This document discusses using Akka frameworks to build an MMOG server, including the actor model, messaging patterns, persistence, streams, remoting, clustering, HTTP integration, and testing. It provides an example of modeling an online game of Housie using Akka frameworks and persisting game events. References for further reading on Akka and building multiplayer games are also included.

1. Levelling up in Akka
Building an MMOG server
Ajay Viswanathan, Sr. Software Engineer, Sigmoid

2. Intro to Akka
• The actor model
• Actor systems
• Messaging patterns
• Supervision of actors
• Handling state in Akka
• FSM in Akka

3. Akka Persistence
• Incoming messages plus current state abstracted as events
• Each event written to pluggable journal
• Events could be manually or auto-persisted
• Snapshot feature for faster recovery times

4. Akka Streams
• Generic abstraction for handling a wide variety of data I/O
• Basic stream is made up of Source -> <Flows> -> Sink
• Flows are composable
• DSL for creating complex graph flows

5. Akka Remote
• Allows an actor running on another JVM and ActorSystem to
communicate
• TCP/UDP communication available out of the box with Akka

6. Akka Cluster
• Allows actors running on multiple JVMs to form a shared actor entity
• New actors register with defined seed nodes
• Alternative is to use routers and a coordinating actor to handle loads
using a particular strategy (Round-Robin by default)
• Sharding API for granular selection of cluster actors for handling
loads

7. Akka HTTP
• For communicating with 3rd party services
• HTTP and WS protocol support out of the box
• Simple DSL for defining routes and integration with Streams

8. Akka Testkit
• Allows peeping inside actor for testing state
• Provides convenient TestProbe object for simplified testing simple
actors and FSM actors
• DSLs for testing HTTP routes and streams

9. Demo
• Modelling Housie (Tambola) as an FSM
• Connecting clients via websocket server
• Broadcast and reply messaging patterns
• Handling of Streams via custom protocol
• Persisting game events
• Repo link - https://github.com/ajatix/akka-housie

10. References
• http://chumper.github.io/2016/01/06/Akka-Game-From-Scratch.html
• http://doc.akka.io/docs/akka/current/scala/cluster-sharding.html
• http://doc.akka.io/docs/akka/current/scala/persistence.html
• https://github.com/JakubDziworski/Akka-Streams-Websocket-Game-Server
• https://speakerdeck.com/miciek/building-multiplayer-game-using-streams-v2
• https://github.com/miciek/snake-multiplayer-akka-streams/blob/master/src/main/scala/com/michalplachta/snake/Main.scala
• http://leveldb.org/
• http://nodejsconfit.levelgraph.io/#17
• https://github.com/boldradius/akka-exchange
• http://rxmarbles.com/
• https://github.com/dnvriend/akka-persistence-fsm
• https://sachabarbs.wordpress.com/2016/08/16/akka-persistent-actors/
• https://sachabarbs.wordpress.com/2016/09/06/akka-state-machines/
• https://sachabarbs.wordpress.com/2016/09/14/akka-testkit/
• http://tambola.kunals.com/content/nicknames