[Check_mk (english)] Unresolvable race condition in 'ntp' check code.

Mathias Kettner mk at mathias-kettner.de
Wed Feb 22 18:15:05 CET 2012


Hi Matthew,

I've now removed the according condition from the check. I do not think
that it is very important anyway.

Mathias


Am 25.11.2011 19:56, schrieb Stier, Matthew:
> Part of the ‘ntp’ check code (/usr/share/check_mk/checks/ntp) tests to
> see if the seconds since last poll results (when) is less than 2 times
> the current poll interval (poll).
>
> A race condition exists when there is a transition from a high to low
> ‘poll’ interval, a high ‘when’ count created by the previous high poll
> interval.
>
> What happens is that while the ‘poll’ interval is reduced immediately,
> there may be a delay to when the next poll is initiated, it’s response,
> and the resetting of the ‘when’ counter; in that interval Nagios can run
> an NTP check and will get a false failure. The follow up check by Nagios
> one minute later clears the failure, but, the false failure will already
> have been logged, and fault/recovery notifications sent.
>
> This happens with my three primary NTP servers (with their clock sources
> across a 70ms round trip WAN link) three to four times per day. My only
> solution so far, is to comment out the test condition, and it’s single
> line conditional block of code.
>
>
>
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