[Nagiosplug-devel] check_dns.c

[Awais Ahmad]

Hi,

Does anyone see any utility in rewriting check_dns.c to use gethostbyname(),
instead of nslookup?. 
Also, is just just querying for an A record really enough functionality for
a plugin which checks name servers?

Cheers

Awais

-----Original Message-----
From: Voon, Ton [mailto:Ton.Voon at egg.com]
Sent: Tuesday, September 30, 2003 8:55 AM
To: 'Karl DeBisschop'
Cc: NagiosPlug Devel
Subject: RE: [Nagiosplug-devel] RFC: OS specific ifdefs in main plugin
cod e


> -----Original Message-----
> From: Karl DeBisschop [mailto:karl at debisschop.net] 
> Sent: Tuesday, September 30, 2003 5:58 AM
> To: Ton Voon
> Cc: NagiosPlug Devel
> Subject: Re: [Nagiosplug-devel] RFC: OS specific ifdefs in 
> main plugin code
> 
> 
> On Mon, 2003-09-29 at 10:46, Voon, Ton wrote:
> > Hi! Wanted to get some opinions on the latest development 
> of the plugins.
> > 
> > I'm starting to use OS specific ifdefs to get system data and I was
> > wondering if this is the right way to go. The latest 
> version of check_swap.c
> > has ifdefs for Solaris and AIX as they have different ways 
> for checking
> > swap. It could have been done via ./configure, but there 
> are too many
> > different possibilities (for instance, need to run 
> different switches for
> > individual partition checks versus a summary of swap). 
> > 
> > If it was done via ./configure, you'd also need to set 
> flags to say whether
> > to ignore first lines (some have header info, others 
> don't), work out
> > different format responses (some return megabytes, some 
> return free, some
> > return percentage).
> > 
> > I think all this is easier done within the code itself. Is this bad?
> 
> What I don't like is use of targets like #ifdef _AIX or #ifdef sun --
> for instance, SGI IRIX also has a swap command with very 
> similar syntax.
> Except it is in /sbin instead of /usr/sbin. It's not at all obvious to
> me why we needs sun-specific code, but not IRIX-specific code (or more
> to the point, why can't we write generic code that tests whether the
> swap command accepts the '-s' switch, and forgo the #ifdef sun.

The reason for the sun specific code is that swap -l does not report
"allocated but not used" swap, thus giving "wrong" results on free
(available) swap. This is only available with swap -s. There was a thread on
this about 9 months back.

The trouble with IRIX which "also has a swap command with very similar
syntax" is that the syntax is similar but not the same. So we would have to
have ./configure work in parsing the output differently. But sometimes it is
more than just the sscanf order: there is also if there is a header line, if
the syntax returns MBs or bytes or percentage, if the results are for free,
used or total.

I guess these could be abstracted out to a generic function, but then the
parameters to this function will probably need to be written very
"code-like", so why not use code?

> 
> To use things like #ifdef sun, unless absolutely needed, would seem to
> require perfect knowlege of all Uinx-like OS's in use, and perfect
> knowlege of those extensions that do not yet exist.
> 
> Often, this is a symptom that there is a basic problem. In fact, we
> really see this issue in 3 plugins: check_ping, check_procs, and
> check_swap.
> 
> From my point of view, we should be using a C API in POSIX for these
> functions, rather than trying to parse comannd-line utilities.

I agree, but these are not always readily available hence the hackery.
Eventually, I guess nagiosplug is basically a command-line way of getting a
common result from all OSes.

> 
> Certainly we can write a check_icmp, and probably should. If we can
> identify an apporpriate API for swap and procs, we should do the same
> for them. If not, I am much more ready to accept OS-specific 
> ifdefs for
> procs than I am for swap. There are only a handful of swap variants.

I only have Solaris, AIX and Darwin knowledge and they all handle swap
differently (Darwin doesn't even preallocated swap space - it just
dynamically grows).

check_procs doesn't have any ifdefs, maybe because the abstration is
better/easier. Even so, I've had to add in extra variables to ./configure
like number of columns to get round some inconsistencies (AIX's ps does not
have an RSS field).

> AFAICT, if there ar n varieties of Unix, there must be n+1 
> varieties of
> the ps command.
> 

If we continue with the ifdef method, in future we could abstract out as we
understand the different cases better.

Ton


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