max_concurrent_checks=0 not working on 3.2.1 (maybe earlier versions, too)?

[Adam Augustine]

I think what he is saying is that setting it to zero limited the
number of checks to 200, while increasing it to 1,000,000 caused it to
execute more than 200, which would seem backwards if 0 basically means
"do as many as you possibly can" (based on CPU).

This would indicate that max_concurrent_checks=0 is limiting it to
some number rather than using all the CPU possible, which sounds like
a bug.

On Wed, Apr 14, 2010 at 2:40 PM, Max <perldork at webwizarddesign.com> wrote:
> Your server can only run so many checks at once, so setting it to 0
> only says 'cap parallel check limits by what the CPU can do.'
>
> On our dual quad-core CPU hosts with 8 GB RAM we get about 350 checks
> running in parallel max at any given instant after restart; 90-92% of
> our checks take less than 1 second to complete (most are SNMP-based).
>
> We do attempt to have as many checks run as possible by setting
> max_concurrent to 0 and by tweaking the next check time for all checks
> to be the same second so that Nagios does attempt to run as many
> processes as it possibly can at once.
>
> Were you actually seeing your system start up 10,000 processes at once
> with max_concurrent_checks set to 10,000?  That would be perfectly
> reasonably if this were an Erlang-based system :), if you are getting
> that number of processes at a given timel at the OS level, what kind
> of system are you running on?  Impressive.
>
> - Max
>
> On Wed, Apr 14, 2010 at 4:03 PM, Cary Petterborg
> <PetterborgCa at ldschurch.org> wrote:
>> We have been experimenting with 3.2.1 before deploying it in our production environment. When we first started up Nagios 3.2.1 with max_concurrent_checks=0 (which the documentation says should put no limit on the number of concurrent checks), we only got about 200 checks completed per minute. Since we have 37,600 services, this led to quite a high latency.
>>
>> It attempting to increase the number of checks I decided to play with max_concurrent_checks to see what would result. I went from 0 to 1000, then to 10,0000, then to 100,000 then to 1,000,000(+) for the value. It increased the number of checks per minute with each larger number, until I got to 1,000,000, where it no longer made any difference.
>>
>> So, my conclusion is that max_concurrent_checks=0 is not working properly. Can anyone else verify that this is the case?
>>
>>
>>
>> Cary Petterborg
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