Varnish regular expression evaluated at compile time.

[Hugues Alary]

Hi Paul,

Thank you for your answer, and your idea. It is a very good idea I didn't
think of.

I don't know if it's gonna be the solution I'll adopt, but at this very
moment I only have that or coding a vmod. However I don't think that coding
a vmod is a solution as I would just implement something (regular
expression evaluation at run time) that phk says being too expensive.

-Hugues

On Wed, Oct 10, 2012 at 3:59 PM, Paul A. Procacci <pprocacci at datapipe.com>wrote:

> Everything you stated is true.  Without inline C or a vmod
> the only alternative I know of to accomplish this would be
> to dynamically generate the parts of your config that
> depend on the sha1 of a url.
>
> For instance, you could use something similar to the following:
>
> #################################################
> #!/usr/bin/perl -w
>
> use strict;
> use Digest::SHA qw(sha1_hex);
>
> my @files = qw!/index.html /homepage.html!;
>
> my $output;
> my $seen = 0;
> foreach(@files){
>   if($seen++){
>     $output .= "else";
>   }
>   $output .= "if(req.url == \"$_\"){\n";
>   $output .= "  set resp.http.Set-Cookie = \"foo" . sha1_hex($_) . "=\" +
> random.get_rand();\n";
>   $output .= "}\n"
> }
>
> print $output;
> #################################################
>
> Modified to your liking obviously, which results in the following
> output:
>
> #################################################
> if(req.url == "/index.html"){
>   set resp.http.Set-Cookie =
> "foo14fe4559026d4c5b5eb530ee70300c52d99e70d7=" + random.get_rand();
> }
> elseif(req.url == "/homepage.html"){
>   set resp.http.Set-Cookie =
> "foo6593125bb8fade312b1081d4ee1998f316aa4081=" + random.get_rand();
> }
> #################################################
>
> This has the benefit that everything with exception to the random
> number is computed ahead of time, but has the drawback of having
> to use in this case, another script to maintain a list of
> accessible files to generate their hash.
>
> Honestly not sure if this is going to help or not, but
> maybe it'll give you other ideas to explore.
>
> ~Paul
>
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-- 
Hugues ALARY
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