JavaSpaces is a powerful Jini service that provides a high-level tool for creating .. In a tutorial style, we cover the mechanics of creating a space-based. Selection from JavaSpaces™ Principles, Patterns, and Practice [Book] access to videos, live online training, learning paths, books, tutorials, and more. If you want more detail, I recommend Jan Newmarch’s Jini Tutorial. A JavaSpace is a Jini service that stores Java objects in memory. This makes it very useful.
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Clients are not impacted by, or even aware of, these operations.
Producer nodes populate the space with some kind of tuple representing partitions of a problem. Building You will need the Jini 2. Image courtesy of Sun Microsystems Those tutoriwl methods suffice to provide the core features most often required in distributed systems: To do so, Jini relies on four core capabilities: Unlike JavaBeans, all of the data members of an Entry must be public.
All resources in a Jini system are leased, including proxy records in the lookup service, transactions, and, of course, memory in a JavaSpace. One feature of Jini worth separate mention is the concept of leasing. Lookup Service The lookup service, named reggieis the first among equals of Jini services.
Introduction to Jini and JavaSpaces | Jini and JavaSpaces: Enabling the Grid | InformIT
Contents of a JavaSpace are associative, meaning that they are addressed searched by their contents instead of a specific location identifier. This prevents resource accretion, a common problem in distributed systems.
Image courtesy of Sun Microsystems The master-worker pattern is used in a wide variety of problem domains where either a problem is highly parallelizable or there are a set of tasks that can be performed by any of a set of workers. The JavaSpaces05 specification adds support for batch operations.
The code to take tasks from the space looks very similar to the SleepMaster for retrieving results: In this version of the pattern, tasks either expose an execute method or include a strategy to configure the generic worker. The Jini programming model extends the core Java classes to include semantics for distributed computing.
In fact, deployment configuration is the most difficult and error prone aspect of Jini, the first time you do it. These javaspace services include service registration and lookup, distributed event notification and messaging, principal and access control list security, and a model for distributed transactions. If we make it a field, it will have the correct behavior.
Jini comes with several standard infrastructure components out of the box. Tutoorial book introduces the JavaSpaces architecture, provides a definitive and comprehensive description of the model, and demonstrates how to use it to develop distributed computing applications.
JavaSpaces is described in a Sun Microsystems specification as part of Jini, and a reference implementation called Outrigger is distributed with the Jini Starter Kit. Deploying Jini Deploying the Jini infrastructure is considerably javsspaces straightforward than building the example.
Consumer nodes take tuples from the space and perform some task, possibly placing results back into the space as different tuples.
Jini technology provides a flexible infrastructure for tutoriaal services in a network and for creating spontaneous interactions between clients that use these services regardless of their hardware or software implementations. Entry is a simple tag interface that does not add any methods but does extend Serializable. JavaSpaces and tuple spaces in general are well-suited to solve problems that avail themselves to blackboard-style solutions or more generally, implementations following the compute-server pattern.
Jini-based systems are described as “network plug and play,” which is a reference to the dynamic, discovery-based nature of interactions between clients and services in a Jini system. The Jini lookup service The Jini transaction manager A JavaSpace The master, a JavaSpace client that writes tasks and reads results The worker, a JavaSpace client that takes tasks and writes results Functionally, the example is uninteresting — the workers just sleep for random periods of time.
This pattern is quite simple: Service implementations can be moved without impacting clients. Please contact me by email if you have any questions, comments, or suggestions.
Jini and JavaSpaces
View table of contents. Hutorial sat back and asked: Leases allow for the dynamic nature of a grid environment, in which services and clients join and leave the system. The workers take tasks at whatever rate they are able to process them, automatically load balancing the work across available resources.
You might think of the blackboard as an implementation of the Mediator pattern, which reduces the coupling between objects.