F# in real world (LambdaCon15)

1. Yan Cui (@theburningmonk) BOLOGNA 28 march 2015 LambdaCon F# in the Real World

2. agenda

3. Hi, my name is Yan Cui.

5. 1MILLION USERS ACTIVE DAILY

6. 250MILLION DAY PER REQUEST

7. 2MONTH TB P E R sec ops 25,000

8. why F#?

9. time to market

10. correctness

11. efficient

12. tame complexity

13. 17th April! London

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

16. • 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

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

18. What the player’s new average wager?

19. Should the player receive collectables?

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

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

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

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

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

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

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

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

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

29. make invalid states unrepresentable

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

31. you’re never too smart to make mistakes

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

33. 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

34. 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

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

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

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

42. Betting small reduces avg wager! Bonus Game!

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

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

52. 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’.

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

54. Coin size brought over from main game

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

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

62. 0<Position>

63. let jail = 6<Position>

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

73. 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! …

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

79. Recap

80. lightweight syntax to create types and hierarchies

81. great for domain modelling

82. make invalid states unrepresentable

83. clear, concise way to handle branching

84. better correctness

85. order of magnitude increase in productivity

88. player states are big

89. Stateless Server DatabaseClient

90. 1:1 read-write ratio

91. stateless = ! Inefficient & Expensive

92. ServerClient Session 1 Session 2

93. ServerClient Database

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

95. 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

96. 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

97. 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

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

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

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

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

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

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

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

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

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

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

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

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

110. 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))

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

118. non-blocking I/O

121. 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)! …! }!

122. 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)! …! }

123. 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)! }

124. 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)) ! ! ! -> …! }

125. 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. 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()! }

128. 5x efficient improvement

129. 60% latency drop

130. no databases

131. 90+% cost saving

132. need to ensure server affinity

133. need to balance load

134. need to avoid hotspots

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

136. need to gracefully scale down

137. Recap

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

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

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

141. MS Orleans Cricket akka.Net

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

144. Pattern Matching! • clear & concise

147. Caught a Gnome

148. EXP Item Gold Quest Progress Caught a Gnome

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

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

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

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

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

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

155. 100+ actions

156. triggered by different abstraction layers

157. non-functional requirements

158. message-broker pattern

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

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

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

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

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

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

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

166. need lots of facts

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

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

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

171. C# interop

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

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

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

177. simple

178. flexible

179. saver

181. @theburningmonk github.com/theburningmonk theburningmonk.com

183. http://hire.jobvite.com/m?3OHq4hwL F# C# AWS Erlang Docker micro-services elasticsearch redis Google AppEngine Google BigQuery PostSharpNeo4j Python DevOps PagerDuty NewRelic

184. BOLOGNA 28 march 2015 LambdaCon Leave your feedback on Joind.in! https://joind.in/13652

F# in real world (LambdaCon15)

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