✅ Task
Display a Docker Swarm cluster with 3 nodes
📦 Create the API
Folder: swarm-api
swarm-api/Dockerfile
FROM node:22.13-alpine
WORKDIR /app
COPY package*.json ./
RUN npm install && npm audit fix --force
COPY . .
EXPOSE 3000
CMD ["node", "main.js"]
swarm-api/package.json
{
"name": "swarm-api",
"version": "1.0.0",
"main": "main.js",
"license": "MIT",
"dependencies": {
"express": "^5.1.0",
"pg": "^8.16.0"
}
}
swarm-api/main.js
const express = require('express');
const { Pool } = require('pg');
const app = express();
const port = process.env.PORT || 3000;
const pool = new Pool({
host: process.env.PGHOST || 'postgres',
user: 'postgres',
password: process.env.PGPASSWORD || 'secret',
database: 'postgres',
port: 5432,
});
app.get('/', async (req, res) => {
const result = await pool.query('SELECT NOW()');
res.json({ message: 'Hello from API', time: result.rows[0].now });
});
app.listen(port, '0.0.0.0', () => {
console.log(`API running on port ${port}`);
});
🛠️ Build the Docker image
docker build --tag rhonalchirinos/hello-api:latest .
☁️ Push to Docker Hub
docker login
docker push rhonalchirinos/hello-api:latest
🌐 Create an Overlay Network
docker network create -d overlay hello-net
ℹ️ Why an overlay network? Overlay networks allow containers and services to communicate across multiple Docker nodes in a Swarm. This eliminates the need for OS-level routing.
🐳 Initialize Docker Swarm
docker swarm init
➕ Add Worker Nodes to the Swarm
docker swarm join --token SWMTKN-1-xxxxx 192.168.64.6:2377
📌 You can get the worker token using:
docker swarm join-token worker
🛢️ Create a PostgreSQL Service
docker service create \
--name postgres \
--env POSTGRES_PASSWORD=secret \
--mount type=volume,source=testdb,target=/var/lib/postgresql/data \
--network hello-net \
postgres
🚀 Deploy the API Service in Swarm
First, check if services are listed:
docker service ls
Then create the service:
docker service create \
--name some-api \
--replicas 3 \
--publish 3000:3000 \
--network hello-net \
rhonalchirinos/hello-api:latest
You can inspect the published ports with:
# inspect ports
docker service inspect some-api --format '{{json .Endpoint.Ports}}' | jq
🧪 Test the API
curl <http://localhost:3000>
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