JINI Technology


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Technology based on JAVA for distributed computting

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JINI Technology

  2. 2. Introduction to JINI • Jini is a way to do distributed computing that helps you manage the dynamic nature of networks. • Provides mechanisms to enable smooth adding, removal, and finding of devices and services on the network. • Provides a programming model for reliable, secure distributed services and makes it easier for programmers to get their devices talking to each other. • Jini technology promises to be a reality in the immediate future as an architecture to enable connections between devices any time, anywhere.
  3. 3. Why Jini technology? • • • • • • Today devices are unaware of their surroundings. They are rigid and they can not adapt. We expend a lot of efforts to install it. We need an expert to do it for us. In JINI, No system administrator required. Everything on the network (hardware or software) is a "service“. • Each service represented by a mobile object.
  4. 4. Working Model • The Java programming language is the key to making Jini technology work. Built on top of Java, object serialization, and Java Remote Method Invocation (RMI), it enables objects to move around the network from virtual machine to virtual machine. Jini attempts to extend the benefits of objectoriented programming to the network. • Jini is written in pure Java but the clients and the services are not constrained to be in Java.
  5. 5. How Jini works? (Process) • To use a service, a person or a program locates the service using the lookup service. • The service's interface is copied from the lookup service to the requesting device where it will be used. • The lookup service acts as a switchboard to connect a client looking for a service with that service. • Once the connection is made, the lookup service is not involved in any of the resulting interactions between that client and that service. 5
  6. 6. Where it can be placed? 6
  7. 7. Architectural Overview • The whole technology can be segmented into : – Infrastructure – Programming Model – Services
  8. 8. Infrastructure • Set of components, includes the minimal JINI technology core, that enables building of the system.
  9. 9. Lookup Service • Central storage of services available within the system • It is the fundamental part of the infrastructure. • It organizes services into groups. – Service can be a member of multiple groups. – Multiple Lookup Services can maintain the same group. – This helps to achieve fault tolerance.
  10. 10. How things work (Service Side)? • When a new service is created, it register itself with a Lookup Service (Join). • It must first locate the appropriate Lookup service (Discovery). • This done using the Discovery/Join Protocol.
  11. 11. How things work (Client Side)? • Client locate the appropriate Lookup Service (Discovery). • It locates a service by querying the Lookup Service (Lookup) • This done using the Discovery/Lookup Protocol. • Then, Client and service can communicate directly.
  12. 12. Discovery Protocol • It can be : – Multicast Discovery Protocol. (looking for an appropriate Lookup Service) – Unicast Discovery Protocol. (looking for a specific Lookup Service or non-local Lookup service) – Multicast Announcement Protocol. (Allow Lookup services to advertise their presence)
  13. 13. Multicast Request Protocol
  14. 14. Unicast Discovery Protocol
  15. 15. Multicast Announcement Protocol
  16. 16. Join Protocol • A service discovers the appropriate Lookup Service. • It connects via the Lookup Service registrar. • The Service sends some info about itself. • The Lookup Service stores the information and associate it with the requested group, if any.
  17. 17. Join Protocol
  18. 18. Lookup Protocol • A Client discovers the appropriate Lookup Service. • It’ll query for the service. • If found, the object reference of the requested service will be loaded into the client. • Finally, client invoke the service.
  19. 19. Lookup Protocol
  20. 20. Distributed Security System • Define how entities got the right to perform actions on their behalf or on behalf of others. • It extends JDK1.2 platform’s security model to the world of distributed systems.
  21. 21. Leasing • Access to many of the services in the Jini system environment is lease based. A lease is a grant of guaranteed access over a time period. Each lease is negotiated between the user of the service and the provider of the service as part of the service protocol: A service is requested for some period; access is granted for some period, presumably taking the request period into account. If a lease is not renewed before it is freed--either because the resource is no longer needed, the client or network fails, or the lease is not permitted to be renewed-then both the user and the provider of the resource may conclude that the resource can be freed.
  22. 22. AR.2.1.6 Transactions • A series of operations, either within a single service or spanning multiple services, can be wrapped in a transaction. The Jini transaction interfaces supply a service protocol needed to coordinate a two-phase commit. How transactions are implemented--and indeed, the very semantics of the notion of a transaction--is left up to the service using those interfaces.
  23. 23. • AR.2.1.7 Events • The Jini architecture supports distributed events. An object may allow other objects to register interest in events in the object and receive a notification of the occurrence of such an event. This enables distributed eventbased programs to be written with a variety of reliability and scalability guarantees.
  24. 24. Programming Model • Set of interfaces that enables the construction of reliable services. • These interfaces make up the distributed extension of Java. • All interfaces are written in Java • Free source code. • Has no limit, and it can be extended.
  25. 25. Programming Model Cont.. • These interfaces include : – Leasing interface – Events interface – Transaction interface
  26. 26. Leasing interface • Access to many services in the JINI system is lease based. • Lease grant guaranteed access to the service over a period of time. • It is negotiable. • Can be exclusive or non-exclusive. • Can be renewed.
  27. 27. Example • When a service registers with the lookup service, it receives a lease. • It need to renew periodically. • When service failed or lease get expired, service will be removed.
  28. 28. Distributed Events Interface • It extends JavaBeans Event Model to the world of Distributed Systems. • One object, Event Listener, registers an interest in event of another object, Event Generator. • Listener will be notified in a timely and reliable fashion. • Registration of interest is lease based
  29. 29. Transaction Interface • Transactions enables operation grouping. Either all Succeed or all Fail. • The JINI’s Transaction Interface supply a service protocol needed to coordinate 2Phase commit protocol.
  30. 30. Service • Something that can be used by a person, program or another service. • It can be : Computational, Storage, Software, Hardware or Communication Channel. • It has an interface which define the operations that can be requested.
  31. 31. Services Cont.. • Service objects can be written in any language. Client does not care. • But the interface has to be written in Java. • One of them is JavaSpaces which can be used for simple communication and storage of related groups of objects.
  32. 32. Example
  33. 33. Advantages • We no longer need a computer to act as an intermediary between a cell phone and a printer • These devices can take care of themselves-they are flexible, they adapt • Self configure • Self diagnose • Self install • Reduce need for expert help • Lower total cost 33
  34. 34. Disadvantages • Communication overhead, so some time it’s slow • High Learning curve and some cost involve 34
  35. 35. Conclusion • JINI is the feature of distributed systems. • The dynamic nature of JINI allows resources to be added, subtracted at anytime without bothering other components. • Open Source Code is available for download. Thus it has no limit.
  36. 36. References • The main JINI page at Sun: http://java.sun.com/products/jini/ • JINI specifications: http://java.sun.com/products/jini/specs/ • JINI-USERS mailing list archives: http://archives.java.sun.com/archives/jini-users.html • Bill Venners' JINI/JavaSpaces talk: http://www.artima.com/javaseminars/modules/JINI/ Handout.html • JINI Community Web Site, devoted to JINI http://www.jinivision.com