Reload origincert without a restart

[abeluck]

Feature request

Add the ability to reload the origincert file without restarting the daemon, ideally via SIGHUP signal.

Motivation

We want to rotate origin origin certs frequently. This requires editing the origincert file and then restarting cloudflared. This causes all in-flight requests from our users to be dropped.

More background

We use cloudflared for Argo Tunnels on our hosts. We do not use cloudflared login, but rather provision the argo tokens and origin certs separately and copy them to the hosts. We do this because it is more secure then the default which issues a wildcard cert.

[adamchalmers]

Sounds like a useful feature. We'd accept a PR if you wanted to write one!

[abeluck]

I can hack my way around, but I don't have much experience with Go unfortunately :( I'd probably need some hand-holding.

I grepped through the codebase and found this:

https://github.com/cloudflare/cloudflared/blob/master/tlsconfig/certreloader.go

Is CertReloader related to this issue?