October 10, 2007
Grid-Enabling Resource-Intensive ApplicationsDistribution Strategies
There are two different basic ways to distribute the jobs to the worker machines in this type of consumer-producer scenario (Table 3). These are known as the "push model" and the "pull model." The way we will describe these is to have a "Master" computer, which is the controller, and many "Worker" computers that merely share their resources and perform computations. This is commonly known as the Master-Worker Paradigm (see Figure 2). The Master initiates the computation by creating a set of tasks or jobs. With the push model, the Master divides up the jobs by some predefined criteria and sends them to the Workers. With the pull model, the Master puts the jobs in some shared container and then waits for the tasks to be picked up and completed by the Workers (see Figure 3).
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Figure 2: CodeGrid master worker paradigm.
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Figure 3: CodeGrid work distribution.
Table 3: Distribution strategies.
One of the advantages of using the pull model is that the algorithm automatically balances the load. This is due to the simple fact that the set of work is shared, and the workers can pull work from the set at their own pace until there is no more work to be done. The pull model provides excellent load balancing regardless of Worker speeds and network variations. This algorithm also has good scalability. Frameworks
The three frameworks (see Table 4) we considered in the development of this software were:
Table 4: Frameworks.
In consideration of timeliness and saving costs associated with writing and debugging code, it is often advantageous to utilize as much existing code as possible in creating an application. Open source and vendor supplied code snippets can perform many common functions such as standard I/O socket management. This is one area where Java really excels and there are many of these snippets (known as "JavaBeans") downloadable from both Sun and associated vendor's websites.
.NET is similar to the Java solution in that it provides libraries of coded solutions to common program requirements and manages the execution of programs written specifically for the framework. The ideal language to use for this project with .NET would be C#, which is based on Java and C++.
The drawbacks of using .NET for this project were:
Java Native Interface (JNI) is a programming framework that lets Java code running in the Java VM call and be called by native applications and libraries written in other languages, such as C, C++, and assembly. The JNI can be used to wrap an existing application (such as CodeMatch), written in another programming language (in this case, C), and enable its functions to be accessible to Java applications. The main advantage of this tool is that legacy application code can be integrated with new Java code and not have to be rewritten in Java. The main drawbacks of using JNI are:
JavaBeans are simply software components written in Java that have a standard format that makes them ideal for reuse in many different projects. JavaBeans are also independent objects that can exist outside of a program. JavaBeans are intended to handle common functions leaving you free to concentrate on the particular program at hand. Enterprise Java Beans (EJBs) let highly scalable, platform independent, complex systems be built quickly and cost effectively. The main drawback of using EJBs is that the API is very complicated with many interfaces to implement, and many complex XML deployment descriptors.
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1 Grid-Enabling Resource-Intensive Applications
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2 Architectures and Communication Strategies
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3 Distribution Strategies
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4 Conclusion
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