Thanks for the input. Transactions is exactly what I was looking for. I coding a small game where people can attack each other and decrease their hp. If players ended up quering for the players hp and different datastores contain different values, well that's not a good thing haha. I'm planning on using the memcache to store the players hp, but when the value is removed from the cache I got to get the newest value back into the memcache.
On Thu, Mar 3, 2011 at 11:28 AM, Ikai Lan (Google) <ika...@google.com> wrote: > Yes. The only way to correctly do this is with transactions and sharded > counters. > The better question, however, is this: what are you doing? Perhaps there is > an alternative solution. > > Ikai Lan > Developer Programs Engineer, Google App Engine > Blog: http://googleappengine.blogspot.com > Twitter: http://twitter.com/app_engine > Reddit: http://www.reddit.com/r/appengine > > > On Thu, Mar 3, 2011 at 10:57 AM, justin <thekeyboard...@gmail.com> wrote: >> >> I need to write code so that a user has a counter. This counter can be >> read, increase, and decrease. This counter is mission critical so I >> will use the high replication datastore. >> >> So lets say I create a counter entity which has a user entity as the >> ancestor. I increase the counter value and store the value. Almost >> simultaneously I get another request to read the counter. I get the >> entity from the datastore , using the correct ancestor chain, and I >> read the value. Is it possible that these two values will be >> different? If so, is there anyway way to prevent this from happening? >> >> -- >> You received this message because you are subscribed to the Google Groups >> "Google App Engine for Java" group. >> To post to this group, send email to >> google-appengine-java@googlegroups.com. >> To unsubscribe from this group, send email to >> google-appengine-java+unsubscr...@googlegroups.com. >> For more options, visit this group at >> http://groups.google.com/group/google-appengine-java?hl=en. >> > > -- > You received this message because you are subscribed to the Google Groups > "Google App Engine for Java" group. > To post to this group, send email to google-appengine-java@googlegroups.com. > To unsubscribe from this group, send email to > google-appengine-java+unsubscr...@googlegroups.com. > For more options, visit this group at > http://groups.google.com/group/google-appengine-java?hl=en. > -- You received this message because you are subscribed to the Google Groups "Google App Engine for Java" group. To post to this group, send email to google-appengine-java@googlegroups.com. To unsubscribe from this group, send email to google-appengine-java+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/google-appengine-java?hl=en.
