On Wednesday 04 June 2014 at 21:03, Nidal Shater wrote:
> I read about "log_fqdn"
>
> Turn this on if you wish to log fully qualified domain names
> in the access.log. To do this Squid does a DNS lookup of all
> IP's connecting to it. This can (in some situations) increase
> latency, which makes your cache seem slower for interactive
> browsing.
>
> Is this very bad to the performance or it has a little effect, because of
> DNS looks up ?
That's an impossible question to answer with any accuracy, because it depends
on how efficient the DNS lookups are.
If most of your lookups are answered locally (which is likely, if all your
clients are local and you've got DNS well set up), they'll be very quick and
you'll notice very little performance difference.
If most of your lookups result in timeouts or 'not found', then you'll notice
a bad effect on performance.
Also, if you run a local caching DNS server (which of course you really should
be doing with Squid in any case, just for the forward lookups), then no matter
whether your clients are local or remote, you should fairly quickly get an
efficient lookup cache which answers the queries about your clients' IPs.
My advice - try it and see how it works out on your network, with your
clients:
1. Use the standard logging, measure the load on your Squid server, and the
latency of web accesses under "normal" usage conditions.
2. Turn on log_fqdn, measure the load and the latency again under as similar
conditions as you can manage, and see whether you're bothered about the
difference.
Regards,
Antony.
--
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