Brad Nicholson wrote:
>> Andrew Sullivan wrote:
>>> On Sat, Jan 12, 2008 at 05:51:57PM -0800, Jeff Frost wrote:
>>>> You might check the slon logs for any indication this is what caused your 
>>>> problem.  I thought slon did its work based entirely on xxid, but I could 
>>>> be wrong.  Perhaps one of the developers will comment.  In any event, I'm 
>>>> sure you know the clocks should be in sync as a best practice.
>>> Not entirely based on xxid, no.  They can't be synced across nodes.  You
>>> _must_ be nntp-synced between your nodes.  They should peer from one
>>> another, and _then_ get their time from some other source.
>> I want to be sure I understand this: Are you saying that a few milliseconds
>>  of time skew between servers will make Slony fail?
>>
> 
> No, it won't.  There is always going to be some minor skew, even when
> synced with NTP.

Then why is it required to run  nntp between nodes, and only have one external connection to a time server?  Even using independent connections to a time service, the various Slony hosts keep their clocks very closely synchronized.  If a few milliseconds doesn't matter, then it seems to me that an ordinary ntpd(1) should be good enough.

Is there an actual spec for "how much time skew is too much" for Slony?  Like, "All hosts must have their clocks synced within 100 msec."  Or is it just a "good idea" that's not formalized?

What are the consequences of having to servers with out-of-sync clocks?

Thanks,
Craig