> I think I can live without uniqueness as > long as timestamps don't go backwards.
Timestamps on a given server probably don't go backwards, but there's no guarantee about the relationship between clocks on different servers. On Jul 13, 11:16 pm, n8gray <n8g...@gmail.com> wrote: > Hi Albert, > > Thanks for the suggestion. I think I can live without uniqueness as > long as timestamps don't go backwards. But I think my problem still > exists with a sharded counter. Having a counter is certainly better > than using datetime.utcnow() and lets me assign an order to all events > that have been generated, but that's not really the problem. The > tricky part is deciding, on the client end, which events to request > based on the events you've received. When the client asks for "all > events after time T" it gets some "last" event with a new timestamp > S. But I don't think you can trust this S because there might be some > other event in some corner of GAE with an earlier timestamp that > hasn't yet been observed by the server that answered the client's > request. > > I guess the root of the problem is that I know that transactions on > entity groups give me the ACID properties but when it comes to > operations outside of transactions I have no idea what the consistency > model is. Has this been described somewhere? > > Thanks, > -n8 > > On Jul 13, 7:06 pm, Albert <albertpa...@gmail.com> wrote: > > > > > Hi! > > > This is a quick suggestion. > > > How about using a global counter (just like your title suggests). You > > can use a sharded global counter to facilitate your counting. > > > And use that counter as a "timestamp" / bookmark. > > > On every "event", you read from the global counter, use that value as > > your "timestamp", and then increment the global counter. > > > I'm not sure of it's implications, though. I'm not also sure if it > > actually guarantees uniqueness of "timestamps" when two events happen > > almost at the same time. > > > Perhaps you can get an idea from this. > > > Enjoy!- Hide quoted text - > > - Show quoted text - --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
