Hello, High Replication DS solves the issue of latency between requested get/put/delete operation and its actual completion,
but it still has limitations on how many put requests you can do per second - currently only 1 guaranteed write per second per entity group. (here at the bottom : http://code.google.com/appengine/docs/python/datastore/hr/overview.html) any entity may be considered as single-item entity group, so this applied to series of puts to the same entity. As I understand from your example, particular user are supposed to write into the same entity instance several times - so this may be potentially 'Contention Error' I have encountered such situation on frequently updated entity groups May be you may consider several shards for Email entity? Then , you may examine update times and sum chunks in proper order (provided you have some field mtime = db.DateTimeProperty(auto_now=True)) Or even better - collect some intermediate results in memcache instance and,say, every 1 or 2 seconds do actual write into datastore? Best regards, Den On Feb 25, 11:43 am, de Witte <[email protected]> wrote: > Hello, > > We are developing the following datastore for a big application. > > One table with 10.000.000 records. > > The application has at any given time 40.000 active users. > These users make frequently adjustments to these records. > In rare cases, more than one user writes to a single record. > > What happens if a specific user does four requests in a row to adjust a > single record. > > For example: > > Entity Email with property content; > > Request 1: get Email, add 'hello' to content, put Email. > Request 2: get Email, add ',how' to content, put Email. > Request 3: get Email, add ' are y' to content, put Email. > Request 4: get Email, add ' doing' to content, put Email. > > How can I ensure that the content property has the value 'hello, how are y > doing' after the fourth request? > > The entity group Email, has no parent. > > Is this scenario strongly consistent? -- 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.
