Re: How to vary URL length?

From: Alex Rousskov (rousskov@measurement-factory.com)
Date: Wed Aug 14 2002 - 22:33:33 MDT


On Wed, 14 Aug 2002, Larry Creech wrote:

> I have a cluster of caching boxes that MCARP, and whose cache based
> of URL length. I noticed that while the load is evenly distributed
> with webaxe-4 the URL's are of the same length causing my cache to
> become unbalanced and heavily loaded onto a single server. Is there
> an easy solution or configuration parameter I could set to vary the
> URL length to get a more even distribution of cache and loading
> within the cluster?

Yes, there is an easy way to get highly variable URL length. Using
mime field of Content PGL type, you can specify URL path prefix and/or
suffix. Both can be selected from a user-defined distribution of
strings. The set of string values can probably be quite large without
affecting Polygraph performance. You could generate those strings with
a script if needed. Try not to use letter 'w' in prefix strings
(Polygraph uses that character to optimize search for object IDs
embedded in a URL).

Here is a simple PGL example

        Content cntExample = {
                mime = {
                        prefixes = [
                                "images/": 11%,
                                "x-" : 22%,
                                "could-be-quite-long/if/needed": 33%,
                                "cgi-bin/"
                        ];
                        extensions = [
                                "short": 10%,
                                "quite/long" : 20%,
                                "this/one/is-very-long/indeed": 30%,
                                ".html"
                        ];
                };
                ...
        };

If the above is not good enough, please let me know. We can add a
URL-length-randomization feature.

Thanks,

Alex.

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