Val, PRIMARY_SYNC doesn't work correctly with the most common case of SQL query execution over REPLICATED cache. Also it has weird consequences for continuous queries when coupled with another performance-over-correctness property "readFromBackup=true": user may receive CQ notification with new value, but subsequent GET on local node may return old value.
On Tue, Apr 18, 2017 at 10:42 AM, Valentin Kulichenko < valentin.kuliche...@gmail.com> wrote: > This sounds more like an issue with query execution, rather than wrong > PRIMARY_SYNC > behavior. We already had a discussion about this optimization in replicated > cache and decided to switch it off by default. > > -Val > > On Tue, Apr 18, 2017 at 9:35 AM, Sergi Vladykin <sergi.vlady...@gmail.com> > wrote: > > > With replicated cache we can execute a query against backup partitions > that > > were not updated yet because of PRIMARY_SYNC. Thus we do not see an > update. > > > > Sergi > > > > 2017-04-18 10:30 GMT+03:00 Dmitriy Setrakyan <dsetrak...@apache.org>: > > > > > Vladimir, > > > > > > What is wrong with a query in PRIMARY_SYNC mode? Why won't it work? > > > > > > D. > > > > > > On Tue, Apr 18, 2017 at 12:25 AM, Vladimir Ozerov < > voze...@gridgain.com> > > > wrote: > > > > > > > Folks, > > > > > > > > I received a number of complaints from users that our default setting > > > favor > > > > performance at the cost of correctness and subtle behavior. > Yesterday I > > > > faced one such situation on my own. > > > > > > > > I started REPLICATED cache on several nodes, put some data, executed > > > simple > > > > SQL and got wrong result. No errors, no warnings. The problem was > > caused > > > by > > > > default PRIMARY_SYNC mode. WTF, our cache doesn't work out of the > box! > > > > > > > > Another widely known examples are data streamer behavior, "read form > > > > backups" + continuous queries. > > > > > > > > I propose to change our defaults to favor *correctness* over > > performance, > > > > and create good documentation and JavaDocs to explain users how to > tune > > > our > > > > product. Proposed changes: > > > > > > > > 1) FULL_SYNC as default; > > > > 2) "readFromBackups=false" as default; > > > > 3) "IgniteDataStreamer.allowOverwrite=true" as default. > > > > > > > > Users should not think how to make Ignite work correctly. It should > be > > > > correct out of the box. > > > > > > > > Vladimir. > > > > > > > > > >
