Domain Verification and Troubleshooting Fixing DNS and SSL Issues

Domain Verification and Troubleshooting

After configuring your domain, DNS, and SSL, you need to verify everything works and troubleshoot common issues.

Verification Checklist

# 1. Check DNS resolution
dig yourdomain.com A +short
# Should return: 12.34.56.78

dig api.yourdomain.com A +short
# Should return: 12.34.56.78

# 2. Check HTTP
curl -I http://yourdomain.com
# Should return 301 redirect to HTTPS

# 3. Check HTTPS
curl -I https://yourdomain.com
# Should return 200 with SSL headers

# 4. Check API
curl https://api.yourdomain.com/api/health
# Should return your API response

# 5. Check SSL certificate
echo | openssl s_client -connect yourdomain.com:443 2>/dev/null | openssl x509 -noout -dates
# Should show notBefore and notAfter dates

# 6. Check global DNS propagation
# Visit https://dnschecker.org/
# Enter yourdomain.com, type A

Common Issues and Solutions

1. Domain Not Resolving

Symptom: dig yourdomain.com returns nothing or wrong IP.

Solutions:

# Check nameservers
dig yourdomain.com NS +short
# Should return your DNS provider's nameservers

# Check if the A record exists
dig yourdomain.com A +short
# Should return your EC2 IP

# Flush local DNS cache
sudo dscacheutil -flushcache  # Mac
ipconfig /flushdns             # Windows
sudo systemctl restart nscd   # Linux

Common causes:

• Nameservers not updated at the registrar
• A record not created or wrong value
• DNS propagation not complete (wait 1-24 hours)

2. SSL Certificate Error

Symptom: Browser shows "Your connection is not private" or curl fails with SSL error.

Solutions:

# Check certificate validity
sudo certbot certificates

# Renew if expired
sudo certbot renew

# Check Nginx SSL config
sudo nginx -t

Common causes:

• Certificate expired (renew with certbot)
• Nginx not configured for SSL
• Domain not pointing to the server before certbot was run
• Cloudflare proxy interfering with HTTP-01 challenge

3. 502 Bad Gateway

Symptom: Nginx returns 502.

Solutions:

# Check if Node.js is running
pm2 status

# Check Nginx error log
sudo tail -20 /var/log/nginx/error.log

# Check if port 3000 is listening
sudo netstat -tlnp | grep 3000

# Restart both
pm2 restart devtinder-api
sudo systemctl restart nginx

4. CORS Errors

Symptom: Browser console shows Access-Control-Allow-Origin error.

Solutions:

// Check backend CORS config
app.use(cors({
  origin: ["https://app.yourdomain.com", "https://yourdomain.com"],
  credentials: true
}));

Ensure the origin matches exactly (including https:// and no trailing slash).

5. Cookies Not Being Sent

Symptom: User is not staying logged in.

Solutions:

// Check cookie config
res.cookie("token", token, {
  httpOnly: true,
  secure: true,           // HTTPS only
  sameSite: "none",       // Cross-site (for different subdomains)
  domain: ".yourdomain.com", // All subdomains
  maxAge: 7 * 24 * 60 * 60 * 1000
});

Ensure:

• secure: true is set (HTTPS only)
• sameSite: "none" for cross-subdomain (requires secure)
• domain: ".yourdomain.com" for subdomain sharing
• Frontend Axios has withCredentials: true

6. Redirect Loop

Symptom: Browser shows "Too many redirects" (ERR_TOO_MANY_REDIRECTS).

Solutions:

// In Express
app.set("trust proxy", 1);
// This lets Express know it's behind a proxy (Nginx)
// Now req.protocol returns 'https' correctly

Common cause: Nginx redirects HTTP to HTTPS, and Node.js also redirects because it sees HTTP (from the proxy). Setting trust proxy fixes this.

7. WebSocket Not Working

Symptom: Socket.io connection fails.

Solutions:

# Ensure WebSocket headers are set
location /socket.io/ {
    proxy_pass http://localhost:3000;
    proxy_http_version 1.1;
    proxy_set_header Upgrade $http_upgrade;
    proxy_set_header Connection "upgrade";
}

If using Cloudflare, enable WebSockets in Cloudflare dashboard → Network → WebSockets (on by default).

8. Slow DNS Resolution

Symptom: First request is slow, subsequent requests are fast.

Solutions:

• Reduce TTL (300 seconds for frequently changing records)
• Use a fast DNS provider (Cloudflare is very fast)
• Enable DNS prefetching in your HTML: <link rel="dns-prefetch" href="//api.yourdomain.com">

Useful Tools

The Takeaway

Domain verification involves checking DNS resolution (dig), HTTP to HTTPS redirect (curl -I), SSL certificate validity (openssl), API health, and global propagation (dnschecker.org). Common issues include DNS not resolving (check nameservers and A records), SSL errors (renew with certbot), 502 (Node.js not running), CORS (match origins exactly), cookies not sent (sameSite and domain settings), redirect loops (set trust proxy), and WebSocket failures (check headers).