README.md

Containerize Reactjs Application

Here we will employ a multi-stage build process to containerize a react application. The stages are as follows:-

Multi-stage build pipeline

• STAGE 1: Building assets using node image
• STAGE 2: Using nginx to serve the built assets

Let's begin with stage 1. We'll start with a node base image node:14 and alias it as builder. It will be explained later why the aliasing was done.

FROM node:14 AS builder

Afterward, we'll set up the working directory. We'll use /app as the working directory but you can name it something else as well.

WORKDIR /app

Now, we'll copy the package.json and yarn.lock (or package-lock.json) to the working directory (/app) and install all the node modules using yarn install (or npm install). This will create a node_modules with all the dependency files.

COPY package.json .
COPY yarn.lock .
RUN yarn install

Once the node modules are installed, the contents of the current directory (.) will be copied over to the image's working directory (/app). Notice that the current environment may contain a node_modules folder and copying all contents will override the existing node_modules folder inside the docker image's working directory. So, this folder needs to be ignored. This can be done by creating a .dockerignore file in the root directory of the application and adding the line "node_modules". Once the copying is complete, the yarn build (or npm run build) will be executed to build all the assets in the /build directory.

COPY . .
RUN yarn build

NOTE: it is possible to achieve the same result by copying over all the contents from the current directory to the docker image's /app directory and executing yarn build && yarn install directly. However, copying the package.json & yarn.lock and installing the node modules before starting the building process has an added advantage. It essentially allows the docker to cache the downloaded files. This allows a faster build time in the subsequent build of the application.

COPY . .
RUN yarn install && yarn build 

Now, let's begin stage 2 of the deployment process. Deploying a nodejs application with nginx can allow for various performance gains. Nginx can be used to implement reverse proxy, cache static files, load balancing etc. We start from nginx:alpine base image and change the image's working directory to /usr/share/nginx/html. nginx uses this directory to serve the content therefore we need to put the built files that were generated previously on stage 1. Before doing so we need to clean our current directory.

FROM nginx:alpine
WORKDIR /usr/share/nginx/html
RUN rm -rf ./*

Now, we'll copy all contents of /build directory of the image environment in stage 1. To do so, we need to somehow reference that building stage. In stage 1, we used 'FROM ... AS ...' syntax to reference the stage as builder. Using --from=builder we can reference that stage and copy all the content to stage two's working directory i.e. /usr/share/nginx/html. Finally, we set the entry point to start serving the application.

COPY --from=builder /app/build .
ENTRYPOINT ["nginx", "-g", "daemon off;"]

So, let's start by creating our first image. We can check if an image or container is already present using the following commands To check for images

docker images 

To check for running and stopped containers

docker ps
docker ps -a 

No results were shown suggesting that no container is present. Now, we need to be in the root directory (/dockerize-reactjs-app) of the app to start building our image.

docker build -t react-nginx:1 . 

This will show the following output in the terminal.

You can see above that the overall build process was divided into 12 steps. Once the build process is done you can see the image using the following

docker images

You can see that a new repository was created by the name react-nginx with an image id of d01fb5c13587. We'll be using this image id to create our image. Now, in order to build the container from our image file, we need to add the following command

docker run d01fb5c13587

This will use the image with d01fb5c13587 to build the container. Although this command will spin up the image we won't be able to see the web app as the container by default inaccessible to outside world (in this case our local machine). So, we need to expose a port of the container and map it to our local machine's port to see our app in action. we will map port 7001 of our local machine to container's port 80 as nginx by deafult listens to port 80.

docker run -p 7001:80 d01fb5c13587

Now, if you open the browser and type http://localhost:7001/ you'll see the deployed app. Hurray, you've done it!

You can type Ctrl + C to stop the container. To check the stopped container type

docker ps -a

Now, if you want to get rid of the container, you need to use the following

docker rm 8c270816ffbb

where 8c270816ffbb is the container id. By doing this the container will be removed.

We can also remove the image that was used to create the container using the following command

docker rmi d01fb5c13587

This will remove the image.

Also, you can directly use the docker-compose.yml file to create the image and spin up the container just by using following command:-

docker compose up

THANKS FOR READING