1

Jini™ ConnectionTechnology

Architecture OverviewBill Day

bill.day@sun.comwww.billday.com

Technology EvangelistSun Microsystems

Agenda

l Why Jini?l What is Jini?l Jini Architecture Overviewl The Detailsl Example Service Modelsl Subtopics on:uJavaSpaces™

uJini Surrogate ArchitectureuRelated Technologies

l Availability and Resources

2

Why Jini?

Distributed computing is moredifficult than local computingbecause of:

Why Jini?

l Network latencyl Concurrency issuesl Memory managementl Inevitable partial failure

3

Evolution of distributedcomputing

MessagePackets

MessagePackets

RemoteProcedure

Calls

RemoteProcedure

Calls

DistributedObject

References

DistributedObject

References

DistributedObjects

DistributedObjects

TCP/IP Sockets

C/C++Administrative ToolsFixed Topology

CORBA/IIOP or DCOMMultiple LanguagesAll Computation on ServerStatic Server Locations

RMI/IIOPJava™ OnlyDistributed Client/Server LoadDynamic Server Locations

Key insight: Remote increasingly looks local

What is Jini?

4

l Jini addresses the problems ofdistributed computing using a set ofsimple interfaces and protocols

l Jini enables spontaneous networks ofsoftware services (and devices) toassemble into working groups ofobjects, or Federations

l Jini enables self-healing when oneor more devices are removed fromthe Federation

l Jini builds on the Java™ 2 Platform

What is Jini™?

What is Jini™?

l Jini is usable for hardware as well assoftware servicesuEverything is represented by Java

Objects.uEverything is located and accessed

through Java Interfaces.

5

The Value of Jini™

l ConsumersuPlugging in networked devices and

application software is as simple asplugging in a phone today

l Service providersuSimplifies management of application

service delivery

The Value of Jini™

l Product manufacturersuOpens entirely new markets

(diagnostics, post-purchase upgradesand software enhancements, customercare)

l ProgrammersuSimplifies the task of writing distributed

applications by freeing them fromnetwork topology

6

Jini Architecture Overview

SPARC™ PPC x86

Solaris Mac Windows

Java Java Java

Lookup

JavaSpaces™ Other Services

JiniInfrastructure

JiniServices •••

Discovery/Join

RMI

TM

Jini™ Architecture Overview

7

Java Technology Features thatBenefit Jini™

Feature

Java Virtual Machine

Portable object code

Downloadable code

Unified type system

Benefit

Homogeneous network

Architecture independence

Dynamic environment

No impedance mismatch

Jini Extends the Java Platform

Jini

Java

ServicesInfrastructure Programming Model

Discovery

Lookup

ExtendedSecurity

Java VM

RMI

Security

Lease

Event

Transaction

Javatechnology-based APIs

Beans

Swing

JavaSpaces

TX Manager

OtherServices

EnterpriseJavaBeans™

Java Namingand DirectoryInterface™

JTS

8

The Details:Jini Infrastructure

Jini Lookup Service

l Repository of available servicesl Stores each service as Java objectsl Clients download services on demand

Lookup Service

(LUS)

Service Proxies

9

Using a Lookup service

JiniLookupService1. Java.ty

pe

2. Service

O

bject

Client 3. Request

4. Response

Device or Service

Lookup service

l May be federated with other lookupservices

l Lookup service interface provides:uRegistration, Access, Search, Removal

10

Discovery and Join Protocols

l Used to find and join a group ofservices.

l Based on UDP multicast.l Services advertise capabilities.l Provide required software drivers.l Establish reference with lookup

service.l Unicast discovery also supported.

Discovery Protocol

UDP Multicast

LUSLUS

LUSLUS

LUSLUS

Network ServiceNetwork Service

11

Join Protocol

ServiceProxy

ServiceProxy

ServiceProxy

ServiceProxy

Network ServiceNetwork Service

LUSLUS

LUSLUS

Steps in Discovery and Join

l Jini™ enabled Object (representinga hardware and/or software service)multicasts a packet with a referenceto itself

l The service receives RMI referenceto Lookup service (one or more)

l The service joins a Federation byplacing an object representing itscapabilities into the Lookup servicefor other clients and services to use

12

Discovery and Join: Traditionalversus Jini™ Technology

TraditionalTechnology

l Device is addedto computer

l Device definition isedited in nodeconfiguration table

l Computer is restartedl Updated configuration

table is pushed tonetwork device map

Jini Technolgyl Device is plugged in

and powered upu Lookup service

receives multicastu Lookup service

authenticatessource

u Lookup servicesendsadvertisement

u Device joinsLookup service

Finding a Service

l To find a service, a Jini client locatesservice by querying a Lookup Serviceby type (Java Interface).

l Code moves from service to client viaLookup Service.

l Code needed to use service isdynamically loaded on demand.

13

Finding a Service

Service RequestServiceProxy

ServiceProxy

Network ClientNetwork Client

LUSLUS

Using a Service

l Communication is betweenservice and its proxy

l Independent of wire protocoll Protocol can change without

affecting clientl RMI semantics core to functionality

14

Using a Service

Any ProtocolNetwork ServiceNetwork ServiceService

ProxyServiceProxy

NetworkClientNetworkClient

Why Jini™ uses RMI

l RMI can pass entire Java objects andtheir code

l Works in any compliant JVMl Provides automatic serialization,

transport, and de-serialization ofobjects

l Robust and configurable securityoptions (RMI over SSL, AuthenticatedPrincipal, etc.)

15

The Details:Programming using Leases,

Events, and Transactions

Why Distributed Leasing?

l Problem: Partial failure in distributedsystems can lead to uncheckedresource consumption

l Traditional solution: systemadministrationuError-proneuCostlyuOnly happens when it’s too late

16

Distributed Leasing in Jini™

l Protocol for managing resources usinga renewable, duration-based model

l Contract between objectsl Resources can be shared or privatel Provides a method of managing

resources in an environment wherenetwork failures can, and do, occur

What are Leases?

l Time-based grants of resourcesor services

l Loose contracts between grantorand holder

l Negotiated for a set period of timel Can be shared or exclusive

17

Lease Operations

l Leases may be:uCancelled (explicit cleanup)uRenewed (explicit extension)uAllowed to expire (implicit cleanup)uObtained and manipulated by third parties

Distributed Leasing

l Resources are allocated only aslong as continued interest is shown

l Leasee is responsible to renew leasebefore expiry

l The network is self-healing

18

Distributed Events

l Extend Java™ event model to work ina distributed network

l Register interest, receive notificationl Allow for use of event managersl Support various delivery modelsuPush, pull, filter

l Use the Distributed Leasing protocol

Transaction model in Jini™

l Designed for distributed objectcoordination

l Light weight, object-orientedl Supports two-phase commitsl Uses Distributed Leasing protocoll Implemented in Transaction Manager

service

19

The Details:Jini Services

Services

l Represented by Java InterfacesuSeparation of “how” from “what”u Implement in hardware or softwareu Implementations can change over timeuMultiple implementations

l Set of services open endeduDevicesuSoftware servicesuBusiness objects

20

Services Enable Evolution

l Base interfaces can be extended to:uAdd new functionalityuCombine functionality

l Old clients can use base interfacel New clients can use extended

interfacel Allows evolution of implementation

without changing clients orinfrastructure

Services Are Definedby Java Interfaces

I’m a Printer

I’m a ColorPrinter, therefore a Printer too

InterfacePrinter

InterfacePrinter

InterfaceColorPrinter

InterfaceColorPrinter

21

Services Defined by Interfaces

I’m a PhotoCopier and a Printer

I’m a FaxMachine, a PhotoCopier,and a Printer

InterfacePrinter

InterfacePrinter

InterfacePhotocopier

InterfacePhotocopier

InterfaceFaxMachine

InterfacePhotocopier

InterfacePhotocopier

InterfacePrinter

InterfacePrinter

Client Finds Serviceby Interface

Give me a PhotoCopierNetworkClient

NetworkClient LUS

InterfacePhotocopier

InterfacePhotocopier

22

Client Finds Serviceby Interface

InterfacePrinter

InterfacePrinter

InterfaceColorPrinter

InterfaceColorPrinter

Give me a PhotoCopierLUSNetwork

ClientNetwork

Client

Client Finds Serviceby Interface

Give me a PhotoCopierLUS

InterfacePrinter

InterfacePrinter

NetworkClient

NetworkClient

23

Enabling Services

l Transaction manageruDefault service implementation.

l Jini 1.1 Utility ServicesuLookup Discovery service, manages

discovery on behalf of its clients.uLease Renewal service, receives and

stores remote event notifications onbehalf of its clients.

uEvent Mailbox service, manages leaserenewal activities on behalf of its clients.

Service Interfaces

l Community drivenuPrintinguService UI

l Don’t have to be done by Sunl Only base types need to be commonl Interfaces can evolveuNew apps can use new functionalitiesuOld apps still work

24

Legacy Services

l Jini requires Java at the networkuServices identified by Java typeuProxies may need code downloaded

l Implementation can be non-JavauWrap legacy language in JavauMake calls to legacy with JNI

Example Service Models

25

Proxy

Client

Java VM

Service Client

Dev 1 Dev 2 Dev 3JavaDeviceBay

RMI

PrivateProtocol

Example service model #1:Local device concentrator

Exposing a disk cluster as a single networked file store

ServiceProxy

Proxy

ClientJava Embedded Server

Service Client

Service Proxy

Dev 2 Dev 3

RMI

Dev 1

PrivateProtocol

Example service model #2:Remote device concentrator

Home network (AV equipment, appliances, etc.) communicate via Java Embedded Server™

26

Proxy

ClientJava VM

Service Client

Service Proxy

RMI

RMI, CORBA/IIOP,DCOM

Example service model #3: EJBservices

Accessing enterprise resources

EJB Server

HTTP, SHTTP Java VM

Enterprise resources

Detailed Example: Jini-Enabled Printer

Java VMJava VM

Jini InfrastructureJini Infrastructure

Drivers

GUIGUI

27

Discovery

l Multicast query for lookup service

UDP Multicast

LUS

Discovery

l Lookup service discovered

LUSLUS

28

Join

l Printer registers service objectwith LUS

LUSLUS

Locating Service

l Client asks LUS for Printer

LUSLUS

Printer?

29

Locating Service

l LUS returns printer serviceobject to client

LUSLUS

Using the Service

l Client communicates to printerthrough service object

LUSLUS

30

JavaSpaces™

What Is JavaSpaces?

l A Jini™ Servicel A Persistent Shared Object Storel Transactionally Securel Astonishingly Simplel Based on “tuple-spaces”

(see David Gelernter’s Linda system)

31

JavaSpaces Design

l Parallel programmingl Distributed systemsl Cooperating software ensembles

space

entries

JavaSpaces Benefits

l Anonymity between applicationsl Uncoupled communicationl Programs can communicate

through time or spacel Vast savings in design and

development time

32

JavaSpaces Concepts

l High-level communications betweenJava program

l SIMPLE: only a few operations to learnl EXPRESSIVE: a large number of

computing problems can be solved

JavaSpaces Programs

l Processes do not directly interactl Processes interact indirectly through

one or more spaces

33

What Is a Space?

l Persistent object storel Network accessiblel Sharedl Transactionally securel Can store executable content

Modification of Entries

l An Entry in a space cannotbe modified

l Must be taken, modified, written

process

process

process

modify

take

write

34

Matching Entries

l A template is used to match entriesin a space

l The template is simply an entry ofthe type to be matched

l Fields of the entry are used for matchingl Non-assigned fields are wildcards

Entries

l Entries are collections of typed objectsl Must implement net.jini.core.entry.Entryl Fields can be any serializable

Java™ objectl Fields must be public to be matchablel Entry needs no-arg constuctor

35

Example Entry

l This shows a minimal entry:

public class SpaceShip implements Entry {

public String name; public Integer score; public SpaceShip() {

}

}

Accessing a Space

l Jini is used to locate a spacel Sun’s implementation identifies

spaces by namel Convenience method from

JavaSpaces book:

SpaceAccessor.getSpace("name");

36

Space Operatons

l Very small number of operations aredefined on a space

l The three fundamental operations are:uWriteuReaduTake

Write Operation

l Writes an entry to a space

process write

37

Write Operation

l Instantiate an Entryl Set its fields as necessaryl Write the entry to the space

SpaceShip s = new SpaceShip();s.name = "USS Enterprise";

space.write(s, null, Lease.FOREVER);

Read Operation

l Reads an entry from a spacel Copy of object is returnedl Original remains in space

process read

38

Read Operation

l Build a templatel Read a matching entry from the space

SpaceShip template = new SpaceShip();template.name = "USS Enterprise";SpaceShip s = space.read(template, null, Long.MAX_VALUE);

Take Operation

l Takes an entry from a spacel Matched entry is removed from space

process take

39

Take Operation

l Build a templatel Take a matching entry from the space

SpaceShip template = new SpaceShip();template.name = "USS Enterprise";SpaceShip s = space.read(template, null, Long.MAX_VALUE);

Other Space Operations

l ReadIfExists()uNon-blocking read

l takeIfExists()uNon-blocking take

l Notify()uInform me when a matching entry

is written to the space

40

JavaSpaces Patterns

l Distributed Data StructuresuMultiple entries stored in one

or more spacesl ProtocolsuApplication-defined way to

manipulate/access data structures

Example: Distributed Array

l Each array element is an entryin a space

l Entry stores content and positionin array

l Protocol is defined to add/removearray elements

EndInteger position

ArrayElementInteger position Object content

41

Example: Distributed Array

l Multiple processes concurrentlyaccess the array through the space

processprocess

process

JavaSpaces Leases

l Based on Jini lease modell Resources allocated for fixed

time periodl Lease is specified when entries

are written to spacel When the lease expires, the space

removes the entry from its store

42

JavaSpaces Leases

l Lease time is parameter towrite operation

l Specified in milliseconds inSun’s implementation

l Lease object is returned by write()

Long duration = 1000*60*5; // 5 minutes

Lease 1 = space.write(ship, null, duration);

JavaSpaces Transactions

l JavaSpaces operations aretransactionally safe

l All operations are atomicl Multiple operations may be grouped

using a transaction objectl Based on Jini transaction modell Transactions may span multiple

spacesl Spec supports nested transactions

43

Example Application

l Image processingl Goal: perform operation on

every pixel in large imagel Problem: image ops are

computationally expensivel Solution: JavaSpaces

Example Application

l Perform edge detection on this image

44

Example Application

l Step 1: Divide image into titles

Example Application

l Step 2: Build Entry object for each tilel TileEntry contains code to

perform operation

Client Process

TileEntry

45

Example Application

l Step 3: Write tile entries to space

Client Process

Example Application

l Step 4: Server process concurrentlytakes tile entries from space (blockingif not available)

Server Process

take

46

Example Application

l Step 5: Server process executes code(contained in TileEntry) to processthe tile

Server Process

Example Application

l Step 6: When finished processing,server writes completed tile back tospace, after setting its FINISHED flag

Server Processwrite

47

Example Application

l Step 7: Concurrently, client takesFINISHED entries from space(blocking if not available) andreconstructs image

Client Process

take

Pure Scalability

l Want to process more images?l Just add more clients/server

Client Process

Client Process

Client Process

Server Process

ServerProcess

ServerProcess

ServerProcess

ServerProcess

48

Advantages

l Servers can be any platform thatsupports Java

l Can mix and match serversl Server needs no prior knowledge

of image operationl Highly scalablel Highly flexiblel Highly reliablel Simple design

JavaSpaces™ at JavaOne 1998

49

Jini™ Surrogate Architecture

Jini Surrogate Architecture

l Not every device supports a full Java™

2 Standard Edition (J2SE) virtualmachine.

l Even if a device does support Javatechnology (say through J2ME), it maynot have enough memory or meetother requirements to support a full Jiniimplementation.

l However, any networkable device canproxy via a surrogate that supportsJava and Jini technologies.

50

Jini Surrogate Architecture

l Allows almost any device to participatein Jini federations, including smallJ2ME devices or even non-Javadevices.

l Independent of device type.l Independent of network type.l Preserves Jini Plug and Work

functionality.l Developed as community project at

developer.jini.org/exchange/projects/surrogate/index.shtml

Jini Surrogate Architecture

JiniNetwork

Surrogate Capable Machine

DeviceDevice

Surrogate Host

Host ResourcesHost Resources

InterconnectAdaptor

InterconnectAdaptor

51

Related Technologies

Jini and EJB™

l JiniuDefines a set of protocols for dynamic

federations of servicesuDesigned for dynamic and distributed

environment

l EJBuDefines server-side component modeluDefines hosting environment of

componentsuDesigned for relatively "static" server-

centric environment

52

Jini and CORBA/DCOM

l JiniuJava™ technology centricuCode movement during runtimeuSubtype support

l CORBA/DCOMuCross-language supportuNo code movement

l IntegrationuCORBA/DCOM components can

be wrapped as Jini services

Jini and UPnP

l JiniuCode movement during runtimeuService-centric

l UPnPuNo code movementuDevice-centric

l IntegrationuUPnP devices can be wrapped

as Jini services

53

Jini and OSGi

l OSGiuDefines how smart consumer and small

business appliances can be connectedwith commercial Internet services

l Jini and OSGi are complementaryuJini can provide unified service

framework for OSGi network

Jini and Bluetooth

l BluetoothuOpen standard for wireless proximity

networking communicationuBased on low-cost short-range radio linkuAd-hoc connection among mobile devices

l Jini and BluetoothuFor IP-based Bluetooth devices, Jini

should work with no modificationsuFor non-IP-based Bluetooth devices,

proxy-based Jini services can be built

54

Jini and HAVi

l HAViuStands for Home Audio Video

InteroperabilityuNetwork interoperability of audio and

video devices from multiple vendorsn Transfer of digital contents between

HAVi devices

uJava technology based

l Jini and HAVi integrationuHAVi software modules can be

built as Jini services

Availability and Resources

55

Where are we today?

l 47,000 FCS downloadsl Average 2,000 downloads/monthl 29,000 SCSL Licenseesl 23 Commercial Licensesl Estimated 50,000 active Jini

developersl Four Jini Community meetings to datel 103 Jini Community projects

Jini Partners Include...

Adaptive NetworksAmerica OnlineAxis CommunicationsBEA SystemsBosch SiemensCisco Systems, Inc.Computer AssociatesCreative Design SolutionsDallas SemiconductorPhoenix TechnologiesSony CorporationPalm ComputingInprise Corporation

BullEchelonEncantoFunai Kinkos Corporation Kodak Metrowerks Motorola Novell Nokia Oki Electric Philips

QuantumSamsungSeagateSeikoEpsonCanonSharpSymbian3ComTatungToshibaXerox Corp.

56

Jini TechnologyStarter Kit v1.1

l No changes to the Core.l Focus of release is to add “helper”

utilities and services to aid developersin building Jini clients and services.

l JavaSpaces Technology rolledinto the extended platform (JXP) in thisrelease.

More Information

l Main Sun Jini pageuwww.sun.com/jini

l Jini Communityuwww.jini.org

l Mailing listsuarchives.java.sun.com/archives/jini-

users.htmluarchives.java.sun.com/archives/javaspac

es-users.html

57

More Information

l Jini™ Technology Webcastsu java.sun.com/jdc/onlineTraining/webcasts

l 3rd-party Jini websitesuwww.artima.com/jiniuwww.cdegroot.com/cgi-bin/jiniuwww.kedwards.com/jini/index.htmluwww.litefaden.com/sv/jd/

More Information

l Online tutorialsupandonia.canberra.edu.au/java/jini/tutorial

/Jini.xmluwww.oreilly.com/catalog/jininut/chapter/ch

04.htmluwww.eli.sdsu.edu/courses/spring99/cs696

/notes/index.html

58

Books

For more, please visit:www.sun.com/developers

© Copyright 2000 Sun Microsystems, Inc., All rights reserved.

Sun, Sun Microsystems, the Sun logo, Solaris Operating Environment, Java, Jini, JavaOS,PersonalJava, JavaPhone, JavaTV, EmbeddedJava, Java Card, JDBC, the Java Coffee Cuplogo, JDK, Java virtual machine, JavaCheck, JavaScript, Java Filter, JavaBeans, Java Blend,JavaOS for Consumers, JavaOS for Business, Java Embedded Server, Java DynamicManagement Kit, JavaEngine, 100% Pure Java, HotJava Views, HotJava and The Network IsThe Computer are trademarks, registered trademarks, or service marks of Sun Microsystems,Inc. in the United States and other countries.

All SPARC trademarks are used under license and are trademarks or registered trademarks ofSPARC International, Inc. in the United States and other countries. Products bearing SPARCtrademarks are based upon an architecture developed by Sun Microsystems, Inc.

UNIX is a registered trademark in the United States and other countries, exclusively licensedthrough X/Open Company, Ltd.

59