heads-up: trap avalanche depletes swap and leads to killing Nag, Apache, named, ...

[Stanley Hopcroft]

Dear Sir,

I am writing to thank you very much for your letter and say,


On Thu, May 15, 2003 at 09:33:57AM +0200, Tom DE BLENDE wrote:
> 
> Was flap detection enabled for that passive service? Shouldn't flap 
> detection prevent that notification flood?

I am very grateful for your helpful suggestion.

I have enabled the global config directive in nagios.cfg and await with
much interest the next occurrence.

<offtopic>

I have been writing some very unsafe and inefficient CGIs recently that
today subjected the Nag host to a 1-1.5X memory over-commit (3-400 MB
when RAM + swap == 512 MB).

Apart from the OS killing the apache child running the CGI, all was
well. It appears that the most dangerous thing is a large number of
processes rather than a few big ones

</offtopic>

Thanks for the heads up about this.

Nag is simply __stuffed__ with sophisticated innovations such as this
(and freshness checking).

Given that the docco suggests (in at least two places) that

'Before I go any futher, let me say that flapping detection has been a
little difficult to implement. How exactly does one determine what "too
frequently" means in regards to state changes for a particular host or
service?

When I first started looking into flap detection I tried to find some
information on how flapping could/should be detected. After I couldn't
find any, I decided to settle with what seemed to be a reasonable
solution. The methods by which Nagios detects service and host state
flapping are described below...'

this is a new innovation, how well does it work ?


> 
> Kind regards,
> Tom
> 

Yours sincerely.

-- 
------------------------------------------------------------------------
Stanley Hopcroft
------------------------------------------------------------------------

'...No man is an island, entire of itself; every man is a piece of the
continent, a part of the main. If a clod be washed away by the sea,
Europe is the less, as well as if a promontory were, as well as if a
manor of thy friend's or of thine own were. Any man's death diminishes
me, because I am involved in mankind; and therefore never send to know
for whom the bell tolls; it tolls for thee...'

from Meditation 17, J Donne.


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