Many teams, companies and companies had a struggle in containerizing their NodeJS web apps. There were many reasons behind it. There are multiple ways to dockerize a NodeJS and we will the some of the efficient ways that worked for me and are running successfully in production.
When we were trying to create a docker image for our Node JS based application, we chose to use the official Node docker image (~700MB). On top of that we need to add the node modules, business logic, etc and so on. The final image size was staggering (~1.2GB). It was not what we wanted. Secondly, the average build time to do NPM install and run a grunt task totally took 15 minutes for every build. I am not even talking about the pain of configuring this for different CI/CD pipelines and environments.
The initial docker file was looking something like this:
#Initial Docker File FROM node:6.10.1-alpine ENV APP_ENV $APP_ENV ENV BINPATH /usr/bin COPY wkhtmltox/bin/wkhtmltopdf /usr/local/bin/ RUN mkdir -p /usr/src/app WORKDIR /usr/src/app/
Install app dependencies
COPY package.json /usr/src/app/ #COPY start.sh /usr/src/app/ RUN npm install --production RUN npm install -g email@example.com
Bundle app source
COPY . /usr/src/app
Install pm2 so we can run our app
RUN npm i -g pm2
run grunt, cd to dist, node server.js
RUN grunt --env=prod
#COPY start.sh dist
ADD start.sh /start.sh
RUN chmod 755 /start.sh
- Docker Image Size
- Image build Time
- Configure the image building process for different environment pipeline
I first decided to upgrade to Node:6 because of the LTS (Long Term Support), next I wanted to use a slim version of official node docker image. I didn't choose the alpine version for the reason there is no official support for node-sass. There is plethora of docker images available with sass-alpine-node version. But I strongly recommend not to use it for security reasons.
Secondly, I want to build a base web image specific to my project with all the node modules dependencies installed. Whenever we add a new module to npm package, we need to build the base image once which is not going to happen super frequently.
The next thing, I did after updating to node 6 was to make use of in built node capabilities. You can read more about them in the official npmjs website more.
Removes the duplicate references of node modules
Removes the unreferenced node modules
Create a shrinkwrap to lock down the node module versions
This has reduced the number of modules get installed and the size of the node_modules directory. The final base image docker file looked like below.
ENV APP_ENV $APP_ENV
ENV BINPATH /usr/bin
COPY wkhtmltox/bin/wkhtmltopdf /usr/local/bin/
RUN mkdir -p /usr/src/app
COPY package.json /usr/src/app/
RUN npm install --production
Then I built a base image like below:
docker build -t base-web-image: .
After this I removed the executing the grunt task out the docker image build process and moved it to the build agent machine.
As a final step, whenever a business logic or new code is pushed a new image needs to be built as a final application. I referred the image built earlier and started to refer it in the second image
FROM base-web-image RUN mkdir -p /usr/src/app COPY dist /usr/src/app WORKDIR /usr/src/app CMD ["pm2 start"]
- Final image size: ~400MB (~1.2 GB earlier)
- Build time: 10 seconds (15 minutes earlier)
Note: All the image sizes mentioned are uncompressed version sizes. The actual size uploaded to docker registries will be compressed and will smaller than the sizes mentioned.
We will see an alternative approach with Docker multistage build in my next post.