Re: [squid-users] round robin DNS and the occassional failing IP.

On Mon, 25 Feb 2008, Henrik Nordström wrote:

> mån 2008-02-25 klockan 17:30 +1100 skrev Tim Connors:
>
> > So it's already meant to be doing this (by caching bad status, I presume
> > you mean it doesn't keep trying that ip?)? Is that perhaps in the 3.x
> > branch? One host that has this wrong is an ancient distribution with
> > 2.5.STABLE14 on it (sigh), but the other is a 2.6.18-1+b1 in debian's
> > versioning scheme.
>
> It's been doing that for many many years.
>
> But not very effective with a site like Google that says "please forget
> everything you know about my IPs ever 5 minutes".

Odd.

According to
dig +recurse +additional +authority +notrace A google.com.au
(which I freely admit I could be using wrong, or my upstream ncsd server
on the host I am on now and exhibited these problems before, could be silly)
the TTL here starts off reasonably low[1], I get 3 IPs, it counts to 0,
resets to half an hour, and I keep getting the 3 same IPs. Mind you, I
know nothing about DNS, so I could be looking at the wrong thing.

But that doesn't stop the fact that squid still tries to keep contacting
the dead host whether that 5-30 minutes has expired or not. Can't
reproduce the fault now naturally, since I've got good hosts in my DNS
cache, but does the tcpdump in this bug report show that precisely this is
*not* happening?

http://www.squid-cache.org/bugs/show_bug.cgi?id=2239

[1]
> dig +recurse +additional +authority +notrace A google.com.au

; <<>> DiG 9.2.4 <<>> +recurse +additional +authority +notrace A google.com.au
;; global options: printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 52053
;; flags: qr rd ra; QUERY: 1, ANSWER: 3, AUTHORITY: 4, ADDITIONAL: 4

;; QUESTION SECTION:
;google.com.au. IN A

;; ANSWER SECTION:
google.com.au. 869 IN A 72.14.235.104
google.com.au. 869 IN A 64.233.167.104
google.com.au. 869 IN A 72.14.207.104

;; AUTHORITY SECTION:
google.com.au. 24503 IN NS ns4.google.com.
google.com.au. 24503 IN NS ns1.google.com.
google.com.au. 24503 IN NS ns2.google.com.
google.com.au. 24503 IN NS ns3.google.com.

;; ADDITIONAL SECTION:
ns4.google.com. 14233 IN A 216.239.38.10
ns1.google.com. 1121 IN A 216.239.32.10
ns2.google.com. 1121 IN A 216.239.34.10
ns3.google.com. 1121 IN A 216.239.36.10

;; Query time: 12 msec
;; SERVER: 192.231.166.63#53(192.231.166.63)
;; WHEN: Tue Feb 26 21:55:31 2008
;; MSG SIZE rcvd: 225

-- 
Tim Connors