Persistent "admin" state/backend health

[Dridi Boukelmoune]

> So, we're trying to find a way of preserving the "admin" states across restart/reload/crashes.
> We're thinking about reusing vagent2, or creating another intermediate above the Child, but I'm wondering first if this is not better suited in Varnish Core as a basic feature? But then, where?

Since 4.1 backends are owned by VCLs so it's no longer possible to
preserve the state across reloads. You could however make your own
reload script that could collect the backends state from the active
VCL and apply it to the new VCL between vcl.load and vcl.use.

Dridi