If the GAE server clocks can be out of sync several seconds it could potentially be a problem for my messenger/chat application. Let's say that user A sends a message and user B replies to that message within 10 seconds, then if user A and B access different servers when sending their messages with an out of sync of more than 10 seconds, then message B can as I understand it get a timestamp that is EARLIER than message A, resulting in an incorrect ordering of the messages.
On Dec 22 2008, 7:59 pm, Marzia Niccolai <ma...@google.com> wrote: > Hi, > > Please see this > thread:http://groups.google.com/group/google-appengine/browse_thread/thread/... > > Generally one would expect the clocks to be synced within a few seconds, but > there are not any guarantees of any kind. > > -Marzia > > On Mon, Dec 22, 2008 at 4:20 AM, rvjcallanan <vinc...@callanan.ie> wrote: > > > I recall reading somewhere that, due to global time differences across > > servers, we cannot rely on timestamps to draw certain conclusions > > about GAE data e.g. operation sequence, etc. > > > Time synchronisation is a critical issue in any distributed app yet I > > have been unable to get hard facts and figures on how well Google > > synchronises its servers globally. > > > I assume some form of NTP syncing is performed so I would expect that > > steady state drift will be of the order of milliseconds across the > > globe. But what if a server is rebooted or added to the Google > > network? Will this server be disabled until it has reached a certain > > sync level. > > > In a nutshell, a few questions... > > > 1. How accurate are Google server clocks re: some global standard? > > 2. What is the maximum drift between servers? > > 3. Is tighter synchronisation guaranteed between servers in a local > > data centre servicing entity groups > > > TIA, > > > rvjcallanan --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Google App Engine" group. To post to this group, send email to google-appengine@googlegroups.com To unsubscribe from this group, send email to google-appengine+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/google-appengine?hl=en -~----------~----~----~----~------~----~------~--~---
