What you'd usually do is somewhere between 2) and 3) - namely, accept that siblings might occur (although rarely). Also, you'd have a resolution function with the property (besides being deterministic) that reconciliating two identical siblings would yield the same - i.e., f(X,X) = X. ________________________________________ Fra: riak-users-boun...@lists.basho.com [riak-users-boun...@lists.basho.com] På vegne af Justin Karneges [jus...@affinix.com] Sendt: 1. november 2011 21:34 Til: riak-users@lists.basho.com Emne: safely resolving conflicts on read
Hi, http://wiki.basho.com/Vector-Clocks.html contains this text: "It should be noted that if you are trying to resolve conflicts automatically, you can end up in a condition with which two clients are simultaneously resolving and creating new conflicts." If conflict resolution is moved to the reader, I'm curious what strategies people use to avoid this kind of feet stomping. Some ideas that have come to mind: 1) Have a deterministic way of deriving a correct/unified/winner value from multiple siblings, such that any reading client would always arrive at the same answer. Simply use this derived answer as the value read, but don't attempt to write a corrected value into Riak. The value could eventually be corrected at the time of a necessary write as opposed to a read reaction. 2) Determine a correct value per #1 above, but then attempt to write this value back into Riak in such a way that if multiple nodes were to write the same value simultaneously then they don't create siblings. I'm not sure if this is possible in Riak? 3) Determine a correct value per #1 above, and allow exactly one node to ever immediately write corrected values after a read. Something like "if hash(key) % node_count == current_node then do_correction". Since value correction is not vital to availability, there's no harm if the owning node is down. I just figure this would allow for self-healing over time. Maybe there are other ways. What do people really do? Thanks, Justin _______________________________________________ riak-users mailing list riak-users@lists.basho.com http://lists.basho.com/mailman/listinfo/riak-users_lists.basho.com _______________________________________________ riak-users mailing list riak-users@lists.basho.com http://lists.basho.com/mailman/listinfo/riak-users_lists.basho.com
