Games, chat, and finance

1
Games, chat, and finance Toward a truly
interactive web with Comet, BAM, and HMTP
Emil Ong Chief Evangelist
2
Caucho Technology

• Resin has been around for 10 years
• Over 8000 customers, even more open source users
• User base consists of both early and conservative
  adopters
• Now the top Java web server in NetCraft
• http//survey.netcraft.com/Reports/200805/
• 340,000 domains

3
Groundbreaking Innovations

• Hessian web services protocol
• Top clustering implementation
• Quercus PHP in Java
• Server-push
• And now... a revolutionary approach to the
  interactive web

4
The Interactive Web

• Common properties
• Sessions are long-lived
• Must be responsive/ real time
• Must not overburden server
• Communication is bidirectional

• Killer apps
• Games
• Chat
• Finance

5
The Interactive Web with HTTP

• Sessions are long-lived
• Must be responsive/real time
• Must not overburden server
• Communication is bidirectional
• This is harder with HTTP

Comet has shown this is possible
6
Simulating Bidirectional Communication with HTTP

• Client generated events are easy
• They are simply requests
• AJAX just makes those requests without changing
  the page
• What about the other direction?

7
Sending events from server to client using HTTP

• Polling
• Requests at regular intervals that complete
  immediately
• Long Polling
• Requests that wait for the next event, then
  restart
• Server-push (Comet)?
• Socket held open with streaming updates from the
  server

8
Techniques compared
9
Server-Push (Comet)?

• Current hot technology
• Implementations
• Resin
• Grizzly (Glassfish)?
• Jetty
• Tomcat
• All solve the problem of threads dedicated to a
  socket
• All have a different programming model

10
The problem of Bidirectional Communication with
HTTP

• Different techniques for send and receive
• Use AJAX to send data from client
• Use Comet to receive data on client
• Two connections required
• Places limitations on TCP that were necessary for
  scalability in the past
• A necessary evil at the moment

11
Truly Interactive Communication

• Must be capable of long-lived connections
• Must be responsive/real time
• Must not overburden server
• Must be bidirectional
• Must have a simple, coherent API/architecture

12
Creating the architecture

• Start with the communication patterns
• Messages
• Request/response
• Truly bidirectional communication
• Client - Server
• Server - Client
• Both must be supported in both patterns

13
Creating the architecture

• Representation of entities
• Agents
• Bidirectional communication implies that clients
  are first class citizens
• Agents represent both clients and servers
• A broker manages communication between agents

14
Brokered Agent Messaging (BAM)?

• Broker
• Handles communication between
  agents
• It's not CORBA
• Agents
• Represent both clients and services
• Messaging
• Messages
• Request/response (asynchronous)?

15
Example Sudoku

• Demo

16
Logging In
Resin
Client 1
Login Query
Client Agent 1
Broker
Client Agent 2
Client 2
Login Query
Sudoku Service
17
Starting a game
Resin
Avatar Agent 1
Client 1
Client Agent 1
Start Query
Broker
Game 1
Avatar Agent 2
Client Agent 2
Client 2
Start Query
Sudoku Service
Wait Result
Start Result
Start Message
18
Making a Move
Resin
Avatar Agent 1
Client 1
Client Agent 1
Move Query
Broker
Move Message
Move Result
Game 1
Avatar Agent 2
Client Agent 2
Client 2
Sudoku Service
19
Ending the Game
Resin
Avatar Agent 1
Client 1
Client Agent 1
Move Query
Broker
Move Message
Move Result
Game over Message
Game over Message
Game 1
Avatar Agent 2
Client Agent 2
Client 2
Sudoku Service
20
Design notes

• Agents can be long-lived
• SudokuService
• Client
• Agents can be short-lived
• SudokuAvatar
• Agents are lightweight and dynamic
• Non-agents can interact with the system
• SudokuGame

21
Code sample SudokuAvatar

• public boolean sendQuerySet(long id,
• 
  String to, String from,
• 
  Serializable value)?
• if (value instanceof MoveQuery)
• MoveQuery query (MoveQuery) value
• MoveResult result _game.move(query,
  getJid())
• _broker.sendQueryResult(id, from, to,
  result)
• return true
• ...

22
BAM API

• void sendMessage(String to,
  String from,
  Serializable value)?
• boolean sendQueryGet(long id,
  String to,
  String from,
  Serializable query)?
• boolean sendQuerySet(long id,
  String to,
  String from,
  Serializable query)?

23
Address space

• Agent names look like email addresses
• sudoku_at_caucho.com/3
• First component service name (sudoku)?
• Second component domain (caucho.com)?
• Third component instance identifier (/3)?
• Address structure reflects lightweight nature of
  agents

24
Hessian Message Transfer Protocol(HMTP)?

• Wire protocol on which BAM is based
• Uses Hessian for compact serialization
• Evolved from XMPP (Jabber)?

25
Target platforms

• Flash/Flex
• Silverlight
• JavaFX
• Java Applets
• Comet (interim)?
• Java
• Quercus (PHP)?
• .NET

26
Conclusion

• Interactive applications will become more common
• HTTP is not sufficient to handle them
• BAM outlines a new architecture and API to make
  the development of these applications easier

27
What's next?

• Technical
• Convenience functions
• Making a PHP page a BAM service
• HMTP standardization
• Promotional
• Game contest

28
Thank you!

• Questions?
• Comments?

29
More information

• http//hessian.caucho.com/
• http//blog.caucho.com /

30
Appendix Bridging BAM and Comet

• Initial Comet request creates agent
• Agent triggers event to client on messages
• On AJAX requests, pull agent name from session