jini design and principles ranjita bhagwan cse225: high-performance distributed computing

JINI Design and Principles

Ranjita Bhagwan

CSE225: High-Performance Distributed Computing

What is Jini?

• A distributed computing environment for Network Plug and Play.

• A system to provide services easily and transparently over the network.

• A system that can be “dynamic” - users and resources can come and go as they please with minimal administrative overhead.

Jini’s goals

• Provide shared service and resources.• Provide easy access to resources in spite of

changing network location of users.• Simplifying system and network

management.• Not yet a platform for a parallel programming

environment – more of a “plug and play” mechanism than a metacomputing infrastructure.

Jini Architecture

Infrastructure Programming Model

Services

Base Java

Java VM JAVA APIs JNDI

RMI JavaBeans Enterprise Beans

Java Security … …

Java + Jini Discovery/Join Leasing Printing

LookupTransactions Transaction

Manager

Distributed Security

Events …

Jini Components

• Service – an entity used by a person, program or another service.

• Service Locator/Lookup Service – keeps track of services and their properties and provides the Lookup Service.

• Client – uses the services.

ClientServiceLocator

Service

Service

• An object (or set of objects) located in a server which can be used by a user, program or another service.

• An application can be viewed as a collection of services – different from regular object-oriented view.

• More localized notion than Globus service, which can be distributed over a number of hosts.

Small Example

SmartViewergetMIMEType()

FileClassifier

display()

DisplayService

display()

ImageDisplay TextDisplay

display()

Example

FileClassifierProxy

ImageDisplayProxy

TextDisplayProxy

Service locator

SmartViewer

FileClassifierProxy

ImageDisplayProxy

FileClassifierService

TextDisplayService

ImageDisplayService

Service

Service

Service

User

Lookup Service

• Service is added to the Lookup Service by a pair of protocols– Discovery: Service locates the lookup service.– Join: Service joins the lookup service.

• Server “discovers” the service locator– Unicast TCP if location of service locator is known.– Multicast UDP if location of service locator is not

known.

• May include other Lookup Services for hierarchical lookup.

Discovery/Join & Lookup

Service Registration

Service Locator Service Server

service

registrarservice

Object Serialization is used to move the service object to the Service Locator.


Client Lookup

Client Service Locator

serviceregistrarregistrar

service

Object Deserialization is used at the client torecreate the object.


Entries and Groups

• Entries: A service may specify certain properties.– For a plain text editor, entries = {(“plain/text”)}– A client may specify the properties it requires of the

service.– A matching of all specified entry fields is performed

with the services on the service locator. – Relational operators (>,<, etc) not supported!– Serialized entries are compared.

• Groups: A service can specify which groups it belongs to. – Groups = {“CSE, UCSD”, “ECE, UCSD”)


Service Proxies• Toaster, Printer, etc. cannot

perform their services remotely.• So, service sends out a “proxy”.• The proxy communicates with

the service.• The proxy is told its server’s

location when it is created.

ClientServiceLocator Service

Service Proxy

Registrar

Service Proxy

Registrar

Service


Jini Architecture


Services

Base Java






Manager


Events …

Leasing: request and grant

• The service requests that its copy be kept on the service locator for a given amount of time.– ANY: service locator determines lease time.– FOREVER: request for a lease that never expires.

• The service locator grants the lease and specifies how long it stays valid.– Default for SUN = 5 seconds.

Leasing

Leasing: Expiry

• “Quiet” expiration: no notification from the service locator to the service.

• The service has to renew the lease before it expires.– Problem: high network latency may cause

lease to expire before it is renewed.

• The Lease Renewal Manager quietly renews leases at regular intervals.

Leasing

Jini Architecture


Services

Base Java






Manager


Events …

Security

• Based on JDK 1.2 security model.

• Uses a text based policy file to set security policy.

• If an all permissive policy is used, a malicious service, masquerading as a requested service may run on the client.

Security

JDK 1.2 Security

• Grant permission only for certain activities, such as access to certain files for reading, writing and execution.

• Grant access only to particular hosts, subdomains or domains.

• Require digital signatures attached to code.

Security

Security problems for a client

service locator

http server

service proxyinstance data

proxy class files

Security

client

A Policy that restricts attacks

Grant permissions to Application code based on the codesource. If you suspect these might be tampered with, get them signed.

Security


Grant permission to Jini core classes based on the codesource. These may be signed if need be.

Security


Grant permission to downloaded code only if it is signed by an authority you trust. Even then, grant only the minimum permission that is needed to perform the service’s task.

Security

Security challenges

• security should be strong but easily managed so that the ease of use of Jini does not disappear.

• In ad-hoc networks, when services may not have a fixed identity, how do you decide who is “trusted” and who is not?

Security

Jini Architecture


Services

Base Java






Manager


Events …

Transactions

• A series of operations within a single service or involving multiple services.

• ACID properties– Atomicity– Consistency– Isolation– Durability

• Jini uses the two-phase commit method.

Transactions

Two-phase commit

• Mechanism– All participants in a transaction “vote” on it. – If all agree to go ahead, transaction

commits.– If any of them abort during the voting

stage, the transaction aborts on all participants.

• Jini supplies the mechanism, but policies are left to the participants.

Transactions

An example

client service accounts txnmanager

get cost

Transactions

An example


cost

Transactions

An example


create

Transactions

An example


txn

Transactions

An example


credit

txn

Transactions

An example


credit debit

txn

Transactions

An example


join

txn

Transactions

An example


txn

request service

Transactions

An example


txn

result

Transactions

An example


txn

commit

Transactions

An example


txn

prepare

Transactions

An example


txn

commit

Transactions

Related Technologies

• HAVi

• JetSend by Hewlett-Packard

• Bluetooth

• Inferno by Lucent

• Universal Plug and Play

“Sun officials this morning said Universal Plug and Play is behind Jini in development terms, and criticized it for being "PC-centric" and thus tied to the Microsoft operating system. Microsoft has countered that for Jini to work, thousands of applications will have to be rewritten in Java and Jini code.”

JINI v/s UPnP

Non-technical Issues

• July 1998: Jini was introduced.– “Jini products will be out by mid 1999.”

• Jan 1999: Around 30 partners to the Jini technology were announced.– “Jini products will be out by late1999.”

• Are they out yet?

Jini Products

• It is claimed that e-commerce and web-based applications are overshadowing Jini product development.

• Jini product prototypes are being developed by a number of companies – HP, 3Com, Cisco, Sony, Nokia, etc.

Concerns• Security!!!• Common interface development

– All printers should ideally use the same interface.

• Does not as yet support XML, which UPnP does(will do).• Needs JAVA VM to run on every device to avoid large

delays: this means large memory requirements.– Possible solution: Dallas semiconductors’ JAVA VM on a chip.

• Needs all applications to be coded in Java.– All manufacturers have to accept Java as their programming

language.• Scalability issues

jini design and principles ranjita bhagwan cse225: high-performance distributed computing

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