[Freeswitch-dev] Epoch current time difference

[Anthony Minessale]

As a caveat, DST being only one example, the other more real reasons
include: erroneous commands from sysadmins changing the system time,
 virtual migrations over VE and many other reasons that went into our
decision to lock on to the most accurate time source possible ASAP.


On Wed, Dec 14, 2011 at 10:49 AM, Michael Giagnocavo <mgg at giagnocavo.net>wrote:

> Daylight saving should never modify the time, as for anything like this,
> one should be using UTC time, or local time with a UTC offset. Any software
> that computes a duration differently because of DST cannot blame the
> system: it is very, very, broken. (Although, I’ll bet there’s more than one
> company out there with broken CDR software. In fact, I came across such a
> program and asked the developers about it. They said “not a problem; the
> system crashes when there’s a DST shift, so we never have to deal with
> those records.”)****
>
> ** **
>
> The only reason I can think of for the time values to jump around is if
> your clock is way out of sync and you force a large NTP jump. But in that
> case, you’re sorta out of luck anyways.****
>
> ** **
>
> -Michael****
>
> ** **
>
> *From:* freeswitch-dev-bounces at lists.freeswitch.org [mailto:
> freeswitch-dev-bounces at lists.freeswitch.org] *On Behalf Of *Anthony
> Minessale
> *Sent:* Wednesday, December 14, 2011 9:32 AM
> *To:* freeswitch-dev at lists.freeswitch.org
> *Subject:* Re: [Freeswitch-dev] Epoch current time difference****
>
> ** **
>
> I feel I have explained this many times.  Too bad it never makes it to a
> wiki or faq.****
>
> ** **
>
> Allowing any software to trust the system time is very dangerous.
>  Something that was depending on the system time to calculate a duration
> etc can be considerably compromised if the time suddenly changes by hours
> or years in either direction.****
>
> Things like daylights savings time can break CDR etc.****
>
> ** **
>
> The clock in FS is the onboard monotonic clock and the offset to real time
> is preserved.  If you want FS to sync to system time when desired there are
> commands to perform this operation.****
>
> ** **
>
> On Wed, Dec 14, 2011 at 10:21 AM, Cavalera Claudio Luigi <
> Claudio.Cavalera at italtel.it> wrote:****
>
> > -----Original Message-----
> > I don't know what your environment is like, but if you can get away
> > with keeping NTP running on the server and issue a sync_clock nightly,
> > that might be the best thing.  I can think of 3 or 4 other systems
> > that could fail unexpectedly due to time drift like that.  At the very
> > least, it makes it so that all of your logs have correct timestamps :)
> >
> > Gabe****
>
> Hello,
> sorry for "hijacking" this thread.
> Can someone please explain why FS keeps its own time ?
> As far as I know on vmware machines you can't avoid using NTP if you
> want to keep your system clock and with automatic daylight changes i've
> seen a difference of one hour between system time and freeswitch time.
> :-(
>
> Ciao,
> Claudio
>
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> Anthony Minessale II
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-- 
Anthony Minessale II

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