Docker has emerged to be a standard of building and deploying applications. The best part of docker is it gives a complete abstraction over the environment or OS. There are plenty of material on what docker is, or how it works, however, what we are going to discuss over here is to how to put your nodeJS express app in docker container.
First things first
What we need
- A computer with docker installed on it. Preferably linux/mac.
Windows has its challenges to run docker desktop, especially win10 Home editions, so you need to really go through the documentation in docker site before installing docker.
WSL too is dependent on Win10, so go as per the documentation given in docker website.
- A Express Application to play with.
I have an express app, created out of express generator hosted on github which i'm going to be using for this exercise.
https://github.com/tirthaguha/card-deck-test
The code on this repo runs on PORT 4000, and exposes API
http://localhost:4000/card-deck/shuffle. This repo makes a call to external APIs, so your system should be enabled to make API calls.
Enough talk, run me the docker
If you are using my repository, don't run npm install. :-O. Lets not waste time here running a simple express app, lets just go straight into using docker.
Create the Dockerfile
Within the repository, create a Dockerfile, and a .dockerignore file, next to package.json
touch Dockerfile
touch .dockerignore
Lets open Dockerfile and add these entries into it.
FROM node:12-slim
# create a directory in your docker image
WORKDIR /app
# install dependencies
COPY ./package*.json ./
# run npm install. you just need the runtime dependencies here
RUN npm ci --only-production
# Copy the rest of the code
COPY ./ ./
# Expose the port, on which your application is running
EXPOSE 4000
# Run the code
CMD [ "node", "./bin/www" ]
Save this Dockerfile.
As you would have guessed already, .dockerignore contains the entries which will be ignored when you're copying all your code on the docker image. Enter the following in the .dockerignore file and save it.
node_modules
npm-debug.log
Build the image
Build your first docker image
docker build -t card-deck-test .
Check the image in your local registry
docker images
It should give you an output like
REPOSITORY TAG IMAGE ID
card-deck-test latest aaaa1111dddd1111
Run the image
docker run -p 4000:4000 -d card-deck-test
The express application is now running on port 4000 in the container, and the container is exposing port 4000. So to summarise, you can now see your application running by opening
http://localhost:4000/card-deck/shuffle on your browser.
What next
Play around with docker
- Run multiple containers simultaneously
docker run -p 4000:4000 -d card-deck-test
docker run -p 4001:4000 -d card-deck-test
docker run -p 4002:4000 -d card-deck-test
then open all of them on browser
http://localhost:4000/card-deck/shuffle
http://localhost:4001/card-deck/shuffle
http://localhost:4002/card-deck/shuffle
- See the containers running
docker ps -a
- Stop the docker container
docker stop [CONTAINER_ID]
- Remove the docker container
docker rm [CONTAINER_ID]
Happy Containerising!
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