Hi,
I got a rather simple question and I am sure there is a simple solution. Let's say I got a RPC endpoint that checks if an entity exists and then creates another entity. This RPC endpoint can be called simultaneously on different instances. Say we got a user object, and sometimes we generate an AccountStatus for the User. The generation is triggered by an RPC call that checks if AccountStatus for an User exists - if not it generates a new entity. The problem is: While one RPC checks if an entity exists - the other RPC call is already after the check (with no result) and generates the AccountStatus entity. This results in two entities being created and not one. I guess what I want to have is some kind of check and lock. My question is how to implement an "efficient" lock on a distributed environment like GAE. Transactions? Or better using memcache? Is there a best practise how to implement that? Thanks :) Best, Raphael -- 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.
