Docker Compose Tutorial

Docker Compose tutorial for nodejs app and nginx reverse_proxy

NodeJS server

Create a app directory and generate a file index.js.

Contents of index.js

// index.js
const express = require('express');
const app = express();
app.get('/', (req, res) => {
  res.send('Hello World!')
})
app.listen(5000, () => console.log('Server is up and running'));

To test the application you can open the terminal and run

node index.js

A nodejs server is initialized at http://localhost:5000

Creating Dockerfile A text file with image assembling instruction for docker. Create a blank file in the app directory and named it Dockerfile, this will automatically change the filetype. Under Dockerfile insert the following context.

# pull the Node.js Docker image
FROM node:alpine

# create the directory inside the container
WORKDIR /usr/src/app

# copy the package.json files from local machine to the workdir in container
COPY package*.json ./

# run npm install in our local machine
RUN npm install
RUN npm install express
# copy the generated modules and all other files to the container
COPY . .

# our app is running on port 5000 within the container, so need to expose it
EXPOSE 5000

# the command that starts our app
CMD ["node", "index.js"]

In addition create .dockerignore file to speed up the docker build.

node_modules
npm-debug.log

Nginx Docker

server {
    location / {
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header X-Forwarded-Proto $scheme;

        proxy_pass http://nodeserver:5000;
    }
}

Dockerfile

FROM nginx
COPY default.conf /etc/nginx/conf.d/default.conf

Docker-Compose

This tool will allow us to start multiple containers with single command script. Moreover, it builds a common netwrok between containers for container-container communication. To generate this file, create an empty file in the main directory (outside app directory) and rename it to docker-compose.yml. This file will contain the configuration of each container and services. Detailed documentation for docker compose can be found on the following Link.

There are two containers being created in the below file, nodeserver which will run our application and nginx this will be the reverse proxy & load-balancer. Under each container we have build variable which will build the image using the dockerfile present in each directory (app and nginx). Second variable is ports, for nodeserver we are forwardign internal (docker) port 5000 to 80 and our nginx is listening on port 80 on both ends.
Docker-compose file:

version: "3.8"
services:
    nodeserver:
        build:
            context: ./app
        ports:
            - "5000:80"
    nginx:
        restart: always
        build:
            context: ./nginx
        ports:
            - "80:80"

Now, run the following command to start the containers:

Linux (Ubuntu) docker-compose up --build

Windows docker compose up --build

This should start your application at Link.