F# in social gaming (CodeMash 15)

1. F# in Social GamingF# in Social Gaming Yan Cui (@theburningmonk)

2. agenda

3. Hi, my name is Yan Cui.

5. 1MILLION USERS ACTIVE DAILY

6. 250MILLION DAY PER REQUEST

7. why F#?

8. time to market

9. correctness

10. efficient

11. tame complexity

12. Implementing a slots engine

13. Collectables Wager Size Special Symbol Avg Wager Size Web Server call

14. • Line Win! – X number of matching symbols on adjacent columns! – Positions have to be a ‘line’! – Wild symbols substitute for other symbols! ! • Scatter Win! – X number of matching symbols anywhere! – Triggers bonus game

15. What symbols should land?! Any special symbol wins?! Did the player win anything?

16. What the player’s new average wager?

17. Should the player receive collectables?

18. type Symbol = Standard! of string! ! ! ! | Wild

19. type Symbol = Standard! of string! ! ! ! | Wild e.g.! Standard “hat”! ! Standard “shoe”! ! Standard “bonus”! ! …

20. type Symbol = Standard! of string! ! ! ! | Wild i.e.! Wild

21. ! ! ! type Win = LineWin of int * Symbol * int! ! | ScatterWin of Symbol * int

22. ! ! ! type Win = LineWin of int * Symbol * int! ! | ScatterWin of Symbol * int e.g.! LineWin (5, Standard “shoe”, 4)

23. ! ! ! type Win = LineWin of int * Symbol * int! ! | ScatterWin of Symbol * int e.g.! ScatterWin (Standard “bonus”, 3)

24. type LineNum = int! type Count! = int! ! type Win = LineWin of LineNum * Symbol * Count! ! | ScatterWin of Symbol * Count

25. type LineNum = int! type Count! = int! ! type Win = LineWin of LineNum * Symbol * Count! ! | ScatterWin of Symbol * Count e.g.! LineWin (5, Standard “shoe”, 4)

26. type LineNum = int! type Count! = int! ! type Win = LineWin of LineNum * Symbol * Count! ! | ScatterWin of Symbol * Count e.g.! ScatterWin (Standard “bonus”, 3)

27. make invalid states unrepresentable

28. NASA orbiter crashed because one engineer accidentally used miles instead of kilometres

29. you’re never too smart to make mistakes

30. [<Measure>]! type Pence e.g.! 42<Pence>! ! 153<Pence>! ! …

31. 10<Meter> / 2<Second> ! = 5<Meter/Second>! 10<Meter> * 2<Second> ! = 20<Meter Second> ! 10<Meter> + 10<Meter> ! = 20<Meter>! 10<Meter> * 10! ! ! = 100<Meter>! 10<Meter> * 10<Meter> ! = 100<Meter2>! 10<Meter> + 2<Second> ! // error! 10<Meter> + 2 ! ! ! // error

32. 10<Meter> / 2<Second> ! = 5<Meter/Second>! 10<Meter> * 2<Second> ! = 20<Meter Second> ! 10<Meter> + 10<Meter> ! = 20<Meter>! 10<Meter> * 10! ! ! = 100<Meter>! 10<Meter> * 10<Meter> ! = 100<Meter2>! 10<Meter> + 2<Second> ! // error! 10<Meter> + 2 ! ! ! // error

33. type Wager = int64<Pence>! type Multiplier = int! ! type Payout = Coins! of Wager! ! ! | MultipliedCoins of Multiplier * Wager! ! ! | Multi! of Payout list! ! ! | BonusGame

36. type State = ! {! AvgWager! : Wager! SpecialSymbol : Symbol! Collectables : Map<Collectable, Count>! }

38. New avg wager Got a Collectable! A pay line win!

40. Betting small reduces avg wager! Bonus Game!

47. [<Measure>]! type Position! ! type MonopolyBoard =! {! Spaces : MonopolyBoardSpace [ ]! }! member this.Item with ! get (pos : int<Position>) =! this.Spaces.[int pos]

48. [<Measure>]! type Position! ! type MonopolyBoard =! {! Spaces : MonopolyBoardSpace [ ]! }! member this.Item with ! get (pos : int<Position>) = ! this.Spaces.[int pos]

50. And a pay line win! Coin size brought over from main game Houses = multiplier on wins GAME OVER Collected in the bonus game. Gives player extra ‘lives’.

51. type BonusGameState =! {! Board ! : MonopolyBoard! Position ! : int<Position>! Lives ! : int<Life>! Doubles! : int<Double>! CoinSize! : Wager! TotalWin! : Wager! }

52. Coin size brought over from main game

54. And a pay line win! Houses = multiplier on wins

58. Collected in the bonus game. Gives player extra ‘lives’.

60. 0<Position>

61. let jail = 6<Position>

62. let rec move newPos state =! match state.Board.[newPos] with! …! | GotoJail when state.Lives = 0<Life> -> ! ! move jail state |> gameOver! | GotoJail ! ! -> move jail state! …

71. let rec move newPos state =! match state.Board.[newPos] with! …! | RailRoad true ! -> awardRailRoadMultiplier state! | Property n when n > 0 -> awardPropertyMultiplier n state! | ElectricityCompany true! | WaterCompany true -> awardUtilityMultiplier state! …

72. let rec move newPos state =! match state.Board.[newPos] with! …! | CommunityChest! -> playCommunityChestCard state! | Chance ! ! -> playChanceCard state! …

77. Recap

78. lightweight syntax to create types and hierarchies

79. great for domain modelling

80. make invalid states unrepresentable

81. clear, concise way to handle branching

82. better correctness

83. order of magnitude increase in productivity

84. Stateful Server

86. player states are big

87. Stateless Server DatabaseClient

88. 1:1 read-write ratio

89. stateless = ! Inefficient & Expensive

90. ServerClient Session 1 Session 2

91. ServerClient Database

92. Elastic Load Balancer S3 Auto scaling Group Server A Server B ... EC2 CloudFront Stateful Server

93. The Actor Model An actor is the fundamental unit of computation which embodies the 3 things! • Processing! • Storage! • Communication! that are essential to computation.! ! -Carl Hewitt* * http://bit.ly/HoNHbG

94. The Actor Model • Everything is an actor! • An actor has a mailbox! • When an actor receives a message it can:! – Create new actors! – Send messages to actors! – Designate how to handle the next message

95. Stateful Server • Gatekeeper! – Manages the local list of active workers! – Spawns new workers! ! • Worker! – Manages the states for a player! – Optimistic locking! – Persist state after period of inactivity

96. Stateful Server Game Server Player A Player B S3 Worker C Worker B Gatekeeper RequestHandlers Asynchronous

97. Stateful Server Game Server Worker C Worker B Gatekeeper Worker A ok RequestHandlers Player A Player B Asynchronous S3

98. Stateful Server Game Server S3 Worker C Worker B Gatekeeper Worker A RequestHandlers Player A Player B Asynchronous

99. Stateful Server Game Server S3 Worker C Gatekeeper Worker A RequestHandlers Player A Player B Asynchronous

100. Stateful Server Game Server Worker C Worker A Gatekeeper error RequestHandlers Player A Player B S3 Asynchronous

101. type Agent<‘T> = MailboxProcessor<‘T>! ! ! !

102. type Agent<‘T> = MailboxProcessor<‘T>! ! type Message = ! | Get of AsyncReplyChannel<…>! | Put of State * Version * AsyncReplyChannel<…>

103. type Agent<‘T> = MailboxProcessor<‘T>! ! type Message = ! | Get of AsyncReplyChannel<…>! | Put of State * Version * AsyncReplyChannel<…>

104. type Result<‘T> =! | Success! of ’T! | Failure! of Exception! ! ! !

105. type Result<‘T> =! | Success! of ’T! | Failure! of Exception! ! type GetResult = Result<State * Version>! type PutResult = Result<unit>!

106. type Agent<‘T> = MailboxProcessor<‘T>! ! type Message = ! | Get of AsyncReplyChannel<GetResult>! | Put of State * Version * AsyncReplyChannel<PutResult>

107. type Agent<‘T> = MailboxProcessor<‘T>! ! type Message = ! | Get of AsyncReplyChannel<GetResult>! | Put of State * Version * AsyncReplyChannel<PutResult>

108. type Worker (playerId) =! let agent = Agent<Message>.Start(fun inbox ->! let state = getCurrentState playerId! ! let rec workingState (state, version) = ! async { … }! and closedState () =! async { … }! ! workingState (state, 1))

113. let rec workingState (state, version) = ! async { ! let! msg = inbox.TryReceive(60000)! match msg with! | None -> ! do! persist state! return! closedState()! …! }!

116. non-blocking I/O

119. let rec workingState (state, version) = ! async { ! let! msg = inbox.TryReceive(60000)! match msg with! …! | Some(Get(reply)) ->! reply.Reply <| Success(state, version)! return! workingState(state, version)! …! }!

120. let rec workingState (state, version) = ! async { ! let! msg = inbox.TryReceive(60000)! match msg with! …! | Some(Put(newState, v, reply)) when version = v ->! reply.Reply <| Success()! return! workingState(newState, version+1)! …! }

121. let rec workingState (state, version) = ! async { ! let! msg = inbox.TryReceive(60000)! match msg with! …! | Some(Put(_, v, reply)) ->! reply.Reply <| Failure(VersionMismatch(version, v))! return! workingState(state, version)! }

122. let rec workingState (state, version) = ! async { ! let! msg = inbox.TryReceive(60000)! match msg with! | None ! ! ! ! ! ! ! -> …! | Some(Get(reply)) ! ! ! ! ! -> …! | Some(Put(newState, v, reply)) when version = v ! -> …! | Some(Put(_, v, reply)) ! ! ! ! -> …! }

123. and closedState () = ! async { ! let! msg = inbox.Receive()! match msg with! | Get(reply) ->! reply.Reply <| Failure(WorkerStopped)! return! closedState()! | Put(_, _, reply) ->! reply.Reply <| Failure(WorkerStopped)! return! closedState()! }

124. and closedState () = ! async { ! let! msg = inbox.Receive()! match msg with! | Get(reply) ->! reply.Reply <| Failure(WorkerStopped)! return! closedState()! | Put(_, _, reply) ->! reply.Reply <| Failure(WorkerStopped)! return! closedState()! }

126. 5x efficient improvement

127. 60% latency drop

128. no databases

129. need to ensure server affinity

130. need to balance load

131. need to avoid hotspots

132. • Persist player state after short inactivity! • Move player to another server after persistence

133. need to gracefully scale down

134. Recap

135. Agents! • no locks! • async message passing! !

136. Agents! • no locks! • async message passing! • self-contained! • easy to reason with

137. Agents! • low level! • exceptions kills agents! • primitive error monitoring! • no supervision! • no distribution

138. MS Orleans Cricket akka.Net

140. Async Workflow! • non-blocking I/O! • no callbacks

141. Pattern Matching! • clear & concise

142. Replacing a large class hierarchy

144. Caught a Gnome

145. EXP Item Gold Quest Progress Caught a Gnome

146. Level Up Quest Progress EXP Item Gold Caught a Gnome Quest Complete

147. Level Up Quest Progress EXP Item Gold Caught a Gnome New Quest Quest Complete

148. Quest Progress EXP Item Gold Caught a Gnome Quest Complete New Quest Level Up

149. Quest Progress New Quest Achievement Progress EXP Item Gold Quest Complete Level Up Caught a Gnome

150. Level Up Quest Progress EXP Item Gold Caught a Gnome Quest Complete New Quest Achievement Progress Achievement Complete

151. Level Up Quest Progress EXP Item Gold Caught a Gnome Quest Complete New Quest Achievement Progress Achievement Complete

152. 100+ actions

153. triggered by different abstraction layers

154. non-functional requirements

155. message-broker pattern

156. Caught Gnome Trapping Queue Levelling Quests Achievements Analytics Partner Reporting

157. Caught Gnome Trapping Queue Levelling Quests Achievements Analytics Partner Reporting Ignore Process Process Process Process Ignore

158. Caught Gnome Trapping Queue Levelling Quests Achievements Analytics Partner Reporting EXP Item Gold

159. Caught Gnome Trapping Queue Levelling Quests Achievements Analytics Partner Reporting EXP Item Gold

160. Caught Gnome Trapping Queue Levelling Quests Achievements Analytics Partner Reporting EXP Item Gold Process Ignore Ignore Ignore Process Ignore

161. Caught Gnome Trapping Queue Levelling Quests Achievements Analytics Partner Reporting EXP Item Gold Level Up

162. Caught Gnome Trapping Queue Levelling Quests Achievements Analytics Partner Reporting EXP Item Gold Level Up

163. need lots of facts

165. type Reward =! | GotExp! ! of Exp! | GotGold! ! of Gold! | GotItem! ! of Item * Count! ! type StateChange =! | LevelUp! ! of OldLevel * NewLevel! …

166. type Fact =! | StateChange! of StateChange! | Reward! ! of Reward! | Trapping! ! of Trapping! | Fishing! ! of Fishing! …

167. let process fact =! match fact with! | StateChange(stateChange)! -> …! | Reward(reward)! ! ! -> …! | Trapping(trapping)! ! -> …! …

168. C# interop

169. …! var fact = Fact.NewStateChange(! ! StateChange.NewLevelUp(oldLvl, newLvl));! …

170. type IFact = interface end! ! type Reward =! | GotExp! ! of Exp! | GotGold! ! of Gold! | GotItem! ! of Item * Count! interface IFact

171. type IFact = interface end! ! type Reward =! | GotExp! ! of Exp! | GotGold! ! of Gold! | GotItem! ! of Item * Count! interface IFact

174. simple

175. flexible

176. extensible

177. saver

178. April 2015

179. Fri 8.30am, Salon H @theburningmonk / theburningmonk.com

180. Fri 8.30am, Salon H Fri 2.45pm, Guava + Tamarind @theburningmonk / theburningmonk.com

F# in social gaming (CodeMash 15)

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