1

JBus, A Platform Independent Publish/Subscribe Bus for CWave

2000

M.S. Thesis Defense

Joseph W. Longson

March 30, 2000

2

Publish / Subscribe bus

BusClient

BusClient

BusClient

Pub/Sub bus

Implementation is like a chat room– Each member uses a room number for communication (topic)

– Allows multiple clients in the same room (topic)

– Transmit strings, pictures, sounds, etc (data)

Introduction

3

Platform Independent

Code does not rely upon a platform– Implemented for a virtual platform

– Multiple Operating Systems for clients (Mac, Windows, UNIX, etc)

– Multiple Hardware Platforms for clients (Mac, PC, SGI, SUN, etc)

Introduction

UNIXPlatform

MacPlatform

WindowsPlatform

BusClient

BusClient

BusClient

Pub/Sub bus

4

CWave 2000 Toolkit

Toolkit containing many components including– Environment for setting up bus clients

– Publish Subscribe bus implementation

Includes a Publish / Subscribe bus implementation– Based on Microsoft’s COM/DCOM, limited to the Windows platform

– Allows process and machine independent client interaction

Introduction

VBProgram

C++Program

MS JavaProgram

WindowsPlatform

WindowsPlatform

WindowsPlatform

CWave bus

5

Problem Statement

Problem: CWave 2000 not platform independent.– Limited to the Windows OS, on the PC platform

– Uses DCOM, which is designed for a LAN, not for the Internet

Solution: – Extend CWave 2000’s Publish / Subscribe bus

– Allow communication from other operating systems

– Allow non-COM languages to communicate with bus

Introduction

6

JBus

Provides a platform independent Publish / Subscribe bus

– Implemented in Java for the Java Virtual Machine

– Interfaces available for Java, C, and C++

Compatible with the CWave 2000 System– But not dependent on it

Introduction

VBProgram

C++Program

MS JavaProgram

WindowsPlatform

WindowsPlatform

WindowsPlatform

CProgram

JavaProgram

WindowsPlatform

UNIXPlatform

MacPlatform

JBus

Java Pub/Sub bus CWave Pub/Sub bus

C++Program

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Primary Design Constraints

Platform independence– Hard to achieve completely, so this will used as a guideline

Leverage the Internet for communication– Using HTTP and XML for message Transport

Maintain compatibility with CWave 2000– Compatible but not dependent on CWave

Modular design– Allows bus implementation to be easily replaced

Introduction

8

Secondary Design Constraints

Have a small memory and disk space footprint– This allows JBus clients such as Web Browsers to be developed

Platform independent data marshalling– This is a hard constraint that may not be solved

Support new and existing C/C++ clients– Extends the languages available for JBus client implementation

Entire system should perform at an interactive level– Performance will be tuned to a usable level

Introduction

9

Related Work

Introduction

Platform Inde-

pendence

HTTPCWave

compatibleModularDesign

SmallSize

DataMarshaling

C/C++Clients

Performance

CWave2000

no no yes no partial no yes yes

TIBCO partial no yes no yes no yes yes

Voyager yes no yes no partial no yes yes

iBus yes no maybe no partial no yes yes

JMS/JMQ

partial yes maybe no no partial partial yes

SOAP yes yes no no N/A partial no no

Siena no yes no no no no yes yes

JINI yes no no no yes yes no yes

JBus yes yes yes yes yes partial partial no

Product

Secondary ConstraintsPrimary Constraints

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Java BusImplementation

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JBus Representation

Provided the illusion of a single omnipresent bus– Platform independent (using Java)

– Topic based communication

JBus

JavaClient

Machine 1, Windows Machine 3, Web Browser

WebClient

JavaClient

Machine 2,UNIX C++

Client

Phase 1

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JBus Implementation

Implemented as a set of connected local buses– Each client has a local bus instance

– Transport objects used for communication between buses

– Each local bus acts as either a Server or Proxy

Phase 1

Machine 2, UNIX

JBus

JavaClient

Machine 1, Windows

C++Client

Transport Transport

JBus

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JBus Architecture

Bus Client Interface

Message Filtering

Message Transport

Bus Client Interface– Used to get a JBus instance

– Publish/Subscribe methods

Message Filtering– Routes messages to Bus

Clients

– Filtering of messages

Message Transport– Implemented as Bus Client

– Can have local filtering

– Communicates using desired medium (e.g. HTTP, SSL)

Phase 1

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JBus Client Example

Case 1, Java Client– Connects as a Bus Server

– Installs an HTTP Server on the local machine

Case 2, C/C++ Client– Connects as a Bus Proxy

– Remotely connects to a machine using the HTTP protocol

Phase 1

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2

Bus Factory

JavaClient

(1) - Java Client asks Bus Factory to create a Bus Server

HTTPServer

Bus Server

(2) - Bus factory creates Bus Server and HTTP Server

(3) - HTTP Server subscribes to bus and begins communicating with bus

(4) - Client begins communicating with bus

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Phase 1

Bus Factory

1

JBus Client Example Case 1: Java Client

Machine 1

16

Bus Factory

5

6

Bus Factory

(5) - C/C++ Client asks Bus Factory to create a Bus Proxy to a Server

(6) - Bus Factory creates a local Bus Proxy and a local Transport object

(8) - Communication commences between Transport Objects

JavaClient

HTTPServer

Bus Server

C/C++Client

Bus Proxy Transport

(7) - Remote HTTP Server creates a Transport Object for proxy connection

(9) - Client and Transports begin communicating with their buses

Transport7

89

Phase 1

JBus Client Example Case 2: C/C++ Client with Transports

Machine 1

Machine 2

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JBus Client Example Case 1 and 2 in action

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CWave 2000 GatewayObject

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Gateway Object Representation

Interfaces between the JBus and CWave 2000– Transparent to the client

– Allows communication from either implementation

Phase 2

JBus CWave 2000

Gateway

JBus interface

CWave interface

JavaClient

CWaveClient

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Gateway Object Implementation

Implemented as a JBus object– This provides a transparent interface for JBus clients

Uses Microsoft’s Extensions for Java– This allows communication with the CWave 2000 bus

Phase 2

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JBus Client Example

Case 3, CWave Client– Uses the Gateway Object

– Connects as a Bus Proxy

– Begins communicating with JBus or CWave bus clients

Phase 1

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10

Bus Factory

(11) - Bus Factory creates Gateway and Transports. Transports connect and begin communicating

JavaClient

HTTPServer

Bus Server

C/C++Client

Bus Proxy Transport

(10) - CWave Client asks Bus Factory to create a Gateway Proxy to Server

(12) - Client and Transports begin communicating with their buses

Transport

Phase 1

JBus Client Example Case 3: CWave Client with Gateway

CWaveClient

JBus Gateway Transport

Transport

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12

12

Machine 1

Machine 2

Machine 3

Bus Factory

11

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JBus Client Example Case 3 in action

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Data Marshalingwith XML

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Data Marshaling

What is Data Marshaling?– The translation of data from one

form to another

Where is it used?– Between Transport Objects

– Between Programming Languages

What options do we have?– BINARY

– ASCII

– XML

Phase 3

01 10110111

04 01011011

BINARY

183 c

ASCII

<INT>183</INT>

<CHAR>c</CHAR>

XML

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XML

Similar to HTML– ASCII format

– Uses the concept of Tags

Structure of XML– Stores the format with the data

– Multiple formats can be intermixed in a transmission

Why use?– Flexible

– Platform Independent

– Many parser implementations available.

<?xml version=1.0”?><CWAVE> <CM t=”Hello” f=”SIMPLE”> <SIMPLE> <STRING>World</STRING> </SIMPLE> </CM> <CM t=”Hello” f=”COMPLEX”> <COMPLEX n=“2”>

<STRING>World</STRING> <FLOAT>3.14159</FLOAT>

</COMPLEX> </CM></CWAVE>

Phase 3

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What to Marshall?

Easy Hard

Primitives: Int, Float, Char, etc

Multi-element A: AnEvent, Java Vector

Complex:Struct, Class

Subtyping:Inherited classes, Multiple class instances

JBus 1.0

Multi-element B: general collectionclasses

Phase 3

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Bus Factory

JavaClient

HTTPServer

Bus Server

C/C++Client

Bus Proxy Transport

(13) - Properly Marshal data between the Client and the bus, and between Transports

Transport

Phase 1

JBus Client Example with Data Marshaling

CWaveClient

JBus Gateway Transport

Transport

Machine 1

Machine 2

Machine 3

13

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JBus Client Example with Data Marshaling in action

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Performance Results

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Preliminary PerformanceSingle Process Subscriber Notify Time

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

100 1,000 10,000 100,000

Number of Messages

Me

ssa

ge

s p

er

Se

con

d

1

5

10

25

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Preliminary PerformanceSingle Process Subscriber Notify Time

with Gateway Object

0

100

200

300

400

500

600

100 1,000 10,000

Number of Messages

Me

ssa

ge

s p

er

Se

con

d

1

5

10

25

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Preliminary Performance

Network Subscriber Notify Time

0

20

40

60

80

100

120

100 1,000 10,000

Number of Messages

Me

ssa

ge

s p

er

Se

con

d

Transmit and Parse

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Conclusion

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Contributions

Platform independent extension to CWave 2000– Extends client implementation choice

– Extends CWave communication to the Internet

Message Transport using XML over HTTP– Allows more Platform independent data marshaling

Can function with or without CWave 2000– Allows use of the JBus beyond CWave 2000

Modular bus design– More flexible for bus experimentation

Conclusion

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Future Research

Performance Tuning

Better data marshaling for complex data types

Enhance the ability for thin clients to use the JBus

Conclusion

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Questions?

Thank you!

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Preliminary Performance 2Single Process Subscriber Notify Time

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

1 5 10 25

Number of Messages

Me

ss

ag

es

pe

r S

eco

nd

100

1,000

10,000

100,000

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Preliminary Performance 2Single Process Subscriber Notify Time

with Gateway Object

0

100

200

300

400

500

600

1 5 10 25

Number of Messages

Me

ssa

ge

s p

er

Se

con

d

100 Messages

1,000 Messages

10,000 Messages

40

Preliminary Performance 2

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Extensions

C/C++ Extension

Web Extension

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JBus++ Extension (C/C++)

Extension to the JBus Client Interface

– Allows C or C++ clients to use the JBus functionality

– Relies upon the JNI from Sun

Data Marshaling– XML

– JNI Data Types

JBus Client Interface

Message Filtering

Message Transport

JBus++ Client Interface

Extensions

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Web Extension

HTTP Transport– Allows Firewall Penetration

– Works with Proxy Servers

Web Clients– Create a Web Server

– Serves Web pages with embedded Applets

Thin Clients– Use the JME (Java Micro Edition)

– Download Applets

Extensions

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Research Progression

Phase 1– Java version of the bus

– Simple TCP/IP communication

Phase 2– CWave 2000 Gateway

Phase 3– Data Marshalling using XML

– HTTP communication

Introduction

Extensions– C/C++ clients

– Web Interface