On Fri, Nov 1, 2013 at 9:44 PM, Kaan Soral <kaanso...@gmail.com> wrote:

> I've been seeing the errors pop up, but it's always between datetime's
> that differ only by 2-3 seconds
> Than I remembered a *really* old discussion about instance time
> differences and it seems that the cause of these 2-3 second differences is
> instance time differences. Could this be the case?
>


Yes.

Instance clocks are not guaranteed to be accurate - there is always some
skew, especially for large applications which span many instances ( in the
physical sense, span multiple machines which may have some clock drift ).
It's rarely mentioned though, since few applications need that accurate of
a clock.


On Fri, Nov 1, 2013 at 9:44 PM, Kaan Soral <kaanso...@gmail.com> wrote:

> I'm thinking of logging an error only-if the difference is >some_seconds,
> however unsure how many seconds that should be, is there an upper limit to
> this time difference, if it exists?
>
>

When App Engine was still in beta, I personally noted clock skews exceeding
30 seconds, sometimes close to a minute. With that said, instance clocks
seem to be synchronized to a much closer standard nowadays. If I had to
suggest an upper limit for you, I would go with around 10-15 seconds. Note
that I'm not claiming this to be a hard and fast number - it's my rough
approximation. Feel free to ignore it or go with a lower number.


-----------------
-Vinny P
Technology & Media Advisor
Chicago, IL

App Engine Code Samples: http://www.learntogoogleit.com

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