mesoneer-tls-certificate-watchbot

A poorman's TLS certificate monitoring system. It leverages GitHub Actions to run a workflow daily to probe the TLS certificate of the sites and notify if the expiration date is near.

How it works

The gist of this is the GitHub Action Workflow tls-certificate-check.yaml in .github/workflows.

It basically, for each defined site, probe its TLS certificate, then -- depends on the expiration date, send a Slack notification if needed.

Sites

All monitored sites are defined in sites.json. The structure is deadly simple:

{
  "sites": [
    { "domain": "example.org", "port" : 443 },
    { "domain": "another.example.org", "port": 8443 }
  ]
}

Monitoring Logs

The workflow will add a Git commit every time it runs (to ensure that the repo is always active). The file executions.jsonl is also appended with a JSON line containing the result of the check.

NOTE: JSONL - https://jsonlines.org/ - is used as it suits the purpose.