[google-appengine] Re: time and date sync service in google cluster
Hi cryb, Obviously we do our best to ensure system time is accurate on all our machines. However, it's simply impossible to keep a large number of machines sufficiently well in sync that you can rely on montonicity (that values will only increase with time) across the service based solely on a wall-clock. If your app needs strictly increasing time for its operation, wall clock time alone will not provide that. -Nick Johnson On Thu, May 28, 2009 at 7:39 AM, cryb cbuti...@gmail.com wrote: Hello. Although it should be obvious, the Google cluster should provide a time and date synchronization service for all its nodes. I've done some search on the internet and I went through appengine docs, but I didn't find any reference that states this. I know that this should be common sense, but I just want to make sure. So my question is: does google cluster guarantees time and date sync among its nodes? I ask this because I need it for expiration primitives that won't work properly if such a service is not in place. Thanks. --~--~-~--~~~---~--~~ 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 -~--~~~~--~~--~--~---
[google-appengine] Re: time and date sync service in google cluster
Hey cryb, Going by a *very* shoddy test a few months ago, _most_ nodes seem to be within a second of each other, although I did get one or two requests that were +/- 10 seconds off average. Based on that, it's fair to expect around one second's accuracy most of the time. In any case, I've since changed my own app's design such that it doesn't have a reliance on accurate timing from AppEngine, and I believe many designs can be changed similarly. If you need microsecond accuracy, you're probably building on the wrong platform. :-) David 2009/5/28 cryb cbuti...@gmail.com: Hello. Although it should be obvious, the Google cluster should provide a time and date synchronization service for all its nodes. I've done some search on the internet and I went through appengine docs, but I didn't find any reference that states this. I know that this should be common sense, but I just want to make sure. So my question is: does google cluster guarantees time and date sync among its nodes? I ask this because I need it for expiration primitives that won't work properly if such a service is not in place. Thanks. -- It is better to be wrong than to be vague. — Freeman Dyson --~--~-~--~~~---~--~~ 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 -~--~~~~--~~--~--~---
[google-appengine] Re: time and date sync service in google cluster
So my question is: does google cluster guarantees time and date sync among its nodes? IIRC, the last time this came up, the answer was no. They expect the times on different nodes wil be somewhat synchronized and reasonably close to correct, but make no guarantees. On May 28, 7:39 am, cryb cbuti...@gmail.com wrote: Hello. Although it should be obvious, the Google cluster should provide a time and date synchronization service for all its nodes. I've done some search on the internet and I went through appengine docs, but I didn't find any reference that states this. I know that this should be common sense, but I just want to make sure. So my question is: does google cluster guarantees time and date sync among its nodes? I ask this because I need it for expiration primitives that won't work properly if such a service is not in place. Thanks. --~--~-~--~~~---~--~~ 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 -~--~~~~--~~--~--~---
