The example you describe will be strongly consistant in the high replication datastore. Take a look at the consistency section of the table on this page comparing master/slave with high replication: http://code.google.com/appengine/docs/python/datastore/hr/
You'll see there that gets, puts, and deletes are strongly consistant even with high replication. >From everything I've read about and experienced with regards to the high replication datastore, the only case where eventual consistency comes into play is with a query across entity groups. Each entity exists within its own entity group unless it has a parent, in which case it is grouped together in the same entity group as its parent. If you retrieve an entity from the datastore by its key, that will be strongly consistant because it only queries one entity group. -- -- Kyle Mulka Co-Founder, DealSavant http://www.dealsavant.com On Jul 10, 12:33 pm, bejayoharen <[email protected]> wrote: > I am designing an app that may not work well with the eventual > consistency model provided by the HR database, and thought someone > could provide some advice. Here is a typical situation: > > 1. Client A requests storage of data identified by KEY on GAE. > 2. the GAE app stores the data; and acknowledges the storage to Client > A. > 3. Client A tells Client B (via another communication protocol) to > fetch data identified by KEY. > 4. Client B asks GAE for the data identified by KEY. > > Unfortunately, with eventual consistency, step 4 may fail. Caching > won't help because 1. caching is not 100% reliable and 2. client A and > client B may be talking to different nodes with different caches. > Worse than this is a situation where instead of storing the data, > client A is updating and client B gets stale data. > > Is there some solution to this, or do I need to use the MS database? > If that's the case, I noticed that in some places, the MS database is > marked as "legacy", which has me worried. > > thanks > > bjorn -- You received this message because you are subscribed to the Google Groups "Google App Engine" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/google-appengine?hl=en.
