How to cache the RUN npm install instruction when docker build a Dockerfile
I imagine you may already know, but you could include a .dockerignore file in the same folder containing
node_modules
npm-debug.log
to avoid bloating your image when you push to docker hub
I've found that the simplest approach is to leverage Docker's copy semantics:
The COPY instruction copies new files or directories from and adds them to the filesystem of the container at the path .
This means that if you first explicitly copy the package.json file and then run the npm install step that it can be cached and then you can copy the rest of the source directory. If the package.json file has changed, then that will be new and it will re-run the npm install caching that for future builds.
A snippet from the end of a Dockerfile would look like:
# install node modules
WORKDIR /usr/app
COPY package.json /usr/app/package.json
RUN npm install
# install application
COPY . /usr/app
Ok so I found this great article about efficiency when writing a docker file.
This is an example of a bad docker file adding the application code before running the RUN npm install instruction:
FROM ubuntu
RUN echo "deb http://archive.ubuntu.com/ubuntu precise main universe" > /etc/apt/sources.list
RUN apt-get update
RUN apt-get -y install python-software-properties git build-essential
RUN add-apt-repository -y ppa:chris-lea/node.js
RUN apt-get update
RUN apt-get -y install nodejs
WORKDIR /opt/app
COPY . /opt/app
RUN npm install
EXPOSE 3001
CMD ["node", "server.js"]
By dividing the copy of the application into 2 COPY instructions (one for the package.json file and the other for the rest of the files) and running the npm install instruction before adding the actual code, any code change wont trigger the RUN npm install instruction, only changes of the package.json will trigger it. Better practice docker file:
FROM ubuntu
MAINTAINER David Weinstein <[email protected]>
# install our dependencies and nodejs
RUN echo "deb http://archive.ubuntu.com/ubuntu precise main universe" > /etc/apt/sources.list
RUN apt-get update
RUN apt-get -y install python-software-properties git build-essential
RUN add-apt-repository -y ppa:chris-lea/node.js
RUN apt-get update
RUN apt-get -y install nodejs
# use changes to package.json to force Docker not to use the cache
# when we change our application's nodejs dependencies:
COPY package.json /tmp/package.json
RUN cd /tmp && npm install
RUN mkdir -p /opt/app && cp -a /tmp/node_modules /opt/app/
# From here we load our application's code in, therefore the previous docker
# "layer" thats been cached will be used if possible
WORKDIR /opt/app
COPY . /opt/app
EXPOSE 3000
CMD ["node", "server.js"]
This is where the package.json file added, install its dependencies and copy them into the container WORKDIR, where the app lives:
ADD package.json /tmp/package.json
RUN cd /tmp && npm install
RUN mkdir -p /opt/app && cp -a /tmp/node_modules /opt/app/
To avoid the npm install phase on every docker build just copy those lines and change the ^/opt/app^ to the location your app lives inside the container.
Weird! No one mentions multi-stage build.
# ---- Base Node ----
FROM alpine:3.5 AS base
# install node
RUN apk add --no-cache nodejs-current tini
# set working directory
WORKDIR /root/chat
# Set tini as entrypoint
ENTRYPOINT ["/sbin/tini", "--"]
# copy project file
COPY package.json .
#
# ---- Dependencies ----
FROM base AS dependencies
# install node packages
RUN npm set progress=false && npm config set depth 0
RUN npm install --only=production
# copy production node_modules aside
RUN cp -R node_modules prod_node_modules
# install ALL node_modules, including 'devDependencies'
RUN npm install
#
# ---- Test ----
# run linters, setup and tests
FROM dependencies AS test
COPY . .
RUN npm run lint && npm run setup && npm run test
#
# ---- Release ----
FROM base AS release
# copy production node_modules
COPY --from=dependencies /root/chat/prod_node_modules ./node_modules
# copy app sources
COPY . .
# expose port and define CMD
EXPOSE 5000
CMD npm run start
Awesome tuto here: https://codefresh.io/docker-tutorial/node_docker_multistage/