Copyright 2005 by Codemesh, Inc. All Rights Reserved 1 Welcome Jini and JavaSpaces in an SOA World by Alexander Krapf WebTech Meeting July 19 th, 2005

Copyright 2005 by Codemesh, Inc. All Rights Reserved 1

Welcome

Jini and JavaSpacesin an SOA World

by

Alexander Krapf

WebTech MeetingJuly 19th, 2005


Speaker

Co-founder & President of Codemesh, Inc.

mostly involved with language interoperability

“interested bystander” in Jini and distributed computing


Agenda

What is Jini?

What is JavaSpaces?

How does it compare with Web Services?

Q & A


And the question is…

What is Jini?


Common Misconceptions…

I dream of !Jeannie



Jini is designed for devices

Jini is Java-only

Jini is not ready for primetime

Jini is not supported by Sun


So what is Jini?

Jini is the original SOA

Jini is Java-centric

Jini is more than ready for primetime (just ask Orbitz)

Jini is increasingly better supported by SunStill not part of J2SE platform, now available underApache 2.0 license, small (yet fiercely dedicated) team, small marketing budget


If Jini is one, then what is an SOA?

A system for linking resources on demand. In an SOA, resources are made available to other participants in the network as independent services that are accessed in a standardized way. This provides for more flexible loose coupling of resources than in traditional systems architectures.

An application architecture in which all functions, or services, are defined using a description language and have invokable interfaces that are called to perform business processes. Each interaction is independent of each and every other interaction and the interconnect protocols of the communicating devices (i.e., the infrastructure components that determine the communication system do not affect the interfaces). Because interfaces are platform-independent, a client from any device using any operating system in any language can use the service. Though built on similar principles, SOA is not the same as Web services, which indicates a collection of technologies, such as SOAP and XML. SOA is more than a set of technologies and runs independent of any specific technologies.

Webopedia

whatis.com


Common SOA characteristics…

DeviceIndependent

ProtocolIndependent*

Distributed

Stateless

Scalable

ReliableResilient

Dynamic

Secure

Easy***** to use

Interface-basedLoosely coupled

OS Independent LanguageIndependent


…and how Jini stacks up

Characteristic JiniOS Independence via Java

Language Independence via Codemesh tools, Judy project, …

Device Independence via Java, Surrogates, Psinaptics, …

Protocol Independence RMI is default, protocols easily pluggable

Statelessness yes, by design

Distributed yes, by design

Interface-based yes, by design

Scalable yes, more than anything free I’m aware of!

Resilient yes, more than any other architecture I’m aware of!

Reliable yes, more than any other architecture I’m aware of!

Secure yes, configurable security models (SSL, Kerberos, …)

Dynamic extremely, via Java, RMI, RIO project, …

Easy to use at least for a distributed object technology!


So, really, what is Jini?

the embodied consequence of Jim Waldo et als “A Note on Distributed Computing”

a specification of several core Services providing discovery, transactions, and persistence

comes packaged in a starter kit, not a reference implementation!

based on the acknowledgement that failure is a normal mode of operation!


Jini key concepts

Discovery/Join protocol for bootstrapping

the Service as a discoverable entity the LookupService as the gateway to every other Service

the Lease as a mechanism for resilient Service life-cycle management


A Typical Jini Example

public interface Hello { public String sayHello() throws RemoteException; }

The Hello Service

There is no Service interface that needsto be extended!


A Service Implementation

public class HelloImpl implements Hello { public String sayHello() throws RemoteException { return “Hello!”; } }

The Hello Service Implementation


A Server Implementation

public class HelloServer extends HelloImpl, ServerProxyTrust, ProxyAccessor { public static void main( String[] args ) { Configuration config = ConfigurationProvider.getInstance( args ); Hello serverProxy = (Hello) getExporter( config ).export(this); Proxy smartProxy = Proxy.create(serverProxy); DiscoveryManagement discovery = new LookupDiscovery( null, config ); JoinManager join = new JoinManager( smartProxy, null, getServiceID(), discovery, null, config ); }

... }

The Hello Server Implementation


A Client Implementation

public class HelloClient { public static void main( String[] args ) { Hello server = (Hello)lookup( Hello.class, 10 );

System.out.println( "Server says: " + server.sayHello() ); System.exit( 0 ); }

...}

The Hello Client Implementation

lookup() is ten line boilerplate code!


Important omitted Details…

The Hello client only leased the service

The lease interval defines the application’s reactivity to network failure Lookup can be by type and attribute

What code needs to be deployed on client?


A Typical Jini Example

Client

Lookup Service

Lookup Service

Looking for a Hello service

Lo

okin

g fo

r a Hello

service

“Server”

HelloImplJoin

HelloImplProxy

HelloImplProxy

Dow

nload

Proxy to Impl protocol could be anythingor even nothing! Proxy could just be a dynamically loaded interface implementation!


Jini Example Key Features

Scalability via multiple Service instances

Resilience via multiple Service instances and Lease mechanism

Client only requires service interface, everything else is downloaded dynamically there can but does not have to be a channel between the client and the service

any code downloads or communications can be protected by standard security


What’s missing?

higher-level features related to dynamic deployment, QoS/SLA of Services (RIO project, ServiceContainer project, IncaX, Valaran Inc., etc.)

Inter-Service communications

Distributed data persistence

Workflow/scheduling

JavaSpaces


And the question is…

What is JavaSpaces?



What do we have on the screen there lieutenant?

It must be a JSpace, captain!

j



JavaSpaces is a database

JavaSpaces is slow

JavaSpaces is a research project


So what is JavaSpaces?

JavaSpaces is not a database but it may optionally use one

JavaSpaces is a Jini Service thereby inheriting all Jini advantages

JavaSpaces is … JavaSpaces

a distributed object store/cache

a work orchestration/distribution mechanism

best defined through its use


The usual illustration…

there can be multiple space instances

read, write, take are the most common operations

no modification of entries in space (take out – modify - put back)


JavaSpaces key concepts

Space contains implementations of Entry

Entries are mobile Java objects, not just data! Entries are leased from the space

Entry operations can be transacted

Entries are queried by example


A Computation Server Example

public class Task implements Entry {

public String priority = null; public String jobid = null; public String owner = null; public Boolean done = null;

public void execute() {};}

public class ModelingTask extends Task {

public int[] inputs = null; public int[] outputs = null;

public void execute() { … }}

The interface for all computations

A concrete tasks



JavaSpace space = getSpace();

ModelingTask mt1 = new ModelingTask( “NORMAL”, “job1”, “alex” ); mt1.inputs = new int[] { 10, 20, 30 };

ModelingTask mt2 = new ModelingTask( “NORMAL”, “job1”, “alex” ); mt2.inputs = new int[] { 20, 40, 60, 80 };

space.write( mt1, null, Lease.FOREVER );space.write( mt2, null, Lease.FOREVER );

Client-side: Posting the problem




ModelingTask template = new ModelingTask( null, “job1”, null ); template.done = Boolean.TRUE;

ArrayList results = new ArrayList();long waitUntil = System.currentTimeMillis() + 60 * 1000;

while ( true ) { long maxWait = waitUntil – System.currentTimeMillis();

if( maxWait < 0 ) break;

Entry e = space.take( template, null, maxWait ); results.add( e );}

Client-side: Retrieving the solution




Task template = new Task( null, null, null ); template.done = Boolean.FALSE;

while ( true ) { Transaction txn = createTransaction( 10 * 60 * 1000 ); try { Task t = null; t = (Task)space.take( template, txn, Long.MAX_VALUE ); if( t != null ) { t.execute(); space.write( t, txn, Lease.FOREVER ); txn.commit(); } } catch( Exception e ) { txn.abort(); }}

Server-side: Processing the problem


And Web Services?

Are not nearly as dynamic

Have the “industry standard” advantage

Are becoming less transparent/easy as they get closer to being an SOA Have one big advantage: language independence! (as long as a full protocol stack is available)

Codemesh JunC++ion and JuggerNET


Proxy-Based Solution

What does this look like at runtime?

Java Server

Service

.NET Client

Proxy’

RuntimeLibrary

Service

JVM

Proxy

ProxyProxy’

Client Process Server Process


Proxy-Based Solution

JVM C

JNI

DLL

GeneratedProxy

Classes(C#)

C#

PInvoke

assembly

API

.NETUser

Architectural Diagram


Key Differentiators

Jini provides mobile code capabilities

In Jini, you can choose where the service is run (client or server)

Smart clients are trivially easy to develop and deploy with Jini

Security available without extensions, third-party products


Thank you!

Codemesh, Inc.P.O.Box 620Carlisle, MA 01741

http://[email protected]

Let’s chatand have some drinks!

Documents

Copyright 2005 by Codemesh, Inc. All Rights Reserved 1 Welcome Jini and JavaSpaces in an SOA World by Alexander Krapf WebTech Meeting July 19 th, 2005