README.md

docker-swarm-nodejs

a sample of Docker Swarm with nodejs

Create a new folder called testimony.

$ cd testimony

Create a new file index.js and paste the code below :

var http = require('http');
var os = require('os');

http.createServer(function (req, res) {
    res.writeHead(200, {'Content-Type': 'text/html'});
    res.end(`<h1>I'm ${os.hostname()}</h1>`);
}).listen(8080);

Create Dockerfile

Now we need to dockerize the app, we’ll create a file named Dockerfile with the following code:

FROM node
RUN mkdir -p /usr/src/app
COPY index.js /usr/src/app
EXPOSE 8080
CMD [ "node", "/usr/src/app/index" ]

Build the Docker image

To build a docker image of our newly awesome Node.js app from the docker file instructions; we’ll write the docker build command line, where our Dockerfile file is located:

$ docker build -t testimony .

Let's run

Now we have a docker image of our simple (and awesome) Node.js app, and we can create containers from that image.

Let's say we want 20 running containers of that image and all behind a load balancing server. For our HTTP server we’ll use HAProxy that will listen to port 85 Let’s create a docker-compose.yml file:

version: '3'

services:
  testimony:
   image: testimony
   ports:
     - 8080
   environment:
     - SERVICE_PORTS=8080
   deploy:
     replicas: 20
     update_config:
       parallelism: 5
       delay: 10s
     restart_policy:
       condition: on-failure
       max_attempts: 3
       window: 120s
   networks:
     - web

  proxy:
    image: dockercloud/haproxy
    depends_on:
      - testimony
    environment:
      - BALANCE=leastconn
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock
    ports:
      - 85:80
    networks:
      - web
    deploy:
      placement:
        constraints: [node.role == manager]

networks:
  web:
    driver: overlay

Docker SWARM !!!!!

Now let’s create a swarm (with one computer for now, but you can easily add more to the swarm). To do this we'll write docker swarm init and we created a swarm!!

docker swarm init

It’s also added our current computer to the swarm, and since our computer is the first it’s also the manager of the swarm.

Let's build the stack with the following comand line :

docker stack deploy --compose-file=docker-compose.yml production

We are doing two things : 1 - Build the services 2 - deploy them to our local stack called production

Once done you browse http://localhost:85 and see the nodejs message,

Hitting F5 will display a different hostname since HAproxy will load balance the request.