backend/director admin states

[Nils Goroll]

Hi,

On 02/05/18 17:07, Guillaume Quintard wrote:
> I think I could live with "auto" meaning "dependent/probe" depending on the type
> of object.

Me too, but I also think that for varnishadm backend.list output, displaying the
actual facts is significantly more helpful.

> Not sure the disabled case is super useful. If I get what you say, the only
> thing differing from setting it to sick is that we keep using the open
> connections, instead of finishing in-flight requests. Is it worth it?

No, the suggestion is regarding a different level: Consider some application
server backends with local session store: Using shard / hash / explicit vcl, you
have implemented some kind of persistence such that requests with the same
session id always get sent to the same backend.

Now you plan to restart that backend and want to still send requests with
existing persisted session ids to it, but no requests without a session cookie.

One current way to do this is to essentially define every backend twice and use
once director for the "existing session" and one for the "no session" case.
Other options probably involve std.healthy(), the backend probe and retries.

I think we can do much better than this.

> I'd argue "deleted" should be "dead", just to complete the medically depressing
> vocabulary list you started :-)

wfm.

> (and we'll need to bring back "saint" from the dead)

Greetings from the guy who currently tries to keep the saint's mode working with. ;)

Nils