When n=3 in a three node cluster, sometimes two of those n are on the same node.
@siculars http://siculars.posterous.com Sent from my rotary phone. On Jan 5, 2012 11:07 AM, "Thomas Bakketun" <thomas.bakke...@copyleft.no> wrote: > Hello, > > Riak is based on eventual consistency concept, but sometimes it's > desirable to have absolute consistency. I though it would be possible to > implement this on top of Riak with the help of pr and wr parameters of > fetch and store, but when testing this I sometimes get worrying results. > > I have at test setup with Riak nodes in three virtual machines running > on my desktop machine. The test bucket has n_val=3 and allow_mult=true. > > On my desktop machine I constantly read from every node like this: > watch curl -v "'http://192.168.100.21:8098/riak/test/foo?pr=quorum'" > > When I pause two of the virtual machines, the remaining one starts to > fail with error message "PR-value unsatisfied: 1/2", just as expected. > But occasionally it will returns 200 OK for about 10 seconds, before it > starts returning "PR-value unsatisfied: 1/2". I can't predictably > reproduce this situation, but it's seems to happen when I resume a > machine that was paused when the other machines where running too. > > Pausing virtual machines to simulate downtime might be a bit > unrealistic. Still it concerns me that Riak can return stale data. Here > is an example: > > First I wrote a value when all nodes where up. Then I pause one of the > nodes and wrote a new value. Then I paused the two remaining nodes and > resume the first node. For a few seconds the first node then returned > 200 OK with the old value when though I supplied pr=quorum. > > I have also been able to do successful writes with w, dw and pw=quorum > with only one machine running. I thing the node also returned 200 OK > when the object was read with pr=quorum right after. > > The tests where done with Riak 1.0.0-1 running on Ubuntu 10.10 64 bit. > > -- > Thomas Bakketun, Senior software developer > T. +47 21 53 69 40 > Copyleft Solutions > www.copyleftsolutions.com > > > _______________________________________________ > 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
