DNS resolution duration
list Josh Luthman
Here is a normal day in the world of Hobbit DNS resolution... DNS statistics: # hostnames resolved : 17 # succesful : 17 # failed : 0 # calls to dnsresolve : 31 DNS lookups completed 1202826251.058136 0.072268 But now when there is a problem reaching the DNS server (I have two in /etc/resolv.conf) it spikes up to... DNS lookups completed 1202825989.913910 40.001908 Is there any way to set the DNS resolution timeout to something smaller? Has anyone tried running bind9 on the Hobbit box itself and having it hold cache locally? I have had two instances where Hobbit failed to resolve DNS for a completely unknown reason, even while the DNS test on the two hosts stay green! What I hope to accomplish is finding the reasoning behind these DNS failures. It will fail to resolve several unrelated domains (different NS servers all together). My real confusion, though, it that Hobbit is asking the same two boxes in /etc/resolv.conf for several domains - some of which resolve, when some don't! Thanks in advance! Josh -- Josh Luthman Office: XXX-XXX-XXXX Direct: XXX-XXX-XXXX XXXX Wayne St Suite XXXX Troy, OH XXXXX Those who don't understand UNIX are condemned to reinvent it, poorly. --- Henry Spencer
list Charles Goyard
Hi,
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Josh Luthman wrote :Is there any way to set the DNS resolution timeout to something smaller? Has anyone tried running bind9 on the Hobbit box itself and having it hold cache locally? I have had two instances where Hobbit failed to resolve DNS for a completely unknown reason, even while the DNS test on the two hosts stay green!
I use pdnsd, it greatly improves response time, especially for http checks (I use a older, libcurl-based version of bbtest-net for http). Some other users also use a local DNS cache with improvements. -- Charles Goyard - user-a6cdca7046e2@xymon.invalid - (+33) 1 45 38 01 31 Orange Business Services - online multimedia // ingénierie
list Tom Georgoulias
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Josh Luthman wrote:
Has anyone tried running bind9 on the Hobbit box itself and having it hold cache locally?
I do, and it works very well. I'm using the caching-nameserver RPM from Red Hat, so choose the appropriate version for your OS and use it. You'll definitely see a reduction in DNS lookup times. It's still worth understanding the lookup failures you are seeing--try adding "--debug" to the bbtest-net command in the [bbnet] section of hobbitlaunch.cfg and check out bb-network.log for more details. Tom
list Josh Luthman
Just be certain we're on the same page, by local DNS we're referring to pdnsd or bind9 being on the same box as the Hobbit daemon, correct?
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On 2/12/08, Charles Goyard <user-a6cdca7046e2@xymon.invalid> wrote:Hi, Josh Luthman wrote :Is there any way to set the DNS resolution timeout to something smaller? Has anyone tried running bind9 on the Hobbit box itself and having it hold cache locally? I have had two instances where Hobbit failed to resolve DNS for a completely unknown reason, even while the DNS test on the two hosts stay green!I use pdnsd, it greatly improves response time, especially for http checks (I use a older, libcurl-based version of bbtest-net for http). Some other users also use a local DNS cache with improvements. -- Charles Goyard - user-a6cdca7046e2@xymon.invalid - (+33) 1 45 38 01 31 Orange Business Services - online multimedia // ingénierie
-- Josh Luthman Office: XXX-XXX-XXXX Direct: XXX-XXX-XXXX XXXX Wayne St Suite XXXX Troy, OH XXXXX Those who don't understand UNIX are condemned to reinvent it, poorly. --- Henry Spencer
list Joe Sloan
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Tom Georgoulias wrote:
Josh Luthman wrote:Has anyone tried running bind9 on the Hobbit box itself and having it hold cache locally?I do, and it works very well. I'm using the caching-nameserver RPM from Red Hat, so choose the appropriate version for your OS and use it. You'll definitely see a reduction in DNS lookup times.
I'm surprised to hear that anyone *wouldn't* be running a local dns server for any unix/linux box running services that require name resolution. It's free, it's easy and speeds performance - a no brainer. Joe
list Henrik Størner
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On Tue, Feb 12, 2008 at 10:52:41AM -0500, Josh Luthman wrote:
DNS lookups completed 1202826251.058136 0.072268 But now when there is a problem reaching the DNS server (I have two in /etc/resolv.conf) it spikes up to... DNS lookups completed 1202825989.913910 40.001908 Is there any way to set the DNS resolution timeout to something smaller? Has anyone tried running bind9 on the Hobbit box itself and having it hold cache locally?
Hobbit does have a tendency of hitting DNS servers pretty hard. I would definitely recommend using a local caching DNS server on your Hobbit box. It is dead simple to setup, and it makes DNS lookups a lot faster and more reliable. As far as the timeouts are concerned, the bbtest-net(1) man-page lists this option: --dns-timeout=N (default: 30 seconds) This assumes you're using Hobbit's built-in resolver library, C-ARES. If you're running bbtest-net with the --no-ares option, there is no way Hobbit can control the DNS lookup settings. Regards, Henrik
list Great D Dilla
As for /etc/resolv.conf, if you have more than 1 DNS servers in the network, putting the following lines "spreads" the load across the servers: option timeout:x (x which is in seconds) option rotate (not having to always query the first nameserver, but to rotate the list) Afterward check if things improve. It did for me before. Of course, having a local caching DNS daemon will be the best solution. Hope this helps you out.
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-----Original Message-----
From: Henrik Stoerner [mailto:user-ce4a2c883f75@xymon.invalid]
Sent: Wednesday, February 13, 2008 5:45 AM
To: user-ae9b8668bcde@xymon.invalid
Subject: Re: [hobbit] DNS resolution duration
On Tue, Feb 12, 2008 at 10:52:41AM -0500, Josh Luthman wrote:DNS lookups completed 1202826251.058136
0.072268
But now when there is a problem reaching the DNS server (I have two in /etc/resolv.conf) it spikes up to... DNS lookups completed 1202825989.913910
40.001908
Is there any way to set the DNS resolution timeout to something smaller? Has anyone tried running bind9 on the Hobbit box itself and having it hold cache locally?
Hobbit does have a tendency of hitting DNS servers pretty hard. I would definitely recommend using a local caching DNS server on your Hobbit box. It is dead simple to setup, and it makes DNS lookups a lot faster and more reliable. As far as the timeouts are concerned, the bbtest-net(1) man-page lists this option: --dns-timeout=N (default: 30 seconds) This assumes you're using Hobbit's built-in resolver library, C-ARES. If you're running bbtest-net with the --no-ares option, there is no way Hobbit can control the DNS lookup settings. Regards, Henrik
list Josh Luthman
Great information! I'll put this stuff into place and come back to this if I have further issues. Thanks a bunch, everyone!
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On 2/12/08, Great D Dilla <user-3e85c7b9d5a4@xymon.invalid> wrote:As for /etc/resolv.conf, if you have more than 1 DNS servers in the network, putting the following lines "spreads" the load across the servers: option timeout:x (x which is in seconds) option rotate (not having to always query the first nameserver, but to rotate the list) Afterward check if things improve. It did for me before. Of course, having a local caching DNS daemon will be the best solution. Hope this helps you out. -----Original Message----- From: Henrik Stoerner [mailto:user-ce4a2c883f75@xymon.invalid] Sent: Wednesday, February 13, 2008 5:45 AM To: user-ae9b8668bcde@xymon.invalid Subject: Re: [hobbit] DNS resolution duration On Tue, Feb 12, 2008 at 10:52:41AM -0500, Josh Luthman wrote:DNS lookups completed 1202826251.0581360.072268But now when there is a problem reaching the DNS server (I have two in /etc/resolv.conf) it spikes up to... DNS lookups completed 1202825989.91391040.001908Is there any way to set the DNS resolution timeout to something smaller? Has anyone tried running bind9 on the Hobbit box itself and having it hold cache locally?Hobbit does have a tendency of hitting DNS servers pretty hard. I would definitely recommend using a local caching DNS server on your Hobbit box. It is dead simple to setup, and it makes DNS lookups a lot faster and more reliable. As far as the timeouts are concerned, the bbtest-net(1) man-page lists this option: --dns-timeout=N (default: 30 seconds) This assumes you're using Hobbit's built-in resolver library, C-ARES. If you're running bbtest-net with the --no-ares option, there is no way Hobbit can control the DNS lookup settings. Regards, Henrik
-- Josh Luthman Office: XXX-XXX-XXXX Direct: XXX-XXX-XXXX XXXX Wayne St Suite XXXX Troy, OH XXXXX Those who don't understand UNIX are condemned to reinvent it, poorly. --- Henry Spencer