Re: [squid-users] cache_peer weighting

Tony Dodd wrote:
> Adrian Chadd wrote:
>> Ok cool. Now, the techie questions:
>>
>> * according to the draft, the port isn't used as part of the hash, is
>> this
>> right?
>
> Indeed; and there's no newer version of the draft, unfortunately.
> According to CARP draft v1, the only place the port is stored, is in the
> ASCII Proxy Array Membership Table.
> For anyone who hasn't seen the draft, it's available at
> http://www.linofee.org/~jel/da/mmb99/7/CarpSpec.html

Squid is a little different in its peer requirements. The peering needs
to be anchored off the name= parameter or in the absence of that the
peer ip/fqdn given. In squid THAT must be unique for several other
indexes similar to this.
There is no requirement in squid that the IP/http-port combo be unique
because the IP/icp-port combo may be the difference.

>>
>> * is just adding the port to the hash the "right way" of doing it?
>> (its a hash, so you want to create even distributions..)

no. see above.
name= being more arbitrary could be more even in best-case than port,
worst-case is about the same.

>
> I think it's important to get the port involved in the hashing as early
> on as possible, as the CARP mechanism is based off adding a URL hash +
> proxy hash together to achieve a high score.

True enough, just the port being the wrong anchor for squids peering table.

> Equally, there's the issue
> of getting a wide enough hash distribution; however, looking at the data
> I'm logging, with the combination of URL+proxy hash, the results are
> extremely wide and varying, so I don't think it is breaking anything -
> that said, it is 7am, and I am tired, so hopefully someone else can
> agree/disagree on this point.
>
>> * do people have a problem with this going into squid, with relevant
>> documentation
>> being written about how CARP has been "extended" like this?

A hash alteration is clearly needed, just the details of what.

Amos

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