| This gives a little more detail about each of the CRDT types: https://github.com/basho/riak/issues/354 Your assumptions are correct. Within Riak, an actor is a vnode, and counters behave as G-Counters. Keep in mind that Riak counters store both an increment and decrement for each actor, which allows decrements and negative counters as well while preserving the accuracy of G-Counters. Hope this helps, Jason
________________________________________________________________________ From: David Byron <dby...@dbyron.com> Date: Wed Oct 21 2015 15:03:04 GMT+1100 (AUS Eastern Summer Time) To: riak-users@lists.basho.com <riak-users@lists.basho.com> Subject: counter crdt in riak Apologies if this is basic question, or one that's already been answered. I've done a fair amount of digging (e.g. http://thread.gmane.org/gmane.comp.db.riak.user/12808/focus=12816), but
I'm still confused about the documentation regarding conflict resolution
for riak's crdt counter. Specifically this: https://github.com/basho/basho_docs/blame/riak/2.1.1/source/languages/en/riak/theory/concepts/crdts.md#L238
(using the blame view to get a line number reference in markdown), which
says: "Counters | Each actor keeps an independent count for increments and decrements; upon merge, the pairwise maximum of the counts for each actor will win (e.g. if one count for an actor holds 172 and the other
holds 173, 173 will win upon merge)" This makes it sound to me like an increment from one of the actors gets
dropped. Fingers crossed this isn't actually what happens. I think this is saying the same thing that the cdrt paper (section 3.1.2
State-based increment-only Counter (G-Counter) of https://hal.inria.fr/file/index/docid/555588/filename/techreport.pdf)
says -- that increments that happen during a partition eventually resolve correctly. I could use a more step-by-step illustration though
-- pairwise maximum of the counts for each actor is a little dense. Apologies for ugly formatting, but an example like this would make more
sense to me. - actor a increments counter a {a: 1} b {} - actor b increments counter a {a: 1} b {b: 1} - a merges b's info a {a: 1, b: 1} b {b: 1} - b merges a's info a:{a: 1, b: 1} b {a: 1, b: 1} so eventually this all resolves such that a and b both increment the counter by 2, right? Is this how riak's crdt counter works? If so I'll
breathe a sigh of relief and make a pull request against the docs if you
like. Thanks much for your help. -DB _______________________________________________ riak-users mailing list |
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