Convergent Replicated Data Types

Transcript

1. Convergent
   Replicated
   Data Types
   

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2. @vanstee
   vanstee@bignerdranch.com
   Patrick Van Stee
   

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3. “Structuring
   data so conflict
   resolution is
   automatic”
   

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4. Dynamo
   Trade consistency
   for availability and
   partition tolerance
   

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5. Node 1 Node 2
   { a: “200” } { a: “-3000” }
   :(
   

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6. Node 1 Node 2
   { a: “200” } { a: “-3000” }
   { a: “200”, a: “-3000” }
   Riak
   

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7. CRDT
   •Counter
   •Set
   •Graph
   •List
   •Tree
   

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8. CRDT
   •Counter
   •Set
   •Graph
   •List
   •Tree
   

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9. Counter
   •Can only be increased
   •Merge: use largest value
   

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10. Chat Room
    Karma
    Fault-Tolerant
    Distributed
    

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11. Serious Business
    { SB[PVS]: 0}
    Serious Coding
    { SB[PVS]: 1} # PVS++
    { SC[PVS]: 0}
    { SC[PVS]: 5} # PVS += 5
    { SB[PVS]: 2} # PVS++
    Merge
    { SB[PVS]: 2, SC[PVS]: 5} { SB[PVS]: 1, SC[PVS]: 5}
    { SB[PVS]: 2, SC[PVS]: 5}
    { PVS: 7}
    

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12. What about
    decrements?
    Use separate counters
    for positive and negative.
    Take the difference for
    the result.
    

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13. Serious Business
    { SB[PVS+]: 0, SB[PVS-]: 0 }
    Serious Coding
    { SB[PVS+]: 1, SB[PVS-]: 0 } # PVS++
    { SB[PVS+]: 0, SB[PVS-]: 0 }
    { SB[PVS+]: 5, SB[PVS-]: 0 } # PVS += 5
    { SB[PVS+]: 1, SB[PVS-]: 1 } # PVS--
    Merge
    { PVS+: 6, PVS-: 1 } { PVS+: 6, PVS-: 0 }
    { PVS+: 6, PVS-: 1 }
    { PVS: 5 }
    

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14. Set
    •Can only be added to
    •Merge: take the union
    

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15. Serious Business
    { PVS: [ ] }
    Serious Coding
    { PVS: [] } { PVS: [] }
    { PVS: [ ] }
    Merge
    { PVS: [ , ] }
    { PVS: [ , ] }
    { PVS: [ , , ] }
    { PVS: [ , , ] }
    

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16. Hold on, Can
    we remove
    stuff?
    Use separate sets for added
    and removed elements.
    

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17. Serious Business
    { PVS+: [ ], PVS-: [] }
    Serious Coding
    { PVS+: [], PVS-: [] } { PVS+: [], PVS-: [] }
    { PVS+: [ ], PVS-: [] }
    Merge
    { PVS+: [ , ], PVS-: [ ] }
    { PVS+: [ ], PVS-: [ ] }
    { PVS+: [ , ], PVS-: [] }
    { PVS+: [ , ], PVS-: [ ] }
    { PVS: [ ] }
    

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18. But wait,
    we can only
    remove once?
    

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19. U-Set
    •Append unique values
    to all set members
    •Garbage collection
    becomes an issue
    

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20. basho/riak_dt
    Demo
    

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21. Use Cases
    •Like button
    •Page Views
    •Shopping Cart
    

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22. Reference
    •INRIA paper
    •basho/riak_dt
    •RICON talk
    

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23. Beginning
    Ruby on Rails
    Course
    bignerdranch.com/classes/beginning_ruby_on_rails
    

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