Thanks to Node.js - Millions of frontend developers that write JavaScript for the browser are now able to write the server-side code in addition to the client-side code without the need to learn a completely different language. Node.js is a free, open-sourced, cross-platform JavaScript run-time environment. It is capable to handle thousands of concurrent connections with a single server without introducing the burden of managing thread concurrency, which could be a significant source of bugs.
In this quickstart guide, you will see how to build a Node.js application (visitor counter) using Nginx, Redis and Docker.
.
├── docker-compose.yml
├── redis
├── nginx
│ ├── Dockerfile
│ └── nginx.conf
├── web1
│ ├── Dockerfile
│ ├── package.json
│ └── server.js
└── web2
├── Dockerfile
├── package.json
└── server.js
– Install Docker Desktop
Use Docker's install guide to setup Docker Desktop for Mac or Windows on your local system.
Docker Desktop comes with Docker compose installed by default, hence you don't need to install it separately.
Create an empty file with the below content and save it by name - "docker-compose.yml"
version: '3.9'
services:
redis:
image: 'redis:alpine'
ports:
- '6379:6379'
web1:
restart: on-failure
build: ./web
hostname: web1
ports:
- '81:5000'
web2:
restart: on-failure
build: ./web
hostname: web2
ports:
- '82:5000'
nginx:
build: ./nginx
ports:
- '80:80'
depends_on:
- web1
- web2The compose file defines an application with four services redis, web1, web2 and nginx. When deploying the application, docker-compose maps port 80 of the web service container to port 80 of the host as specified in the file.
By default, Redis runs on port 6379. Make sure you don't run another instance of Redis on your system or port 6379 on the host is not being used by another container, otherwise the port should be changed.
upstream loadbalancer {
server web1:5000;
server web2:5000;
}
server {
listen 80;
server_name localhost;
location / {
proxy_pass http://loadbalancer;
}
}FROM nginx:1.21.6
RUN rm /etc/nginx/conf.d/default.conf
COPY nginx.conf /etc/nginx/conf.d/default.confFROM node:14.17.3-alpine3.14
WORKDIR /usr/src/app
COPY ./package.json ./
RUN npm install
COPY ./server.js ./
CMD ["npm","start"]
"name": "web",
"version": "1.0.0",
"description": "Running Node.js and Express.js on Docker",
"main": "server.js",
"scripts": {
"start": "node server.js"
},
"dependencies": {
"express": "^4.17.2",
"redis": "3.1.2"
},
"author": "",
"license": "MIT"
}const express = require('express');
const redis = require('redis');
const app = express();
const redisClient = redis.createClient({
host: 'redis',
port: 6379
});
app.get('/', function(req, res) {
redisClient.get('numVisits', function(err, numVisits) {
numVisitsToDisplay = parseInt(numVisits) + 1;
if (isNaN(numVisitsToDisplay)) {
numVisitsToDisplay = 1;
}
res.send('Number of visits is: ' + numVisitsToDisplay);
numVisits++;
redisClient.set('numVisits', numVisits);
});
});
app.listen(5000, function() {
console.log('Web application is listening on port 5000');
});Let us deploy the full-fledged app using docker-compose:
$ docker-compose up -dCreating nginx-nodejs-redis_redis_1 ... done
Creating nginx-nodejs-redis_web1_1 ... done
Creating nginx-nodejs-redis_web2_1 ... done
Creating nginx-nodejs-redis_nginx_1 ... doneListing the running containers. You should see three containers running and the port mapping as below:
docker-compose ps
Name Command State Ports
------------------------------------------------------------------------------------------
nginx-nodejs-redis_nginx_1 /docker-entrypoint.sh ngin Up 0.0.0.0:80->80/tcp
...
nginx-nodejs-redis_redis_1 docker-entrypoint.sh redis Up 0.0.0.0:6379->6379/tcp
...
nginx-nodejs-redis_web1_1 docker-entrypoint.sh npm Up 0.0.0.0:81->5000/tcp
start
nginx-nodejs-redis_web2_1 docker-entrypoint.sh npm Up 0.0.0.0:82->5000/tcp
startAfter the application starts, navigate to http://localhost in your web browser or run:
curl localhost:80
curl localhost:80
web1: Total number of visits is: 1curl localhost:80
web1: Total number of visits is: 2$ curl localhost:80
web2: Total number of visits is: 3$ curl localhost:80
web2: Total number of visits is: 4If you want to monitor the Redis keys, you can use the MONITOR command. Install redis-cli on your Mac system using brew install redis and then directly connect to Redis container by issuing the following command:
% redis-cli
127.0.0.1:6379> monitor
OK
1646485507.290868 [0 172.24.0.2:34330] "get" "numVisits"
1646485507.309070 [0 172.24.0.2:34330] "set" "numVisits" "5"
1646485509.228084 [0 172.24.0.2:34330] "get" "numVisits"
1646485509.241762 [0 172.24.0.2:34330] "set" "numVisits" "6"
1646485509.619369 [0 172.24.0.4:52082] "get" "numVisits"
1646485509.629739 [0 172.24.0.4:52082] "set" "numVisits" "7"
1646485509.990926 [0 172.24.0.2:34330] "get" "numVisits"
1646485509.999947 [0 172.24.0.2:34330] "set" "numVisits" "8"
1646485510.270934 [0 172.24.0.4:52082] "get" "numVisits"
1646485510.286785 [0 172.24.0.4:52082] "set" "numVisits" "9"
1646485510.469613 [0 172.24.0.2:34330] "get" "numVisits"
1646485510.480849 [0 172.24.0.2:34330] "set" "numVisits" "10"
1646485510.622615 [0 172.24.0.4:52082] "get" "numVisits"
1646485510.632720 [0 172.24.0.4:52082] "set" "numVisits" "11"