Fly.io Hello World

Overview

Deploy a minimal app to Fly.io using fly launch. Fly.io runs Docker containers on Firecracker microVMs across 30+ regions worldwide. Two paths: flyctl CLI (simple) or Machines API (programmatic).

Instructions

Step 1: Launch with flyctl

# Create a new directory with a Dockerfile
mkdir fly-hello && cd fly-hello

cat > Dockerfile << 'EOF'
FROM node:20-alpine
WORKDIR /app
COPY server.js .
EXPOSE 3000
CMD ["node", "server.js"]
EOF

cat > server.js << 'EOF'
const http = require('http');
const server = http.createServer((req, res) => {
  res.writeHead(200, { 'Content-Type': 'application/json' });
  res.end(JSON.stringify({
    message: 'Hello from Fly.io!',
    region: process.env.FLY_REGION,
    app: process.env.FLY_APP_NAME,
  }));
});
server.listen(3000, () => console.log('Listening on :3000'));
EOF

# Launch — creates app, generates fly.toml, deploys
fly launch --name hello-fly --region iad --now

Step 2: Verify Deployment

# Check status
fly status

# Open in browser
fly open

# View logs
fly logs

# Test with cURL
curl https://hello-fly.fly.dev/
# {"message":"Hello from Fly.io!","region":"iad","app":"hello-fly"}

Step 3: Deploy via Machines API

const FLY_API = 'https://api.machines.dev';
const headers = {
  'Authorization': `Bearer ${process.env.FLY_API_TOKEN}`,
  'Content-Type': 'application/json',
};

// Create an app
const app = await fetch(`${FLY_API}/v1/apps`, {
  method: 'POST',
  headers,
  body: JSON.stringify({
    app_name: 'hello-api',
    org_slug: 'personal',
  }),
}).then(r => r.json());

// Create a machine in the app
const machine = await fetch(`${FLY_API}/v1/apps/hello-api/machines`, {
  method: 'POST',
  headers,
  body: JSON.stringify({
    region: 'iad',
    config: {
      image: 'nginx:alpine',
      services: [{
        ports: [{ port: 443, handlers: ['tls', 'http'] }],
        protocol: 'tcp',
        internal_port: 80,
      }],
      guest: { cpu_kind: 'shared', cpus: 1, memory_mb: 256 },
    },
  }),
}).then(r => r.json());

console.log(`Machine ${machine.id} created in ${machine.region}`);

Output

Machine e784079f004d86 created in iad
App URL: https://hello-api.fly.dev

Error Handling

Resources

• Fly Launch
• Deploy an App
• Machines API

Next Steps

Proceed to flyio-local-dev-loop for development workflow setup.