> > What algorithm are you trying to implement that requires synchronized > clocks? To my knowledge it's a pretty well-known best-practice to > never rely on clocks being the same across a distributed system. Some > algorithms can take advantage of closely correlated clocks, but I > believe they never need anything better than the guarantees of NTP > (http://en.wikipedia.org/wiki/Network_Time_Protocol), which is > essentially what App Engine provides. >
My application requires a time stamp from GAE that differs from UTC by no more than 1s. (I'll worry about latencies.) Imagine for example, a global network of sensors that measure geophysical data. The usefulness of the data is degraded if there is a large uncertainty surrounding the sample epoch (timestamp). I'm confused. >> > > Marzia in this thread has already said they dont offer any guarantees. but you say: > ...the guarantees of NTP > (http://en.wikipedia.org/wiki/Network_Time_Protocol), which is > essentially what App Engine provides. NTP is pretty good. Better than 1 second. That would suffice. In summary, my understanding is that GAE does not offer any guarantees about the uncertainty of their server clocks, but they do run NTP. So, when the server clocks are tightly phase-locked to UTC via NTP, all is well. But when they are not sync'd, we'd have no indication that a given timestamp is far from UTC ( > 1s). There are no guarantees that they'd bypass a server that greatly differed from UTC. Is that the state of things? Cesium --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
