On the fly SSL registration and renewal inside Nginx with Let's Encrypt
Nice. Good to see this has a shared storage option (Redis) for load balanced servers. The LE HTTP challenge gives no guarantee which A record it will use. Similarly, if your LB chooses another server even behind the same IP, it'd have to share the challenge state. I haven't read deeply, but I assume it handles the race conditions that can occur with auto renewal (i.e. different servers triggering auto renewal at the same time, overusing LE and hitting the quota faster). It was something I struggled with during the implementation of pluggable storage adapters for Caddy[0].0 - https://github.com/mholt/caddy/pull/913