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Re: set up monin and mydns dns-server


From: Martin Pala
Subject: Re: set up monin and mydns dns-server
Date: Sun, 9 Sep 2007 22:57:10 +0200

The connection tests without specific protocol perform just:

1.) in the case of TCP perform connect - when established, test is OK and connection is closed

2.) in the case of UDP send one byte and in the case that no error is returned, the test passed (UDP is stateless and when protocol is not specified it is not possible to say whether the packet was delivered and processed when nothing is returned


In your case it means that no error was returned in the case of UDP and the TCP connection was established (i.e. your DNS server is not fully dead - it accepts connections, but probably doesn't process requests).

In such case, you will need:

1.) either custom DNS protocol test (source is in protocols/dns.c, patches are welcomed ;)

2.) or if you want to use existing monit's DNS test, configure your DNS server to return NS record for root nameservers


Martin


On Sep 9, 2007, at 6:34 PM, Samuel Vogel wrote:

I tried to not specify the protocol, but it doesn't work.
MyDNS stops answering queries, but monit doesn't notice that!
This is how my config file looks:

# cat /etc/monit/monitrc
set daemon 20
set logfile syslog facility log_daemon

check process mydns with pidfile /var/run/mydns.pid
       start program = "/etc/init.d/mydns start"
       stop program = "/etc/init.d/mydns stop"
       if failed port 53 type udp then restart
       if failed port 53 type tcp then restart
       if 5 restarts within 5 cycles then timeout

Maybe the problem is, that mydns is still running, but just stops answering queries since of an unresolved bug!

Regards,
Samy

Martin Pala schrieb:
This could be good to add. I think it can take ca. 4-8 hours. Patches are welcomed ;)

As workaround for such DNS servers it is possible to use generic tcp/udp checks (don't specify the 'protocol' option).

Martin


On Sep 5, 2007, at 6:16 PM, monit user wrote:

Many (most?) non-bind DNS server software will fail the dns protocol test in monit as it is written (dbjdns, mydns and a couple others that I tested so far), AFAIK because bind includes a "default" referral response to a query about the root servers. Even the great and powerful Paul Vixie admitted that this is something that most servers shouldn't be doing and others pointed out non-broken client resolver libraries will reject/throw out such a response.

The relationship between BIND and some of the DNS RFCs act a good example of why it sucks to take a certain application's behavior and codify it as a set of standards, as we are currently experiencing with OOXML.

To work across all DNS servers, the test should have the following options:

Protocol: UDP or TCP
Query Type: A, NS, etc
and if you care about the exact value of the response rather than the fact that there was or was not a response from the server an "expect" or "checksum" section for checking the response.

Can this go on the list? http://www.tildeslash.com/monit/doc/ next.php
or how do things get on the list?

How many hours do you think it would take to add a parameterized dns test?

Samuel Vogel wrote:
I would really like to do this, but actually I can only code python and php and my C skills hardly can accomplish more than writing a few if's and initializing variables... I could provide alle the infos somebody of the mydns team would need to accomplish this task. Since a DNS check is allready there, I'd hope there is only a small problem, that needs to be fixed.
Regards,
Samy
Jan-Henrik Haukeland schrieb:
On 5. sep. 2007, at 08.07, Samuel Vogel wrote:

The logs point me to the Porblem, that mydns somehow fails the DNS Test, even thou it answers all querys normaly

An excellent opportunity for you to create a patch of monit's dns test @ protocol/dns.c :-)


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