[Nagiosplug-devel] Working on testcases

[Ton Voon]

On 4 Nov 2005, at 07:39, sean finney wrote:

> hi ton,
>
> On Thu, Nov 03, 2005 at 03:14:18PM +0000, Ton Voon wrote:
>> - if a server does not exist, it looks like check_tcp uses usage2 to
>> alert the error. This returns a status of UNKNOWN. The tests
>> currently check for CRITICAL. Which should it be? The plugin
>> documentation says UNKNOWN is: "Invalid command line arguments were
>> supplied to the plugin or the plugin was unable to check the status
>> of the given hosts/service", which does suggest hostname invalid, but
>> then I'm worried that Nagios needs to be specifically configured to
>> alert on unknown states.
>>
>> Any thoughts?
>
> my thought is that for most plugins (except the dns-related ones),
> UNKNOWN seems a proper state.  chances are there's something
> monitoring DNS that will issue a CRITICAL anyway.  however, i don't
> feel to comitted to this opinion and would be interested to hear
> the counter-argument.

My "bad" scenario:

   - Nagios configured to alert on critical/warning - but not unknown  
- for a check_http on wiki.internal.company.com
   - Nagios also configured for critical on check_dns to check  
nameserver, but not specific wiki.internal.company.com record
   - Someone deletes the DNS entry for wiki.internal.company.com by  
mistake
   - Nagios says check_dns is okay (nameserver still running)
   - check_http on wiki.internal.company.com returns UNKNOWN because  
cannot resolve hostname
   - however, no alert. Sys admin gets b0ll0cked for not spotting  
problem :(

Three ways to fix at the configuration level:
   - check_http against IP address, but then removes point of DNS
   - alert on unknown, but then what's the point of unknown?
   - for each hostname used, configure a check_dns for it. But that  
sounds like a huge (and unobvious) overhead

Cons to using CRITICAL:
   - if DNS goes, all services that rely on hostname lookup via DNS  
will go CRITICAL and flood alerts (but that, I think, is an obvious  
reaction)

Am I worrying too much?

Ton


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