Slow Nagios reloads with NDOUtils

[Tom Throckmorton]

On 11/16/2007 04:23 PM, mark.potter at academy.com wrote:

> My first problem, and I am not sure it is actually a problem, is that when 
> I do a reload of nagios (/etc/init.d/nagios reload) it takes, what seems 
> to me to be, a long time. It is usually around 90-120 seconds for Nagios 
> to start allowing use of the web interface once the reload is initiated.

Mark,

I encountered the same issue, spent a while poking at NDO and found that 
tuning down the table trimming options in ndo2db.cfg helped reduce the 
time of this symptom by a third or more, depending on how short of an 
age I chose.  This also cut the user cpu time (taken up by mysqld) by 
about half, as well as the storage and I/O overhead.  YMMV, of course, 
but I found that at this point I don't need to keep the data in those 
very busy tables longer than an hour or so - it'll be *very* useful of 
course when I have an interface that can use that data, but for now, 
keeping it for only a short period is fine.

IANA db expert, but from what I can tell and as Ton suggests, the table 
indexing doesn't appear to be optimal - I see a high 
handler_read_rnd_next count, which usually indicates unnecessary table 
scans).  As far as this particular symptom goes, though, I think it 
might be the indexing in conjunction with the re-sending of retained 
status data that's the culprit here (see the blurb on 'Do not resend 
retained status to NDO' on 
http://altinity.blogs.com/dotorg/2007/09/nagios-patch-da.html)

> We are monitoring:
> 
> # Active Host / Service Checks:272 / 329 
> This doesn't seem like enough to bog down a Dell PowerEdge 1855 with 2GB 
> RAM onboard.

For comparison, I'm running one of our hosts (Nagios 2.10, ndoutils 
1.4b6, MySQL 5.0.22 on CentOS 5, active hosts/services 504/2771), on a 
PowerEdge 1850 w/ 2GB :)  Without any ndo2db tuning, I was seeing around 
a 30-second wait while the status.dat was being recreated (presumably 
waiting on ndomod).  After tuning, I was able to drop that time from ~30 
seconds to between 6-8.

One caveat - if you do choose to trim those ages, you'll note a longer 
pause after the next Nagios restart, as NDO goes about dropping older 
rows.  Once that's complete, be sure to optimize the relevant tables to 
reclaim the unused space.

HTH,

-tt

-- 
Tom Throckmorton
OIT - CSI
Duke University

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