Poul-Henning Kamp <[EMAIL PROTECTED]> writes:
> I would appreciate if you call could take a moment to look at this
> diagram and see if it makes sense:
>
>       http://phk.freebsd.dk/misc/varnish.png

It certainly is a lot more readable than the complete diagram
(http://phk.freebsd.dk/misc/varnish.gif).

I assume all the red arrows point to vcl_error()?

> The plot has gotten simpler, partly because I did it by hand instead
> of using dot(1), but more so because I found out that I needed to
> trust VCL to do more things.

Absolutely.

>     vcl_hash{}
>       Place holder for the idea that it might be desirable to
>       hash on more or different fields than (URL+Host:).
>
>       Not fully thought through yet, may or may not happen.

Strictly speaking, you need to hash on every header mentioned in
Vary:, but you don't even have that information until you've retrieved
at least one version of the document from the backend - and even then,
when a new request comes in, you need to identify the requested
document to know which headers to hash on - so it looks like we need a
two-level hash.

>     vcl_hit{}
>       Not really sure what you would do here, but you get
>       the chance if you dream up something.
>
>       One possible thing would be to react to high hitrates
>       and initiate compression.

...or check the time remaining before expiry and initiate a prefetch?
You don't mention vcl_timeout, which in any case isn't called until
after the document has expired.

DES
-- 
Dag-Erling Smørgrav
Senior Software Developer
Linpro AS - www.linpro.no
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