Dunno about production, but the developer mode takes issue with it. Even a simple single-entity transaction commit fails in M/S mode with the test harness - ie, without calling this method:
LocalDatastoreServiceTestConfig.setDefaultHighRepJobPolicyUnappliedJobPercentage(100) commit() always produces this: java.lang.IllegalArgumentException: transactions on multiple entity groups only allowed in High Replication applications :-( Jeff On Tue, Oct 18, 2011 at 1:44 PM, Alfred Fuller <arfuller+appeng...@google.com> wrote: > I believe (you should test this) that it won't do any harm to set XG=true in > master slave (it will just ignore you). > > On Tue, Oct 18, 2011 at 1:28 PM, Jeff Schnitzer <j...@infohazard.org> wrote: >> >> On Tue, Oct 18, 2011 at 9:07 AM, David Gay (Google) <d...@google.com> >> wrote: >> > >> > One other consideration: XG transactions do not work on master/slave. >> > While the default could be different depending on whether HRD is used, >> > that definitely has drawbacks. >> >> How can I detect if running on HRD vs M/S? I don't see anything on >> SystemProperty. I could try starting an XG transaction and catching >> the exception, but that would add an extra RPC to every Objectify >> app's startup time :-( >> >> The XG issue seems pretty easily solved by documentation: >> >> 1) If you're running on M/S, you can only use one entity group in a txn. >> 2) If you're running on HRD, you can use up to 5 entity groups in a txn. >> 2a) If you use multiple entity groups in a txn, this is implemented >> with 2pc and may produce surprising effects like >> ConcurrentModificationException on read. This doesn't really matter >> in practice if you use the RepeatInTransaction pattern. >> >> Put it this way: Non-ancestor queries work funky on the HRD too. Yet >> I don't need to set a special flag just to issue non-ancestor queries. >> Understanding eventual consistency and exotic transaction behavior is >> just part of working with GAE. Magic flags that enable otherwise >> expected behavior don't really help. >> >> Jeff >> >> -- >> 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.
