How to reduce a very high latency number

[Greg Cope, e-DBA Team]

On Wed, 2006-05-24 at 04:53 -0400, Morris, Patrick wrote:
> How are you guys running the nsca daemon?  I've got systems that perform
> thousands of checks with no problem.
> 
> I'm looking at a system right now that submits over 5300 checks to a
> central server running nsca via xinetd, and it has a average service
> latency of .153 secs. 

Are you not referring to the server end?  I am running nsca as a daemon.

We are referring to the client end that sends the results.

Greg 

> -----Original Message-----
> From: nagios-users-admin at lists.sourceforge.net
> [mailto:nagios-users-admin at lists.sourceforge.net] On Behalf Of Greg Cope
> Sent: Wednesday, May 24, 2006 1:47 AM
> To: Jacob Ritorto
> Cc: nagios-users at lists.sourceforge.net
> Subject: Re: [Nagios-users] Re: How to reduce a very high latency number
> 
> Jacob,
> 
> I noticed the same thing today.
> 
> We run a few distributed servers that do about 150 checks (at the
> moment) and submit this to our central server.
> 
> That's allot of send_nsca processes that get spawned.
> 
> I like you fix!
> 
> send_nsca would not appear to be scallable for those running lots of
> passive checks with distributed systems.
> 
> Greg
> 
> On Tue, 2006-05-23 at 09:48 -0400, Jacob Ritorto wrote:
> > Greetings,
> >        A colleague of mine (poctum) and I ran into something like this
> 
> > while using nsca and have crafted a similar solution.  We observed 
> > that send_nsca was sending only one result to the central Nagios 
> > server per connection.  Testing revealed that send_nsca was capable of
> 
> > handling thousands of results per connection.  Sending only one at a 
> > time was resulting in lots of dropped data because there were 
> > nominally about 5 results derived per second.  We enabled 
> > aggregate_status_updates in the nagios.cfg file, but this yielded no 
> > improvement in the result submissions.  BTW, this is Nagios-2.2 and
> > nsca-2.6 on Solaris 10.  Our workaround is a quick and dirty but 
> > efficient solution.  It may not be as refined as trask's and relies on
> 
> > nuances of unix file handling algorithms to get the job done.  That 
> > said, it's working perfectly for us.  As this seems to work well, but 
> > may violate Ethan's design intentions, your feedback/input is 
> > requested.  Deploy at your own risk.
> > 
> > Jacob Ritorto, Lead UNIX Server Operations Engineer InnovationsTech
> > 
> > Here's our solution:
> > 
> > 1) Altered last line in
> > /opt/nagios/libexec/eventhandlers/submit_check_result thusly.  It 
> > basically concatenates check results to a temp file.
> > 
> > #/bin/printf "%s\t%s\t%s\t%s\n" "$1" "$2" "$return_code" "$4" | 
> > /opt/nagios/bin/send_nsca 172.16.x.x -c /opt/nagios/etc/send_nsca.cfg
> > 
> > /bin/printf "%s\t%s\t%s\t%s\n" "$1" "$2" "$return_code" "$4" >> 
> > /opt/nagios/var/results.waiting
> > 
> > 
> > 2) Created a daemon process called reap (managed by smf, but it has 
> > been up for a month so far, so may be ok as an init.d script) to pull 
> > aside the aforementioned temp file (results.waiting) every five 
> > seconds and send the bits off to the central Nagios server (note that 
> > original file is re-created immediately via step 1 above).  This 
> > probably only works perfectly on unix & unix-like systems due to the 
> > nature of files hanging around intact until the last program 
> > referencing them has exited.  It's been some time, but the last I 
> > checked, DOS/WINxxxx doesn't treat files this way.  Here's the simple 
> > little reap daemon:
> > 
> > # cat /opt/nagios/bin/reap
> > #!/usr/bin/tcsh
> > while (1)
> >  sleep 5
> >  mv /opt/nagios/var/results.waiting /opt/nagios/var/results.sending  
> > cat /opt/nagios/var/results.sending | /opt/nagios/bin/send_nsca 
> > 172.16.x.x -c /opt/nagios/etc/send_nsca.cfg >/dev/null end
> > 
> > 
> > Summary:  Slave Nagios servers now store up check results in the temp 
> > file for 5 seconds, then they get shipped off to nsca on the central 
> > Nagios machine in one swoop instead of one-at-a-time.
> > 
> > 
> > *~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~
> > 
> > 
> > 
> > From: Trask <trasko at gm...>
> > Re: How to reduce a very high latency number
> > 2006-05-23 03:50
> > 
> > On 5/22/06, srunschke at abit.de <srunschke at abit.de> wrote:
> > > nagios-users-admin at lists.sourceforge.net schrieb am 17.05.2006
> 20:09:16:
> > >
> > > To me this is obviously a performance issue related to hardware.
> > > Your machines have way too few RAM. It is totally not possible to 
> > > run 1800 checks on a 512MB machine in a timely manner.
> > >
> > 
> > I figured this out this past Saturday.  It is not any lack of the 
> > hardware.  I was seeing negligible load nor an excessive use of 
> > memory.  No configuration change I made seemed to have any appreciable
> 
> > effect on the latency times I was getting.  I ended up doing a "top"
> > with 1 second intervals and just watching it for awhile.  I noticed 
> > that sometimes there would be a good number of nagios processes 
> > 20-30-40 or so, but the majority of the time there were only 2, 3 or 4
> 
> > processes.  Although I do not know exactly *why* this was happening, 
> > it ends up the during the time where there was 2-4 processes running,
> > 2 of them were always the"submit_passive_check" script and 
> > "send_nsca".  It appears that this is being done serially (ie not in
> > parallel) and ends up blocking subsequent checks until they are done.
> > I would see these 2 processes running (with steadily increasing PIDs) 
> > for up to a minute and then a short-lived (4-5 seconds) "explosion" of
> 
> > nagios processes (service/host checks).  After this flurry of 
> > activity, it would be another 60 seconds or so of just 2-4 processes.
> > 
> > I resolved this problem by changing by "submit_passive_check" script.
> > Below are some sample scripts, both old and new.  The short of it is 
> > like this:  Previously, the "submit_passive_check" script did a printf
> 
> > of the data in the appropriate format and piped it to the "send_nsca"
> > command (in a shell script).  I have eliminated this bottleneck by 
> > having "submit_passive_check" redirect its output to a named pipe and 
> > then having another script feed "send_nsca" with that data as it comes
> 
> > in to the named pipe.
> > 
> > Latency times have dropped from the 600-700 seconds to 0.2 seconds on 
> > the worst server and from 45-55 seconds to 0.06 on the 2nd to worst.
> > That's more like it!
> > 
> > Below are a few scripts w/ notes as to what each one is.  Thanks to 
> > everyone who offered help.



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