I thing HR-applications have more than one syncronised memcache - by me test save in HR-memcache in 3 times slower, than Master/Slave application.
On May 14, 6:56 pm, Sergey Schetinin <ser...@maluke.com> wrote: > So, I was watching the presentation on the HR datastore from the IO > 2011 (http://www.google.com/events/io/2011/sessions/more-9s-please-under-th... > ) and one thing caught my attention: the slides were showing the > frontend instances running in more than one datacenter at the same > time. So I understand that the memcached can lose data at any time and > if the app is migrated between the datacenters all of the data in the > cache are lost, however, running the app in two or more datacenters at > a time each DC having a separate memcached cluster, that changes the > properties quite significantly. > > For example let's consider an app that uses some memcached key to keep > a cursor where to write to the datastore, atomically incrementing it > after each write. Such an app can detect if such a key is not present > in the cache and determine what the cursor is by doing a query on the > database and then add it to the cache atomically. If we add the > possibility that there's another DC running the app w/ an independent > memcached instance, such an app would just corrupt its own data. > > I hope I explained my concern well enough, and I would love to hear an > answer from someone on the App Engine team. > > Thank you. > > -Sergey > > --http://self.maluke.com/ -- 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.
