1. Proving correctness of a multiplayer game server Nirmalya Sengupta Freelance Software Technologist Nirmalya Sengupta

2. Background

• • Dutch company, decided to enter Online Poker market

• • Indian start-up given the job of development, deployment and support

• • Scope: an entire betting game environment

• • First version to be deployed in 12 months time

Nirmalya Sengupta

3. Application: a birds eye view Nirmalya Sengupta Player Portal Game Server Lobby Server Tournament Server Database RabbitMQ

4. Servers must be ...

• • Robust

• • Network ready

• • Support for Statefulness

• • Easy to interface with external systems

• • Highly threaded

• RedDwarf (previously Darkstar)

Nirmalya Sengupta

5. Important aspects of Server

• • Reactive to Events : Events give rise to other Events

• • Actions on Events are taken by Tasks (piece of code)

• • Tasks are scheduled (asynchronous), not executed immediately

Nirmalya Sengupta

6. Important aspects of Functionality

• • Randomness : legal requirement

• • Arbitrarily fired Timer s: necessity

• • Network connection with player can drop anytime: game must continue

• • Multiple simultaneous tables & tournaments

• • Game History must be retained : legal requirement

Nirmalya Sengupta

7. Important aspects of Design

• • Home-grown binary protocol between client and server

• • Application waits for and reacts to Event s only

• • Accurate detection of network connections availability

• • Tasks handle Event s ( asynchronously )

• • Database plays an adjunct role (post-facto)

Nirmalya Sengupta

8. Picture: player joins while game is continuing Nirmalya Sengupta

9. Picture: Player plays on two tables, leaves one Nirmalya Sengupta Real World (Player using client software) Virtual World (Player represented in server software) Network connection

10. How to test a software which..

• • is distributed

• • is completely asynchronous

• • is asking testers to be good Poker players

• • is affected by Timers (arbitrariness)

• • Must withstand tens of thousands of simultaneous Players

• • is expected to display minimum latency always

Nirmalya Sengupta

11. Steps taken to increase testability

• • Gamerules and Business rules contained in a FSM

• • Robot s written which could play Poker

• • Binary protocol carried Roundtrip time data

• • Facility to fire pre-configured Timers

• • Specialized Sniffer tasks deployed

• • Handcrafted cards were dealt to players

• • Deployed Event pattern detection ( Esper )

Nirmalya Sengupta

12. Our observations

• • Designer must consider phases of QA , Deployment and Support while designing structure and feature

• • Asynchronous, Event-driven software offer different challenges and benefits

• • QA team of programmers: considerable benefits

• • Automation: functionality and performance

Nirmalya Sengupta

13. Questions? Nirmalya Sengupta