cert-manager

cert-manager is an open-source Kubernetes add-on that treats certificates and certificate issuers as native cluster resources. Instead of requesting, installing and renewing TLS certificates by hand, operators declare what they need and the controller obtains and maintains it, which reduces the chance of an outage caused by an expired certificate.

It can issue certificates from several sources, including Let's Encrypt through ACME, HashiCorp Vault and CyberArk Certificate Manager, as well as from an issuer running inside the cluster itself. It also watches expiry dates and attempts renewal at a suitable time before a certificate lapses. A common use is securing Ingress resources automatically.

The project is written in Go and released under the Apache-2.0 license. It runs inside your own cluster, with several installation methods documented on cert-manager.io, plus a getting started guide and a quick start for nginx-ingress. Community help is available through the Kubernetes Slack channels and the issue tracker.