Re: buildfarm animals and 'snapshot too old'

On 21/05/14 01:42, Tom Lane wrote:
> Andrew Dunstan <andrew(at)dunslane(dot)net> writes:
>> On 05/20/2014 07:09 AM, Tom Lane wrote:
>>> Robert's got a point here. In my usage, the annoying thing is not animals
>>> that take a long time to report in; it's the ones that lie about the
>>> snapshot time (which is how you get "512abc4 in the middle of a bunch of
>>> ef9ab5f's"). That is an issue of incorrect system clock, not of how long
>>> it takes to do the run. I wonder if the buildfarm script could be taught
>>> to get the timestamp from an NTP server somewhere? Or at least
>>> sanity-check the system clock reading by comparing it to the newest commit
>>> timestamp in the git repo.
>> Regarding clock skew, I think we can do better then what you suggest.
>> The web transaction code in the client adds its own timestamp just
>> before running the web transaction. It would be quite reasonable to
>> reject reports from machines with skewed clocks based on this value. I'm
>> not sure what a reasonable skew might be. Somewhere in the range of 5 to
>> 15 minutes seems reasonable.
> Rather than reject, why not take the result and adjust the claimed start
> timestamp by the difference between the web transaction timestamp and the
> buildfarm server's time?
>
> regards, tom lane
>
>
I think, that if possible, any such adjustment should be noted along
with the original time, so that:

1. the timing issue can be remedied
2. it is possible to link the output to any messages in the machines
log etc.

Cheers,
Gavin