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Re: good practice for clients



N.G.Smith wrote:
> 
> Martin Hamilton says
> >"N.G.Smith" writes:
> >
> >| For those who don't follow uk newsgroups, this comes after some heated
> >| discussion, where I was trying to encourage users of caches to accept
> >| the fact that they were at least partly to blame in the case where
> >| their WWW access was interrupted by their browser's inability to
> >| degrade gracefully in the light of a proxy failure.
> >
> >Well, you did kind of imply that everyone ought to be running Netscape >
> >= v2 ! <ducks>
> 
> Or encouraging their browser authors to implement more sensible behaviour.

I now consider myself suitably encouraged and have implemented a partial
solution to this in my browser.

> >I may be being pointing the finger at the wrong culprit here, though - 
> >perhaps it's the browser or the TCP/IP implementation which isn't doing 
> >anything with those multiple IP addresses, and they are all being 
> >returned by the DNS lookup ?
> 
> I'd guess that it is mostly the browsers. In any case the browser can
> always do another lookup.

I've implemented a load-balancing scheme whereby when the initial DNS
lookup is done for wwwcache.hensa.ac.uk, all 4 IP addresses are added to
my internal cache.  This buffer is then rotated every time the table is
consulted, and upon certain types of connection failure, a retry with a
different address is used and the failed address removed from the address
cache, until such a time as there are none left, at which point a new DNS
lookup will be performed.   However, there is no fallback to using the
direct connection to target host yet.

Is this the right sort of strategy to be following?  It certainly seems to
work, but it's hard to test the resilience without a partial failure of
the cache.

-- 
Stewart Brodie, Electronics & Computer Science, Southampton University.
http://www.ecs.soton.ac.uk/~snb94r/      http://delenn.ecs.soton.ac.uk/


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