[ntp:questions] Time reset

David L. Mills mills at udel.edu
Fri May 2 17:49:32 UTC 2008


Ulrich,

The current (development) code has a new statistics file, called 
protostats, that records significant events, like system peer changes, 
mobilization/demobilization and error events. Among the events is a 
"spike detected" event, which indicates that an offset arrived greater 
than the step threshold (125 ms). Most of the time the spike is one-off 
and is simply discarded. However, if the offset persists beyound the 
stepout threshold (900 s), it will result in a step correction.

Some might interpret the spike event as a warning that a step might 
occur 15 minutes later, but then would have to determine that this is 
indeed not a spike but a legitimate warning. Should it be interreted as 
a warning, it is not at all clear what an application should do. For 
instance, some IBM mainframers recommends that aall pplications should 
be completely shut down during the changeover between standard and 
daylight time. On the other hand, a protostats event triggers a trap, 
which could be caught by a monitoring program that kills power to the 
machine room.

Dave

Ulrich Windl wrote:

> "jkvbe" <jkvbe at NOSPAMyahoo.com> writes:
> 
> 
>>The ntp log file shows when NTP steps the time. But then the potential harm
>>is already done. Especially if the time moves backward, our server might
>>have serious trouble. Is there a log event which indicates that the time is
>>going to be reset in order to enable us to take appropriate action before
>>the actual reset?
> 
> 
> Actually I think: Yes. The symptom typically is a "state" that is different
> from "4" over multiple polling/update intervals (ntpq -c rl).
> 
> Ulrich




More information about the questions mailing list