Install node modules before copying over your working code so that node_modules are built (and cached) before you change your service code!

Dockerfile-nodejs

# ...
ADD package.json /tmp/package.json
RUN cd /tmp && npm install && \
    mkdir -p /opt/app && cp -a /tmp/node_modules /opt/app/

# ...
WORKDIR /opt/app
ADD . /opt/app

If the package.json file changes then Docker will re-run the npm install sequence... otherwise our modules are cached so we aren't rebuilding them every time we change our apps source code!

If the package.json file changes then Docker will re-run the npm install sequence... otherwise our modules are cached so we aren't rebuilding them every time we change our apps source code!

👍

👍

For those like myself who were initially bewildered by this, the "Build cache" section of the Dockerfile best practices doc may help fill in the gaps.

For those like myself who were initially bewildered by this, the "Build cache" section of the Dockerfile best practices doc may help fill in the gaps.