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Ivan
Ivan

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Build a Microservice to Monitor SSL

#ssl #node #n8n

Monitor SSL Certificates (and Get Alerts Automatically)

If you manage websites or deal with infrastructure, you know that forgetting to renew an SSL certificate can cause serious trouble: downtime, security warnings, and loss of trust.

To solve this, I built a lightweight microservice in Node.js that checks the SSL validity of any domain — and can be fully automated using n8n.

What is this microservice?

It’s a simple HTTP API with one endpoint:

GET /check?host=yourdomain.com
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It returns the SSL certificate status:

{
  "domain": "yourdomain.com",
  "valid": true,
  "expires_on": "2025-07-10T12:00:00.000Z",
  "days_remaining": 25
}
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If the domain is invalid or unreachable:

{
  "domain": "invalidsite.com",
  "valid": false,
  "error": "getaddrinfo ENOTFOUND invalidsite.com"
}
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It uses only native Node.js tls and the express library. Fast and efficient.

How to use it

Clone the repo, install dependencies, and run:

npm install
npm start
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Then visit:

http://localhost:2999/check?host=yourdomain.com
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Automating with n8n

The real power comes with automation using n8n — a visual workflow automation tool.

With it, you can:

  • Run scheduled checks (every 12h, 20min, etc.)
  • Monitor multiple domains in batch

  • Send alerts via email or Slack when:

    • The SSL is about to expire
    • The domain is down
    • There's a DNS or connection error

  • Log all responses into a MySQL database (for reporting or analytics)

💡 I included a pre-configured .json workflow you can import into n8n and customize.

Real-world scenario

Say you manage 35 websites and subdomains.

With this microservice + n8n, you can:

  • Monitor all domains on autopilot
  • Get alerts before users report issues
  • Stay in control without spreadsheets or expensive monitoring services

Requirements

  • Node.js 18+
  • PM2 (optional, for running it as a service)
  • n8n (optional but highly recommended)

Project structure 

.
├── server.js              ← main microservice code
├── package.json
├── README.md
├── site_ssl_monitor.json  ← n8n workflow
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Final thoughts

This microservice solves a common pain for developers, sysadmins, and IT teams — in a simple, free, and self-hosted way.

If you enjoy automation, security, and full control over your tools, this is for you.

➡️ GitHub repo

If you find this helpful, leave a comment or follow me for more smart tools like this.

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