Distributed Systems with JINI

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Distributed Systems with JINI

• Lincoln Carlton
• 4/23/01
• Parallel and Distributed Systems

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What is JINI?

• No one really know what JINI really stands for.
  (Anyone know what JAVA stands for?)
• JINI is a distributed system based on groups of
  Federated users and resources required by those
  users.
• Overall goal is to provide a flexible, easily
  administered tool on which resources can found
  and shared.
• JINI extends the JAVA environment from a single
  Virtual Machine to a network of VMs, with both
  code and data moving between machines.
• Built in security of JAVA platform to allow code
  to be built on one machine, executed in another
• Strong typing to the class level
• Allows services to Discover, Join, Detach
  dynamically from a JINI system.

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Why JINI?

• Todays N-tier network systems (like DCOM, CORBA
  or RMI) require that components
• know about each other while they are being built
• Be evolved lock-step, because interface changes
  require global synchronization
• Require fairly tight administration
• Seven Fallacies of Networking
• The network is reliable
• Latency is zero
• Bandwidth is secure
• Network is secure
• Topology doesnt change
• There is one administrator
• Transport cost is zero

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Why JINI?

• Move from a N-tier system to a P2P system.
• The scale of interactions between peers increases
  if everyone can communicate with everyone else
• The rate of exchange increases
• Napster scenario, no one-entity can control the
  exchange of services
• JINI absolves some of the networking fallacies
• Deals with the unreliability of the network (1)
• Keep up with changing Topology(5)
• Allow multiple administratorsor none!! (6)
• Evolve Components
• Take failure seriously and recover from it (Self
  Healing Networks)

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A JINI system is composed of...

• A set of components that providing an
  infrastructure for federating services in a
  distributed system
• A programming model that encourages production of
  reliable distributed services
• Services that can be federated to offer
  functionality to other members of the federation
• The Overall Goal
• Enable users to share services and resources over
  a network
• Provide users easy access to resources over a
  network while allowing the user to change network
  locations
• Simplify the task of building, maintaining and
  altering a network of devices, software and users.

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Key Concepts

• Services
• Any entity that can be used by a program, user or
  another service. Examples include printing a
  document or translating a document from one
  word-processor format to another.
• Lookup Service
• Services are found using a lookup. Employs a
  hierarchical mechanism to allow services to
  contain lookup services.
• RMI
• An RPC mechanism that pioneered the ability to
  move JAVA object from one VM to another. Used by
  JINI to find and communicate with objects.
• Security
• Two ideas dominate JINI security
• a principal Usually a user of the system who is
  authenticated
• an access control list lists principals or
  groups of principals allow to access an object

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Key Concepts

• Leasing
• All service access in JINI is based on a lease.
  The access is granted for a timed-interval.
  Leases can be exclusive or non-exclusive
• Transactions
• Actions in any number of services may be
  collected into a single transaction. Two-phase
  commit ensure that all service action are
  committed or rolled-back together.
• Events
• Distributed events allow asynchronous
  notification between objects with reliability,
  scalability and interval guarantees.

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Component Overview

• Infrastructure
• What is provided by the JINI system to make it
  work?
• Programming Model
• What interfaces must be created to integrate with
  the JINI system?
• Services
• Combining Infrastructure and Programming Model,
  create a service for federating device.

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Infrastructure

• Three components compose the base of the JINI
  system
• Distributed Security enforcing the Principal and
  ACL security devices across the network
• Discovery/Join protocol to allow service to
  discover, join and advertise their functionality.
• Lookup Service service as a repository of services

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Programming Model

• A service must implement base JINI interfaces to
  integrate with the JINI system
• Leasing interface ensure accurate set of
  services are listed
• Event and notification interfaces JavaBeans
  based notification models
• Transaction interfaces Voting phase, commit
  request
• In addition, the service must implement desired
  functionality (i.e. the Printing service)

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Services

• The JINI infrastructure, defined by the JINI
  specification, provides the means of sharing code
  and data between VMs.
• The implementation of the Leasing, Event and
  Transaction interfaces allows service integration
  in the federation.
• A Service provides the value-add in the system.
  For example a printing service, light-switch
  service, PDA synchronizing service.
• So how does it all fit together?

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Service Architecture

• Three protocols
• Discovery happens when a service is looking for a
  lookup service to register with.
• Join happens when a lookup service is found and a
  service is added to the federation.
• Lookup happens when a client or user needs to
  locate and invoke a service..

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Discovery
Lookup Service
Service
Client
Service Object
Service Attributes
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Join
Lookup Service
Service Object
Service Attributes
Service
Client
Service Object
Service Attributes
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Lookup
Lookup Service
Service Object
Service Attributes
Service
Client
Service Object
Service Attributes
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Lookup
Lookup Service
Service Attributes
Service
Client
Service Object
Service Object
Service Attributes
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Service Invocation
Lookup Service
Service Attributes
Service
Client
Service Object
Service Object
Service Attributes
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Example Registering and Using a Printer Service
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Code Examples
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More Information

• Core JINI by Keith Edwards
• Various Whitepapers at http//java.sun.com
• Questions