Transcript Jinitm Architecture - Kent State University

JiniTM Architecture
Source : Sun Microsystems Inc., JiniTM Architecture Specification;
www.sun.com/jini/specs/jini1_2.pdf
JiniTM – A Technology for interconnecting heterogeneous
devices; Lauri Eronen University of Helsinki, Department of Computer
Science
California Software Laboratories, Jini by example - Whitepaper;
www.cswl.com/whitepaper/tutorials/jini.html
Sun Microsystems Inc., JiniTM Connection Technology Architecture
Overview by Bill Day
Presented by Mark Miyashita
04-08-2002
Topics
• Who developed Jini?
• Why Jini?
• What are the Goals, benefits, and Limitations?
• What is Jini?
• Jini Architecture Overview
• Related technology
Who developed Jini?
• Jim Waldo (COBRA, RMI, JavaSpaces)
• Bill Joy (BSD Unix, SunOS)
• Ken Arnold (JavaSpaces)
• Bob Sheifler (X Window Systems)
In addition, many developers and partners
involved in developing and assist in maturing
Jini technology
Why Jini?
Distributed computing is more difficult than local
computing because of:
• Network Latency
• Concurrency issues
• Memory Management
• Inevitable partial failure
Goals of Jini
• Enabling users to share services and resources
over a network
• Providing users easy access to resources
anywhere on the network while allowing the
network location of the user to change
• Simplifying the task of building, maintaining,
and altering a network of devices, software, and
users
Benefits (value) of Jini
• Makes using a network more like using a phone
(plugging in networked devices and application
software is as simple as plugging in a phone)
• Simplifies adding and management of application
services easier
• Simplifies the task of writing distributed
application by freeing programmers from worrying
about underlying network topology
Limitations of Jini
• Scalability – intended for less than 1,000
resources
• Requires Java 2 Platform, 48KB of memory –
Jini’s Java-dependency, require too much
processing power and memory for most devices
(new Jini device architecture Specification address
this issue)
• Many standardized interfaces for Jini services are
under development (Jini Printer Working group,
Jini Storage Working Group, see www.jini.org)
What is Jini Technology?
• An infrastructure to federate services in a
distributed system
• Jini enables spontaneous networks of software
services and devices to assemble into working
groups of objects, or federation
• Simplify delivery and access of network services
• Jini addresses the problem of distributed
computing using a set of simple interfaces and
protocols
What is Jini Technology?
• Adapting to the changing nature of the network
and mobility of devices and services
• Jini provides simple mechanisms which enables
devices and services to be removed/added to the
federation
• Everything is represented by Java objects
• Everything is located and accessed through Java
interfaces
Key Concepts
• Services
• Lookup Services
• Discovery and Join protocols
• Java Remote Method Invocation (RMI)
• Security
• Leasing
• Transaction
• Distributed Events
Jini Architecture Overview
Jini Service
Jini
infrastructure
Application Service
Lookup
Discovery/Join
RMI
Operating System
Network Transport
• Java VM and RMI is the basis for Jini infrastructure.
• Java VM and portable object code provides benefit of
homogeneous network and architecture independence
Components of a Jini System
• Jini extends the Java Platform
Divided into three categories:
• Infrastructure – set of components that enables
building a federated Jini system (defines the
minimal Jini code)
• Services – actual services constructed using Jini
(entities within the federation)
• Programming Model – set of interfaces that
enables the construction of reliable services
including the services belonging as part of the
infrastructure as well as actual services
Components of a Jini System
Infrastructure
Programming
Model
Services
Base Java VM
Java RMI
Java Security
Java API
JavaBeans
Swing
JNDI
JTS
Enterprise
Beans
Java
+
Jini
Leasing
Events
Transaction
Printing
Transaction
Manager
Other
services
Discovery/Join
Lookup
Distributed
security
Jini Infrastructure –
Jini Lookup Service
•Repository of available services
•Stores each service as Java objects
•Clients download services on demand
•Lookup service provides mapping: interfaces to
objects
•Lookup service may include entry for other lookup
services (federated with other lookup services)
•Lookup service interface provides: registration,
access, search, removal
Jini Infrastructure –
Jini Lookup Service
• In short, Jini Lookup service is about finding
service in the federation by the client
• To find a service, a Jini client locates appropriate
service by querying a lookup service by type (Java
interface)
• Code moves from service to client via lookup
service
• Code needed to use service is dynamically loaded
into client on demand
Jini Infrastructure –
Discovery/Join protocol
• Discovery and join occur when device is plugged
in (pair of protocol used to find and join a group
of services)
• Discovery occurs when a service provider is
looking for a lookup service with which to register
• Join occurs when a service has located a lookup
service and wishes to join it
• Jini discovery/join is the process of adding a
service to a Jini system
Jini Infrastructure –
Discovery/Join protocol
• A service provider is the originator of the
service – software or hardware
• Based on UDP multicast – service provider
locates a lookup service by multicasting a request
on the local network for any lookup services
• Provide required software drivers and its
capabilities – service object (proxy) for the
service is loaded into the lookup service
• Service object (proxy) contains the Java
programming language interface for the service,
including the methods that users and application
will invoke to execute the service
Jini Infrastructure –
Discovery/Join protocol
• Along with service objects, descriptive service
attributes (service capability) gets loaded into
lookup service during the join phase
• In short, discovery/join protocol establish
references with lookup service
• Unicast discovery also supported
Jini Infrastructure –
Java RMI
• Java Remote Method Invocation (RMI)
mechanism is a fundamental for Jini
• RMI is an Java language based extension to
traditional remote procedure call mechanism
• Passing both remote object references (pass-byreference) and actual object (pass-by-value) as
method parameters are possible
• RMI allows not only data to be passed from
object to object around network but also, full
objects including executable code to be move
around in a network
Jini Infrastructure –
Java RMI
• Communication among services uses Java RMI
• RMI provides
• Activation – Java objects that provides
services need not be running all the time (it can
be activated by RMI when a request for the
service arrives)
• garbage collection
• multicast
Jini Infrastructure –
Distributed Security
• A distributed security system that extends the
basic Java security model (JVM protects the client
from malicious downloaded code that could cause
damage)
• Principal – Jini services are accessed on behalf of
some entity which generally traces back to a
particular user of the system
• Access control list – Associates access privileges
with each object implementing a service (service
may request access to other service based on the
identity of the object that implements the service)
Jini Infrastructure –
Discovery protocol
Lookup Service LUS
Lookup Service LUS
Service provider
seeks LUS
Client
Lookup Service LUS
UDP
Multicast
Service Provider
Service Object
Service Attribute
Jini Infrastructure –
Join protocol
Lookup Service
Service Object
Service Attribute
Client
A service provider registers a
service object (proxy) and its
service attributes with the
lookup service (joins a
federation) for other clients and
services to use
Service Provider
Service Object
Service Attribute
Jini Infrastructure –
Lookup Service
Client Requests a service
by type (java interfaces)
and/or service attributes.
A copy of the service
object is moved to the
client to talk to the
service provider
Client
Service Object
Lookup Service
Service Object
Service Attribute
Service Provider
Jini Infrastructure –
Using Service
• All communication happens between the client
and the service through service object (proxy)
• Independent of wire protocol – the method of
communication between the client and the service
is not specified in the Jini architecture
• The actual communication method is determined
by the service provider, who provides service
object (proxy) that implements that interface
• Protocol can change without affecting client
• RMI semantics is core to functionality – it can use
any other communication method
Jini Infrastructure –
Using Service
•The client interacts directly
with the service provider via
the service object (proxy)
• Lookup service is no
longer involved
Client
Service Object
Lookup Service
Service Object
Service Attribute
Service Provider
Example –
Jini Enabled Printer
GUI
Drivers
Jini Infrastructure
Java VM
Example –
Discovery
Multicast query for
Lookup service
UDP Multicast
Example –
Discovery
Lookup service
discovered
LUS
Example –
Join
Printer registers
service object
(proxy) with LUS
LUS
Example –
Lookup
Client search LUS
for Printer
Printer ?
LUS
Example –
Lookup
LUS returns
printer service to
client
LUS
Example –
Using services
Client communicates to
printer through service
object (any protocol)
LUS
Programming Model –
distributed leasing
• Problem : Partial failure in distributed systems
can lead to unchecked resource consumption
• An access to services in Jini is lease based
• A lease is a grant of access over a time period
(protocol for managing resources using a
renewable, duration based model)
• Each lease is negotiated (contracted) between the
user of the service and the provider as part of this
protocol
• Leases are either exclusive or non-exclusive
(service can not be shared)
Programming Model –
distributed leasing
• If lease expires without renewal, user and provider
can free up associated resources
• Leases handle client and network failure, removal of
services (leases may be cancelled, renewed, allowed to
expire)
• Resources are allocated only as long as continued
interest is shown by leasee (leasee’s responsibility to
renew lease before expires)
• Used also in LUS to keep the list of available service
up to date (service provider must renew the lease)
• In short, lease provides a method of managing
resources in a environment where failure can occur
Programming Model –
distributed Events
• Jini extends standard Java event mechanism to
work in a distributed network
• Register interest, receive notification (an object
may allow other object to register interest in the
object and receive a notification of the occurrence
of such an event
• Use RMI and distributed leasing protocol
• In LUS, delivering to the LUS information about
state changes of services registered to the LUS
Programming model –
Transaction
• Jini includes interfaces that define the
functionality needed for performing a two-phase
commit (Jini specification does not dictate the
semantics for the concept of transaction, only
interfaces are provided)
• Transaction interface introduce a lightweight,
object oriented protocol enabling applications to
coordinate state changes (designed for distributed
object coordination)
Services
• Infrastructure and programming model are built
to enable services to be offered and found in
network federation
• Service may be added or removed from a
federation at any time
• Provides mechanism for service registration,
lookup, and use
• Services represented (defined) by Java interfaces
– implementation can change over time without
effecting infrastructure or clients
Services are defined by
Java interfaces
I’m a printer
Interface
printer
I’m a color
printer
Interface
Color
Printer
Client finds service by
interface
Client
Give me a Printer
Interface printer
Interface Color printer
LUS
Jini and CORBRA/DCOM
• Jini
• Java technology centric
• Code movement during runtime
• COBRA/DCOM
• Cross language support
• No code movement
• Integration
• COBRA/DCOM components can be wrapped as
Jini services
Jini and UPnP
• Jini
• Code movement during runtime
• Service centric
• UPnP
• No code movement
• Device centric
• Integration
• UPnP devices can be wrapped as Jini services
Jini and Bluetooth
• Bluetooth
• Open standard for wireless proximity
networking communication
• Based on low cost, short range radio link
• Ad-hoc connection among mobile devices
• Jini and Bluetooth
• For IP-based Bluetooth devices, Jini should
work without modifications
• For non-IP-based Bluetooth devices, proxybased Jini services can be built