Re: Best way to reduce load on DNS server??

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From: Jeff Cochran (jcochran.nospam_at_naplesgov.com)
Date: 04/09/04 

Date: Fri, 09 Apr 2004 03:52:53 GMT

On Wed, 07 Apr 2004 09:43:03 -0400, Iain Simpson
<dummyaddress@sympatico.ca> wrote:

>On Wed, 07 Apr 2004 13:06:58 GMT, jcochran.nospam@naplesgov.com (Jeff
>Cochran) wrote:
>
>>You always use the same address. Once you look it up the first time,
>>it's cached and you don't look it up again until the TTL expires or
>>your cache flushes. Whether you look it up in DNS or Hosts makes no
>>difference here.
>>
>>Hosts will be queried before DNS. If the name is resolved there,
>>there is no DNS request made.
>
>Thanks for your replies Jeff.
>
>This makes sense on one level, but not on another.
>
>I use a piece of software called Privoxy to refresh the relevant
>section of the webpage every second. Privoxy creates a log file giving
>details of each request made. Generally that stream involves requests
>to refresh.betfair.com. As you can see these requests are being
>successful but suddenly a request to the same domain
>(refresh.betfair.com) fails with a "could not resolve hostname" error.
>>From what you have said, that would suggest the TTL for
>refresh.betfair.com must be zero, i.e. a DNS lookup is required every
>request? Otherwise how could it fail having been cached? If the TTL is
>zero, would a hosts entry for refresh.betfair.com be a big help in
>reducing the requests to the DNS server?

Just because it's cached doesn't mean something won't prevent it from
reading the cache. Nor does it prevent another type of error that
your app reports as being unable to resolve the name.

Jeff

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