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CRDT 101

CRDT 101

Sergey Arkhipov

December 09, 2014
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  1. 2009: CRDT ← CRDT CmRDT — Commutative Replicated Data Type

    Assuming causal delivery of updates and method termination, any op-based object that satisfies the commutativity property for all concurrent updates, and whose delivery precondition is satisfied by causal delivery, is strong eventual consistent.
  2. LWW-element-Set ← CRDT tweet = { id: "3b6730f1-50c7-4fad-ac47-ba8c2efadfc1", timestamp: 1416757099,

    user: "9seconds" message: "Test message" } def tweet_to_lww(tweet): return tweet["timestamp"], tweet
  3. LWW-element-Set ← CRDT A R A R (t1, a) (t1,

    a) (t2, b) (t3, c) (t2, b) (t2, b) (t4, c)
  4. LWW-element-Set ← CRDT A R A R (t1, a) (t1,

    a) (t2, b) (t3, c) (t2, b) (t2, b) (t4, c) (t4, c)
  5. LWW-element-Set ← CRDT A R A R (t1, a) (t1,

    a) (t2, b) (t3, c) (t2, b) (t2, b) (t4, c) (t4, c) Synchronizer (SoundCloud Roshi)
  6. LWW-element-Set ← CRDT A R (t1, a) (t1, a) (t3,

    c) (t2, b) (t2, b) (t4, c) (t4, c)
  7. LWW-element-Set ← CRDT A R A R (t1, a) (t1,

    a) (t2, b) (t3, c) (t2, b) (t4, c) (t4, c) Synchronizer (SoundCloud Roshi) (t3, c)
  8. Many CRDTs! ← CRDT ― Op-based Counter ― G-Counter ―

    State-based PN Counter ― LWW-Register ― MV-Register ― G-Set ― 2P-Set ― LWW-element-Set ― PN-Set ― OR Set ― Add-only monotonic DAG ― Add-Remove Partial Order data type ― RGA ― RHA ― TreeDoc ― Logoot ― WOOT ― WOOTH
  9. (Not) Many implementations ← CRDT ― Apache Cassandra ― Apache

    HBase ― Basho Riak ― SoundCloud Roshi ― Akka CRDT