Any chance to support "max-stale" request header in Varnish?

[Dridi Boukelmoune]

> In fact, the "max-stale" header is almost identical to "grace", except that
> the "max-stale" header is controlled by the client, while the "grace" is

You can't trust clients, so Varnish will not likely honor clients'
claims, like no-cache or max-stale. If you want to give control to the
clients (which I don't recommend for the general case) you have do
painfully do it yourself in VCL. It's a bit tedious to implement.

> controlled by varnish. But still, unless we shut down the backend server,
> there is no way to demonstrate the "grace" for single request either.

There is, you can see the Age header going above the Cache-Control's
mas-age when it happens.