previous Dockerfile is to run npm install before adding your codebase. For this you will have to add package.json and to run nmp install, before you add your codebase.

FROM node
ADD ./package.json /code/package.json
WORKDIR /code
RUN npm install
ADD . /code
CMD npm start

Conclusion

Now your npm install are cached and will be rerunned only if your package.json changes, making your image build time faster.