Declarative, Distributed, Edge Computation

RICON 2015

Transcript

1. Declarative, Distributed, Edge Computation Christopher Meiklejohn // @cmeik RICON 2015, November 6th, 2015 1
2. RA RB
3. RA RB 1 set(1)
4. RA RB 1 set(1) 3 2 set(2) set(3)
5. RA RB 1 set(1) 3 2 set(2) set(3) ? ?
6. Synchronization • To enforce an order
 Makes programming easier 6
7. Synchronization • To enforce an order
 Makes programming easier • Eliminate accidental nondeterminism
 Prevent race conditions 6
8. Synchronization • To enforce an order
 Makes programming easier • Eliminate accidental nondeterminism
 Prevent race conditions • Techniques
 Locks, mutexes, semaphores, monitors, etc. 6
9. Difficult Cases • “Internet of Things”
 Low power, limited memory and connectivity 7
10. Difficult Cases • “Internet of Things”
 Low power, limited memory and connectivity • Mobile Gaming
 Offline operation with replicated, shared state 7
11. Zero Synchronization • We want to have our cake and eat it too. 8
12. Zero Synchronization • We want to have our cake and eat it too. • “Zero synchronization” as a starting point
 Add synchronization only where it is necessary 8
13. Zero Synchronization • We want to have our cake and eat it too. • “Zero synchronization” as a starting point
 Add synchronization only where it is necessary • Explore the limits
 Can we design a model of computation where it’s easy to write coordination-free computations that are free from concurrency anomalies? 8
14. 9 Strong Weak Strong (Data Center) Weak (Open Internet) Sharing (Application Property) Coupling (Infrastructure Property)
15. 9 Strong Weak Strong (Data Center) Weak (Open Internet) Sharing (Application Property) Coupling (Infrastructure Property) MapReduce SETI@Home
16. 9 Strong Weak Strong (Data Center) Weak (Open Internet) Sharing (Application Property) Coupling (Infrastructure Property) Twitter MapReduce SETI@Home
17. 9 Strong Weak Strong (Data Center) Weak (Open Internet) Sharing (Application Property) Coupling (Infrastructure Property) Twitter MapReduce SETI@Home Synchronization-Free Computations
18. The Fundamentals of Distributed Computation 10
19. Distributed Computation • Distributed to concurrent programming
 Consistency and now partial failure 11
20. Distributed Computation • Distributed to concurrent programming
 Consistency and now partial failure • Enforcing the “single system” illusion 11
21. Distributed Computation • Distributed to concurrent programming
 Consistency and now partial failure • Enforcing the “single system” illusion • Consistency model as a contract 11
22. Distributed Computation • Distributed to concurrent programming
 Consistency and now partial failure • Enforcing the “single system” illusion • Consistency model as a contract • Enforced through synchronization 11
23. Distributed Computation • Distributed to concurrent programming
 Consistency and now partial failure • Enforcing the “single system” illusion • Consistency model as a contract • Enforced through synchronization • Consistency model
 We can think of a consistency model as analogous to a programming paradigm 11
24. Why Is Synchronization Undesirable? 12
25. The Avatars of Time • The problem of time
 Handling physical time in applications is difficult 13
26. The Avatars of Time • The problem of time
 Handling physical time in applications is difficult • Time has three major avatars in computing 13
27. The Avatars of Time • The problem of time
 Handling physical time in applications is difficult • Time has three major avatars in computing • Mutable state in sequential systems 13
28. The Avatars of Time • The problem of time
 Handling physical time in applications is difficult • Time has three major avatars in computing • Mutable state in sequential systems • Nondeterminism in concurrent systems 13
29. The Avatars of Time • The problem of time
 Handling physical time in applications is difficult • Time has three major avatars in computing • Mutable state in sequential systems • Nondeterminism in concurrent systems ̣ Network latency in distributed systems 13
30. The Avatars of Time • The problem of time
 Handling physical time in applications is difficult • Time has three major avatars in computing • Mutable state in sequential systems • Nondeterminism in concurrent systems ̣ Network latency in distributed systems • Unavoidable
 Time is how users interact with programs 13
31. Parable of the Car • “Car driving on a highway” 14
32. Parable of the Car • “Car driving on a highway” • Friction needed for the car to grip the road 14
33. Parable of the Car • “Car driving on a highway” • Friction needed for the car to grip the road • Motors want as little friction as possible 14
34. Parable of the Car • “Car driving on a highway” • Friction needed for the car to grip the road • Motors want as little friction as possible • Time is like friction
 We can not completely eliminate friction, but aim to reduce it as much as possible 14
35. Physical Time (real world) Parable of the Car 15 • Time only at the interface
 The interface is a small part of the system, and this is where we introduction friction
36. Physical Time (real world) Parable of the Car 15 • Time only at the interface
 The interface is a small part of the system, and this is where we introduction friction • Physical time-free execution
 Internally, avoid synchronization as much as possible and virtualize notion of time
37. No Time In The Box? 16
38. No Time In The Box? 16 You program the box.
39. Weak Synchronization • Can we achieve anything without synchronization?
 Not really. 17
40. Weak Synchronization • Can we achieve anything without synchronization?
 Not really. • Strong Eventual Consistency (SEC)
 “Replicas that deliver the same updates have equivalent state” 17
41. Weak Synchronization • Can we achieve anything without synchronization?
 Not really. • Strong Eventual Consistency (SEC)
 “Replicas that deliver the same updates have equivalent state” • Primary requirement
 Eventual replica-to-replica communication 17
42. Weak Synchronization • Can we achieve anything without synchronization?
 Not really. • Strong Eventual Consistency (SEC)
 “Replicas that deliver the same updates have equivalent state” • Primary requirement
 Eventual replica-to-replica communication • Order insensitive! (Commutativity) 17
43. Weak Synchronization • Can we achieve anything without synchronization?
 Not really. • Strong Eventual Consistency (SEC)
 “Replicas that deliver the same updates have equivalent state” • Primary requirement
 Eventual replica-to-replica communication • Order insensitive! (Commutativity) • Duplicate insensitive! (Idempotent) 17
44. RA RB
45. RA RB 1 set(1)
46. RA RB 1 set(1) 3 2 set(2) set(3)
47. RA RB 1 3 2 3 3 set(1) set(2) set(3) max(2,3) max(2,3)
48. How can we succeed with Strong Eventual Consistency? 22
49. Programming SEC 1. Eliminate accidental nondeterminism
 (ex. deterministic, modeling non-monotonic operations monotonically) 23
50. Programming SEC 1. Eliminate accidental nondeterminism
 (ex. deterministic, modeling non-monotonic operations monotonically) 2. Retain the properties of functional programming
 (ex. confluence, referential transparency over composition) 23
51. Programming SEC 1. Eliminate accidental nondeterminism
 (ex. deterministic, modeling non-monotonic operations monotonically) 2. Retain the properties of functional programming
 (ex. confluence, referential transparency over composition) 3. Distributed, and fault-tolerant runtime
 (ex. replication) 23
52. Programming SEC 1. Eliminate accidental nondeterminism
 (ex. deterministic, modeling non-monotonic operations monotonically) 2. Retain the properties of functional programming
 (ex. confluence, referential transparency over composition) 3. Distributed, and fault-tolerant runtime
 (ex. replication) 24
53. Convergent Objects
 Conflict-Free 
 Replicated Data Types 25 SSS 2011
54. Conflict-Free 
 Replicated Data Types • Many types exist with different properties
 Sets, counters, registers, flags, maps, graphs 26
55. Conflict-Free 
 Replicated Data Types • Many types exist with different properties
 Sets, counters, registers, flags, maps, graphs • Strong Eventual Consistency
 Instances satisfy SEC property per-object 26
56. RA RB RC
57. RA RB RC {1} (1, {a}, {}) add(1)
58. RA RB RC {1} (1, {a}, {}) add(1) {1} (1, {c}, {}) add(1)
59. RA RB RC {1} (1, {a}, {}) add(1) {1} (1, {c}, {}) add(1) {} (1, {c}, {c}) remove(1)
60. RA RB RC {1} (1, {a}, {}) add(1) {1} (1, {c}, {}) add(1) {} (1, {c}, {c}) remove(1) {1} {1} {1} (1, {a, c}, {c}) (1, {a, c}, {c}) (1, {a, c}, {c})
61. Programming SEC 1. Eliminate accidental nondeterminism
 (ex. deterministic, modeling non-monotonic operations monotonically) 2. Retain the properties of functional programming
 (ex. confluence, referential transparency over composition) 3. Distributed, and fault-tolerant runtime
 (ex. replication) 32
62. Convergent Programs Lattice Processing 33 PPDP 2015
63. Lattice Processing (Lasp) • Distributed, deterministic dataflow
 Distributed, deterministic dataflow programming model for “eventually consistent” computations 34
64. Lattice Processing (Lasp) • Distributed, deterministic dataflow
 Distributed, deterministic dataflow programming model for “eventually consistent” computations • Convergent data structures
 Primary data abstraction is the CRDT 34
65. Lattice Processing (Lasp) • Distributed, deterministic dataflow
 Distributed, deterministic dataflow programming model for “eventually consistent” computations • Convergent data structures
 Primary data abstraction is the CRDT • Enables composition
 Provides functional composition of CRDTs that preserves the SEC property 34
66. 35 %% Create initial set. S1 = declare(set), %% Add elements to initial set and update. update(S1, {add, [1,2,3]}), %% Create second set. S2 = declare(set), %% Apply map operation between S1 and S2. map(S1, fun(X) -> X * 2 end, S2).
67. 36 %% Create initial set. S1 = declare(set), %% Add elements to initial set and update. update(S1, {add, [1,2,3]}), %% Create second set. S2 = declare(set), %% Apply map operation between S1 and S2. map(S1, fun(X) -> X * 2 end, S2).
68. 37 %% Create initial set. S1 = declare(set), %% Add elements to initial set and update. update(S1, {add, [1,2,3]}), %% Create second set. S2 = declare(set), %% Apply map operation between S1 and S2. map(S1, fun(X) -> X * 2 end, S2).
69. 38 %% Create initial set. S1 = declare(set), %% Add elements to initial set and update. update(S1, {add, [1,2,3]}), %% Create second set. S2 = declare(set), %% Apply map operation between S1 and S2. map(S1, fun(X) -> X * 2 end, S2).
70. 39 %% Create initial set. S1 = declare(set), %% Add elements to initial set and update. update(S1, {add, [1,2,3]}), %% Create second set. S2 = declare(set), %% Apply map operation between S1 and S2. map(S1, fun(X) -> X * 2 end, S2).
71. Lattice Processing (Lasp) • Functional and set-theoretic operations on sets
 Product, intersection, union, filter, map, fold 40
72. Lattice Processing (Lasp) • Functional and set-theoretic operations on sets
 Product, intersection, union, filter, map, fold • Metadata computation
 Performs transformation on the internal metadata of CRDTs allowing creation of “composed” CRDTs 40
73. Lasp Processes • Replicas as monotonic streams
 Each replica of a CRDT produces a monotonic stream of states 41
74. Lasp Processes • Replicas as monotonic streams
 Each replica of a CRDT produces a monotonic stream of states • Monotonic processes
 Read from one or more input replica streams and produce a single output replica stream 41
75. Lasp Processes • Replicas as monotonic streams
 Each replica of a CRDT produces a monotonic stream of states • Monotonic processes
 Read from one or more input replica streams and produce a single output replica stream • Inflationary reads
 Read operation ensures that we only read inflationary updates to replicas 41
76. Lattice Processing Monotonic Streams 42
77. RA {} C1 {} C2 {} 43
78. RA {} (1, {a}, {}) C1 (1, {a}, {}) {} C2 {} 44
79. RA {} (1, {a}, {}) (1, {a, c}, {}) C1 (1, {a}, {}) {} C2 (1, {c}, {}) {} 45
80. RA {} (1, {a}, {}) (1, {a, c}, {}) (1, {a, c}, {a}) C1 (1, {a}, {}) {} (1, {a}, {a}) C2 (1, {c}, {}) {} 46
81. RA {} (1, {a}, {}) (1, {a, c}, {}) (1, {a, c}, {a}) C1 (1, {a}, {}) {} (1, {a}, {a}) C2 (1, {c}, {}) {} (1, {a, c}, {a}) (1, {a, c}, {a}) (1, {a, c}, {a}) 47
82. RA {} (1, {a}, {}) (1, {a, c}, {}) (1, {a, c}, {a}) C1 (1, {a}, {}) {} (1, {a}, {a}) C2 (1, {c}, {}) {} (1, {a, c}, {a}) (1, {a, c}, {a}) (1, {a, c}, {a}) 48
83. Lattice Processing Monotonic Processes 49
84. RA {} P1 F(RA) {} 50
85. RA {} P1 F(RA) {} strict_read({}) 51
86. RA {} P1 F(RA) {} strict_read({}) (1, {a}, {}) 52
87. RA {} P1 F(RA) {} strict_read({}) (1, {a}, {}) F((1, {a}, {})) 53
88. RA {} P1 F(RA) {} strict_read({}) (1, {a}, {}) F((1, {a}, {})) (2, {a}, {}) 54
89. RA {} P1 F(RA) {} strict_read({}) (1, {a}, {}) F((1, {a}, {})) (2, {a}, {}) strict_read((1, {a}, {}) (1, {a}, {}) 55
90. RA {} P1 F(RA) {} strict_read({}) (1, {a}, {}) F((1, {a}, {})) (2, {a}, {}) strict_read((1, {a}, {}) (1, {a}, {}) (1, {a}, {a}) F((1, {a}, {a})) (2, {a}, {a}) strict_read((1, {a}, {a}) (1, {a}, {a}) 56
91. RA {} P1 F(RA) {} strict_read({}) (1, {a}, {}) (1, {a}, {}) (1, {a}, {a}) F((1, {a}, {a})) (2, {a}, {a}) strict_read((1, {a}, {a}) (1, {a}, {a}) 57
92. Programming SEC 1. Eliminate accidental nondeterminism
 (ex. deterministic, modeling non-monotonic operations monotonically) 2. Retain the properties of functional programming
 (ex. confluence, referential transparency over composition) 3. Distributed, and fault-tolerant runtime
 (ex. replication) 58
93. Distributed Runtime Selective Hearing 59 W-PSDS 2015
94. Selective Hearing • Epidemic broadcast based runtime system
 Provide a runtime system that can scale to large numbers of nodes, that is resilient to failures and provides efficient execution 60
95. Selective Hearing • Epidemic broadcast based runtime system
 Provide a runtime system that can scale to large numbers of nodes, that is resilient to failures and provides efficient execution • Well-matched to Lattice Processing (Lasp) 60
96. Selective Hearing • Epidemic broadcast based runtime system
 Provide a runtime system that can scale to large numbers of nodes, that is resilient to failures and provides efficient execution • Well-matched to Lattice Processing (Lasp) • Epidemic broadcast mechanisms provide weak ordering but are resilient and efficient 60
97. Selective Hearing • Epidemic broadcast based runtime system
 Provide a runtime system that can scale to large numbers of nodes, that is resilient to failures and provides efficient execution • Well-matched to Lattice Processing (Lasp) • Epidemic broadcast mechanisms provide weak ordering but are resilient and efficient • Lasp’s programming model is tolerant to message re-ordering, disconnections, and node failures 60
98. Selective Hearing • Epidemic broadcast based runtime system
 Provide a runtime system that can scale to large numbers of nodes, that is resilient to failures and provides efficient execution • Well-matched to Lattice Processing (Lasp) • Epidemic broadcast mechanisms provide weak ordering but are resilient and efficient • Lasp’s programming model is tolerant to message re-ordering, disconnections, and node failures • “Selective Receive”
 Nodes selectively receive and process messages based on interest 60
99. Programming SEC 1. Eliminate accidental nondeterminism
 (ex. deterministic, modeling non-monotonic operations monotonically) 2. Retain the properties of functional programming
 (ex. confluence, referential transparency over composition) 3. Distributed, and fault-tolerant runtime
 (ex. replication) 61
100. What can we build? Leaderboard 62
101. Leaderboard • Mobile game platform
 Local leaderboard tracking top-k highest scored games 63
102. Leaderboard • Mobile game platform
 Local leaderboard tracking top-k highest scored games • Clients will go offline
 Clients have limited connectivity and the system still needs to make progress while clients are offline 63
103. Client 1 Leaderboard Client 3 Leaderboard Client 2 Leaderboard Lasp Operation User-Maintained CRDT Lasp-Maintained CRDT 64
104. Leaderboard • Peer-to-peer dissemination
 Nodes periodically “merge” their state with a random peer 65
105. Leaderboard • Peer-to-peer dissemination
 Nodes periodically “merge” their state with a random peer • Complexity in the data type
 Each node tracks a top-k set of its own games in a bounded set 65
106. 66 %% Create a leaderboard datatype. L = declare({top_k, [2]}). %% Update leaderboard. update({set, Name, Score}, L).
107. 67 %% Create a leaderboard datatype. L = declare({top_k, [2]}). %% Update leaderboard. update({set, Name, Score}, L).
108. 68 %% Create a leaderboard datatype. L = declare({top_k, [2]}). %% Update leaderboard. update({set, Name, Score}, L).
109. What if we want to enhance the behavior? 69
110. What if we want to enhance the behavior? 69 Without the creation of a new datatype
111. What can we build? Per-User Leaderboard 70 EdgeCom 2016
112. Per-User Leaderboard • Enhance existing design
 Only the top score for each user at each device 71
113. Per-User Leaderboard • Enhance existing design
 Only the top score for each user at each device • Minimize transmitted state
 Prevent transmission of state that is not necessary to perform the computation 71
114. Per-User Leaderboard • Enhance existing design
 Only the top score for each user at each device • Minimize transmitted state
 Prevent transmission of state that is not necessary to perform the computation • Compose data types
 Build a per-user leaderboard through the composition of existing types 71
115. Client1 Scores Local Top-K Fold Global Top-K Lasp Operation Input User-Maintained CRDT Output Lasp-Maintained CRDT Fold Client3 Scores Local Top-K Fold Global Top-K Fold Client2 Scores Local Top-K Fold Global Top-K Fold 72
116. Client1 Scores Local Top-K Fold Global Top-K Fold 73 Client1 Scores Local Top-K Fold Global Top-K Fold Client3 Scores Local Top-K Fold Global Top-K Fold Client2 Scores Local Top-K Fold Global Top-K Fold
117. Client1 Scores Local Top-K Fold Global Top-K Fold 74 Client1 Scores Local Top-K Fold Global Top-K Fold Client3 Scores Local Top-K Fold Global Top-K Fold Client2 Scores Local Top-K Fold Global Top-K Fold
118. Client1 Scores Local Top-K Fold Global Top-K Fold 75 Client1 Scores Local Top-K Fold Global Top-K Fold Client3 Scores Local Top-K Fold Global Top-K Fold Client2 Scores Local Top-K Fold Global Top-K Fold
119. Client1 Scores Local Top-K Fold Global Top-K Fold 76 Client1 Scores Local Top-K Fold Global Top-K Fold Client3 Scores Local Top-K Fold Global Top-K Fold Client2 Scores Local Top-K Fold Global Top-K Fold
120. Client1 Scores Local Top-K Fold Global Top-K Fold 77 Client1 Scores Local Top-K Fold Global Top-K Fold Client3 Scores Local Top-K Fold Global Top-K Fold Client2 Scores Local Top-K Fold Global Top-K Fold
121. Client1 Scores Local Top-K Fold Global Top-K Fold 78 Client1 Scores Local Top-K Fold Global Top-K Fold Client3 Scores Local Top-K Fold Global Top-K Fold Client2 Scores Local Top-K Fold Global Top-K Fold
122. Client1 Scores Local Top-K Fold Global Top-K Lasp Operation Input User-Maintained CRDT Output Lasp-Maintained CRDT Fold Client3 Scores Local Top-K Fold Global Top-K Fold Client2 Scores Local Top-K Fold Global Top-K Fold 79 Client1 Scores Local Top-K Fold Global Top-K Fold Client3 Scores Local Top-K Fold Global Top-K Fold Client2 Scores Local Top-K Fold Global Top-K Fold
123. Per-User Leaderboard • Dynamically scoped variables
 Variable which take different values depending on where it is executing 80
124. Per-User Leaderboard • Dynamically scoped variables
 Variable which take different values depending on where it is executing • Dynamically scoped fold operation
 Perform a distributed “reduce” operation that combines the state of a dynamically scoped variables across 80
125. 81 %% Create a global leaderboard. G = declare({top_k, [10]}). %% Create a local leaderboard. L = declare_dynamic({top_k, [10]}). %% Create a set of scores. S = declare_dynamic(set). %% Compute local top-k list. fold(S, fun max_by_name/2, L). %% Compute global top-k list. fold_dynamic(L, fun max_by_name/2, G).
126. 82 %% Create a global leaderboard. G = declare({top_k, [10]}). %% Create a local leaderboard. L = declare_dynamic({top_k, [10]}). %% Create a set of scores. S = declare_dynamic(set). %% Compute local top-k list. fold(S, fun max_by_name/2, L). %% Compute global top-k list. fold_dynamic(L, fun max_by_name/2, G).
127. 83 %% Create a global leaderboard. G = declare({top_k, [10]}). %% Create a local leaderboard. L = declare_dynamic({top_k, [10]}). %% Create a set of scores. S = declare_dynamic(set). %% Compute local top-k list. fold(S, fun max_by_name/2, L). %% Compute global top-k list. fold_dynamic(L, fun max_by_name/2, G).
128. 84 %% Create a global leaderboard. G = declare({top_k, [10]}). %% Create a local leaderboard. L = declare_dynamic({top_k, [10]}). %% Create a set of scores. S = declare_dynamic(set). %% Compute local top-k list. fold(S, fun max_by_name/2, L). %% Compute global top-k list. fold_dynamic(L, fun max_by_name/2, G).
129. 85 %% Create a global leaderboard. G = declare({top_k, [10]}). %% Create a local leaderboard. L = declare_dynamic({top_k, [10]}). %% Create a set of scores. S = declare_dynamic(set). %% Compute local top-k list. fold(S, fun max_by_name/2, L). %% Compute global top-k list. fold_dynamic(L, fun max_by_name/2, G).
130. 86 %% Create a global leaderboard. G = declare({top_k, [10]}). %% Create a local leaderboard. L = declare_dynamic({top_k, [10]}). %% Create a set of scores. S = declare_dynamic(set). %% Compute local top-k list. fold(S, fun max_by_name/2, L). %% Compute global top-k list. fold_dynamic(L, fun max_by_name/2, G).
131. Let’s look at a larger application 87
132. Let’s look at a larger application 87 With visible 
 non-monotonicity
133. What can we build? Advertisement Counter 88
134. Advertisement Counter • Mobile game platform selling advertisement space
 Advertisements are paid according to a minimum number of impressions 89
135. Advertisement Counter • Mobile game platform selling advertisement space
 Advertisements are paid according to a minimum number of impressions • Clients will go offline
 Clients have limited connectivity and the system still needs to make progress while clients are offline 89
136. Ads Rovio Ad Counter 1 Rovio Ad Counter 2 Riot Ad Counter 1 Riot Ad Counter 2 Contracts Ads Contracts Ads With Contracts Riot Ads Rovio Ads Filter Product Read 50,000 Remove Increment Read Union Lasp Operation User-Maintained CRDT Lasp-Maintained CRDT Rovio Ad Counter 1 Rovio Ad Counter 2 Riot Ad Counter 1 Rovio Ad Counter 1 Rovio Ad Counter 2 Riot Ad Counter 1 Rovio Ad Counter 1 Rovio Ad Counter 2 Riot Ad Counter 1 Rovio Ad Counter 1 Rovio Ad Counter 2 Riot Ad Counter 1 Client Side, Single Copy at Client 90
137. Ads Rovio Ad Counter 1 Rovio Ad Counter 2 Riot Ad Counter 1 Riot Ad Counter 2 Contracts Ads Contracts Riot Ads Rovio Ads Product Read 50,000 Remove Increment Union 91 Ads Rovio Ad Counter 1 Rovio Ad Counter 2 Riot Ad Counter 1 Riot Ad Counter 2 Contracts Ads Contracts Ads With Contracts Riot Ads Rovio Ads Filter Product Read 50,000 Remove Increment Read Union Lasp Operation User-Maintained CRDT Lasp-Maintained CRDT Rovio Ad Counter 1 Rovio Ad Counter 2 Riot Ad Counter 1 Rovio Ad Counter 1 Rovio Ad Counter 2 Riot Ad Counter 1 Rovio Ad Counter 1 Rovio Ad Counter 2 Riot Ad Counter 1 Rovio Ad Counter 1 Rovio Ad Counter 2 Riot Ad Counter 1 Client Side, Single Copy at Client
138. Ads Rovio Ad Counter 1 Rovio Ad Counter 2 Riot Ad Counter 1 Riot Ad Counter 2 Contracts Ads Contracts Ads With Contracts Riot Ads Rovio Ads Filter Product Read 50,000 Remove Increment Read Union Rovio Ad Counter 1 Rovio Ad Counter 1 Rovio Ad Counter 1 Rovio Ad Counter 1 Client 92 Ads Rovio Ad Counter 1 Rovio Ad Counter 2 Riot Ad Counter 1 Riot Ad Counter 2 Contracts Ads Contracts Ads With Contracts Riot Ads Rovio Ads Filter Product Read 50,000 Remove Increment Read Union Lasp Operation User-Maintained CRDT Lasp-Maintained CRDT Rovio Ad Counter 1 Rovio Ad Counter 2 Riot Ad Counter 1 Rovio Ad Counter 1 Rovio Ad Counter 2 Riot Ad Counter 1 Rovio Ad Counter 1 Rovio Ad Counter 2 Riot Ad Counter 1 Rovio Ad Counter 1 Rovio Ad Counter 2 Riot Ad Counter 1 Client Side, Single Copy at Client
139. Ads ovio Ad ounter 1 ovio Ad ounter 2 iot Ad ounter 1 iot Ad ounter 2 Contracts Ads Contracts Ads With Contracts Riot Ads Rovio Ads Filter Product Read 50,000 Remove Increment Read Union Rovio Ad Counter 1 Ro C Rovio Ad Counter 1 Ro C Rovio Ad Counter 1 Ro C Rovio Ad Counter 1 Ro C Client Side, Sing 93 Ads Rovio Ad Counter 1 Rovio Ad Counter 2 Riot Ad Counter 1 Riot Ad Counter 2 Contracts Ads Contracts Ads With Contracts Riot Ads Rovio Ads Filter Product Read 50,000 Remove Increment Read Union Lasp Operation User-Maintained CRDT Lasp-Maintained CRDT Rovio Ad Counter 1 Rovio Ad Counter 2 Riot Ad Counter 1 Rovio Ad Counter 1 Rovio Ad Counter 2 Riot Ad Counter 1 Rovio Ad Counter 1 Rovio Ad Counter 2 Riot Ad Counter 1 Rovio Ad Counter 1 Rovio Ad Counter 2 Riot Ad Counter 1 Client Side, Single Copy at Client
140. Ads Contracts Ads Contracts Ads With Contracts Riot Ads Rovio Ads Filter Product move Read Union Rovio Ad Counter 1 Rovio Ad Counter 2 Riot Ad Counter 1 Rovio Ad Counter 1 Rovio Ad Counter 2 Riot Ad Counter 1 Rovio Ad Counter 1 Rovio Ad Counter 2 Riot Ad Counter 1 Rovio Ad Counter 1 Rovio Ad Counter 2 Riot Ad Counter 1 Client Side, Single Copy at Client 94 Ads Rovio Ad Counter 1 Rovio Ad Counter 2 Riot Ad Counter 1 Riot Ad Counter 2 Contracts Ads Contracts Ads With Contracts Riot Ads Rovio Ads Filter Product Read 50,000 Remove Increment Read Union Lasp Operation User-Maintained CRDT Lasp-Maintained CRDT Rovio Ad Counter 1 Rovio Ad Counter 2 Riot Ad Counter 1 Rovio Ad Counter 1 Rovio Ad Counter 2 Riot Ad Counter 1 Rovio Ad Counter 1 Rovio Ad Counter 2 Riot Ad Counter 1 Rovio Ad Counter 1 Rovio Ad Counter 2 Riot Ad Counter 1 Client Side, Single Copy at Client
141. Ads Contracts Ads Contracts Ads With Contracts Filter Product Read Union Rovio Ad Counter 1 Rovio Ad Counter 2 Riot Ad Counter 1 Rovio Ad Counter 1 Rovio Ad Counter 2 Riot Ad Counter 1 Rovio Ad Counter 1 Rovio Ad Counter 2 Riot Ad Counter 1 Rovio Ad Counter 1 Rovio Ad Counter 2 Riot Ad Counter 1 Client Side, Single Copy at Client 95 Ads Rovio Ad Counter 1 Rovio Ad Counter 2 Riot Ad Counter 1 Riot Ad Counter 2 Contracts Ads Contracts Ads With Contracts Riot Ads Rovio Ads Filter Product Read 50,000 Remove Increment Read Union Lasp Operation User-Maintained CRDT Lasp-Maintained CRDT Rovio Ad Counter 1 Rovio Ad Counter 2 Riot Ad Counter 1 Rovio Ad Counter 1 Rovio Ad Counter 2 Riot Ad Counter 1 Rovio Ad Counter 1 Rovio Ad Counter 2 Riot Ad Counter 1 Rovio Ad Counter 1 Rovio Ad Counter 2 Riot Ad Counter 1 Client Side, Single Copy at Client
142. Ads Rovio Ad Counter 1 Rovio Ad Counter 2 Riot Ad Counter 1 Riot Ad Counter 2 Contracts Ads Contracts Ads With Contracts Riot Ads Rovio Ads Filter Product Read 50,000 Remove Increment Read Union Rovio Ad Counter 1 Rovio Ad Counter 2 Riot Ad Counter 1 Rovio Ad Counter 1 Rovio Ad Counter 2 Riot Ad Counter 1 Rovio Ad Counter 1 Rovio Ad Counter 2 Riot Ad Counter 1 Rovio Ad Counter 1 Rovio Ad Counter 2 Riot Ad Counter 1 Client Side, Single Copy at Client 96 Ads Rovio Ad Counter 1 Rovio Ad Counter 2 Riot Ad Counter 1 Riot Ad Counter 2 Contracts Ads Contracts Ads With Contracts Riot Ads Rovio Ads Filter Product Read 50,000 Remove Increment Read Union Lasp Operation User-Maintained CRDT Lasp-Maintained CRDT Rovio Ad Counter 1 Rovio Ad Counter 2 Riot Ad Counter 1 Rovio Ad Counter 1 Rovio Ad Counter 2 Riot Ad Counter 1 Rovio Ad Counter 1 Rovio Ad Counter 2 Riot Ad Counter 1 Rovio Ad Counter 1 Rovio Ad Counter 2 Riot Ad Counter 1 Client Side, Single Copy at Client
143. Ads Rovio Ad Counter 1 Rovio Ad Counter 2 Riot Ad Counter 1 Riot Ad Counter 2 Contracts Ads Contracts Riot Ads Rovio Ads Fil Product Read 50,000 Remove Increment Union 97 Ads Rovio Ad Counter 1 Rovio Ad Counter 2 Riot Ad Counter 1 Riot Ad Counter 2 Contracts Ads Contracts Ads With Contracts Riot Ads Rovio Ads Filter Product Read 50,000 Remove Increment Read Union Lasp Operation User-Maintained CRDT Lasp-Maintained CRDT Rovio Ad Counter 1 Rovio Ad Counter 2 Riot Ad Counter 1 Rovio Ad Counter 1 Rovio Ad Counter 2 Riot Ad Counter 1 Rovio Ad Counter 1 Rovio Ad Counter 2 Riot Ad Counter 1 Rovio Ad Counter 1 Rovio Ad Counter 2 Riot Ad Counter 1 Client Side, Single Copy at Client
144. Ads Rovio Ad Counter 1 Rovio Ad Counter 2 Riot Ad Counter 1 Riot Ad Counter 2 Contracts Ads Contracts Ads With Contracts Riot Ads Rovio Ads Filter Product Read 50,000 Remove Increment Read Union Rovio Ad Counter 1 Rovio Ad Counter 2 Riot Ad Counter 1 Rovio Ad Counter 1 Rovio Ad Counter 2 Riot Ad Counter 1 Rovio Ad Counter 1 Rovio Ad Counter 2 Riot Ad Counter 1 Rovio Ad Counter 1 Rovio Ad Counter 2 Riot Ad Counter 1 Client Side, Single Copy at Client 98 Ads Rovio Ad Counter 1 Rovio Ad Counter 2 Riot Ad Counter 1 Riot Ad Counter 2 Contracts Ads Contracts Ads With Contracts Riot Ads Rovio Ads Filter Product Read 50,000 Remove Increment Read Union Lasp Operation User-Maintained CRDT Lasp-Maintained CRDT Rovio Ad Counter 1 Rovio Ad Counter 2 Riot Ad Counter 1 Rovio Ad Counter 1 Rovio Ad Counter 2 Riot Ad Counter 1 Rovio Ad Counter 1 Rovio Ad Counter 2 Riot Ad Counter 1 Rovio Ad Counter 1 Rovio Ad Counter 2 Riot Ad Counter 1 Client Side, Single Copy at Client
145. Advertisement Counter • Completely monotonic
 Disabling advertisements and contracts are all modeled through monotonic state growth 99
146. Advertisement Counter • Completely monotonic
 Disabling advertisements and contracts are all modeled through monotonic state growth • Arbitrary distribution
 Use of convergent data structures allows computational graph to be arbitrarily distributed 99
147. Advertisement Counter • Completely monotonic
 Disabling advertisements and contracts are all modeled through monotonic state growth • Arbitrary distribution
 Use of convergent data structures allows computational graph to be arbitrarily distributed • Divergence
 Divergence is a factor of synchronization period 99
148. 100 %% Generate a series of contracts. Contracts = declare(set), %% Generate advertisements. RiotAds = declare(set), RovioAds = declare(set), create_advertisements_and_contracts(RiotAds, Contracts), create_advertisements_and_contracts(RovioAds, Contracts), %% Union ads. Ads = declare(set), union(RovioAds, RiotAds, Ads), %% Compute the product of both ads and contracts. AdsContracts = declare(set), product(Ads, Contracts, AdsContracts), %% Filter items by join on item it. AdsWithContracts = declare(set), FilterFun = fun({#ad{id=Id1}, #contract{id=Id2}}) -> Id1 =:= Id2 end, filter(AdsContracts, FilterFun, AdsWithContracts).
149. 101 %% Generate a series of contracts. Contracts = declare(set), %% Generate advertisements. RiotAds = declare(set), RovioAds = declare(set), create_advertisements_and_contracts(RiotAds, Contracts), create_advertisements_and_contracts(RovioAds, Contracts), %% Union ads. Ads = declare(set), union(RovioAds, RiotAds, Ads), %% Compute the product of both ads and contracts. AdsContracts = declare(set), product(Ads, Contracts, AdsContracts), %% Filter items by join on item it. AdsWithContracts = declare(set), FilterFun = fun({#ad{id=Id1}, #contract{id=Id2}}) -> Id1 =:= Id2 end, filter(AdsContracts, FilterFun, AdsWithContracts).
150. 102 %% Generate a series of contracts. Contracts = declare(set), %% Generate advertisements. RiotAds = declare(set), RovioAds = declare(set), create_advertisements_and_contracts(RiotAds, Contracts), create_advertisements_and_contracts(RovioAds, Contracts), %% Union ads. Ads = declare(set), union(RovioAds, RiotAds, Ads), %% Compute the product of both ads and contracts. AdsContracts = declare(set), product(Ads, Contracts, AdsContracts), %% Filter items by join on item it. AdsWithContracts = declare(set), FilterFun = fun({#ad{id=Id1}, #contract{id=Id2}}) -> Id1 =:= Id2 end, filter(AdsContracts, FilterFun, AdsWithContracts).
151. 103 %% Generate a series of contracts. Contracts = declare(set), %% Generate advertisements. RiotAds = declare(set), RovioAds = declare(set), create_advertisements_and_contracts(RiotAds, Contracts), create_advertisements_and_contracts(RovioAds, Contracts), %% Union ads. Ads = declare(set), union(RovioAds, RiotAds, Ads), %% Compute the product of both ads and contracts. AdsContracts = declare(set), product(Ads, Contracts, AdsContracts), %% Filter items by join on item it. AdsWithContracts = declare(set), FilterFun = fun({#ad{id=Id1}, #contract{id=Id2}}) -> Id1 =:= Id2 end, filter(AdsContracts, FilterFun, AdsWithContracts).
152. 104 %% Generate a series of contracts. Contracts = declare(set), %% Generate advertisements. RiotAds = declare(set), RovioAds = declare(set), create_advertisements_and_contracts(RiotAds, Contracts), create_advertisements_and_contracts(RovioAds, Contracts), %% Union ads. Ads = declare(set), union(RovioAds, RiotAds, Ads), %% Compute the product of both ads and contracts. AdsContracts = declare(set), product(Ads, Contracts, AdsContracts), %% Filter items by join on item it. AdsWithContracts = declare(set), FilterFun = fun({#ad{id=Id1}, #contract{id=Id2}}) -> Id1 =:= Id2 end, filter(AdsContracts, FilterFun, AdsWithContracts).
153. 105 %% Generate a series of contracts. Contracts = declare(set), %% Generate advertisements. RiotAds = declare(set), RovioAds = declare(set), create_advertisements_and_contracts(RiotAds, Contracts), create_advertisements_and_contracts(RovioAds, Contracts), %% Union ads. Ads = declare(set), union(RovioAds, RiotAds, Ads), %% Compute the product of both ads and contracts. AdsContracts = declare(set), product(Ads, Contracts, AdsContracts), %% Filter items by join on item it. AdsWithContracts = declare(set), FilterFun = fun({#ad{id=Id1}, #contract{id=Id2}}) -> Id1 =:= Id2 end, filter(AdsContracts, FilterFun, AdsWithContracts).
154. Client3 Lasp Operation User-Maintained CRDT Lasp-Maintained CRDT Riot Ad Counter 1 Client1 Client2 Rovio Ad Counter 1 Rovio Ad Counter 2 Rovio Ad Counter 1 Rovio Ad Counter 2 Rovio Ad Counter 1 Riot Ad Counter 2 Riot Ad Counter 1 Riot Ad Counter 1 Ads With Contracts Ads With Contracts Ads With Contracts Server Ads With Contracts Server Computation! 106
155. Client3 Lasp Operation User-Maintained CRDT Lasp-Maintained CRDT Riot Ad Counter 1 Client1 Client2 Rovio Ad Counter 1 Rovio Ad Counter 2 Rovio Ad Counter 1 Rovio Ad Counter 2 Rovio Ad Counter 1 Riot Ad Counter 2 Riot Ad Counter 1 Riot Ad Counter 1 Ads With Contracts Ads With Contracts Ads With Contracts Server Ads With Contracts Server Computation! 107
156. Client3 Lasp Operation User-Maintained CRDT Lasp-Maintained CRDT Riot Ad Counter 1 Client1 Client2 Rovio Ad Counter 1 Rovio Ad Counter 2 Rovio Ad Counter 1 Rovio Ad Counter 2 Rovio Ad Counter 1 Riot Ad Counter 2 Riot Ad Counter 1 Riot Ad Counter 1 Ads With Contracts Ads With Contracts Ads With Contracts Server Ads With Contracts Server Computation! 108
157. Advertisement Counter • “Servers” as peers to “clients”
 Servers are peers to clients that perform additional computation 109
158. Advertisement Counter • “Servers” as peers to “clients”
 Servers are peers to clients that perform additional computation • Any node can disable an advertisement under this model given enough information 109
159. Advertisement Counter • “Servers” as peers to “clients”
 Servers are peers to clients that perform additional computation • Any node can disable an advertisement under this model given enough information • “Servers” as trusted nodes
 Serve as a location for performing “exactly once” side- effects 109
160. Advertisement Counter • “Servers” as peers to “clients”
 Servers are peers to clients that perform additional computation • Any node can disable an advertisement under this model given enough information • “Servers” as trusted nodes
 Serve as a location for performing “exactly once” side- effects • Billing customers must be done at a central point by a trusted node in the system 109
161. We’ve build up from zero synchronization 110
162. We’ve build up from zero synchronization 110 Instead of working to remove synchronization
163. What have we learned? 111
164. Key Points • Synchronization is expensive
 Locking and other synchronization mechanisms limit scalability to the critical section 112
165. Key Points • Synchronization is expensive
 Locking and other synchronization mechanisms limit scalability to the critical section • Synchronization is sometimes not possible
 Mobile and “Internet of Things” applications make synchronization for replicated state impractical 112
166. Key Points • Synchronization is expensive
 Locking and other synchronization mechanisms limit scalability to the critical section • Synchronization is sometimes not possible
 Mobile and “Internet of Things” applications make synchronization for replicated state impractical • Apply synchronization only where required
 Global invariants, atomic visibility, etc. 112
167. How do I learn more? 113
168. Publications • “Lasp: A Language for Distributed, Coordination-Free Programming” 
 ACM SIGPLAN PPDP 2015 • “Selective Hearing: An Approach to Distributed, Eventually Consistent Edge Computation”
 IEEE W-PSDS 2015 • “The Implementation and Use of a Generic Dataflow Behaviour in Erlang”
 ACM SIGPLAN Erlang Workshop ’15 • “Lasp: A Language for Distributed, Eventually Consistent Computations with CRDTs"
 PaPoC 2015 • “Declarative, Sliding Window Aggregations for Computations at the Edge"
 IEEE EdgeCom 2016 114
169. SyncFree is a European research project taking place for 3 years, staring October 2013, and is funded by the European Union, grant agreement n° 609551. 115
170. Thanks! 116 Christopher Meiklejohn @cmeik