Certificate Expiry Monitor is a utility that monitors TLS certificate expiration dates and exposes this information as Prometheus metrics. The tool can be deployed as a Docker container and provides configurable monitoring of certificate expiry times across multiple domains. The monitor supports various deployment scenarios including Kubernetes environments where it can automatically discover domains from ingresses across specified namespaces. It offers flexible configuration options for polling frequency, domain inclusion/exclusion patterns using regex support, and connection security settings. Key features include: - Automatic domain discovery from Kubernetes ingresses - Configurable polling intervals for certificate checks - Domain filtering with regex pattern support for exclusions - Prometheus metrics export for integration with monitoring systems - Docker containerization for easy deployment - Support for both secure and insecure TLS connections - Host IP connection mode for pod-based deployments The tool accepts comma-separated domain lists for manual configuration and can exclude specific domains or domain patterns from monitoring. It integrates with existing Prometheus-based monitoring infrastructure to provide visibility into certificate expiration status across an organization's TLS-enabled services.