3.5. Job dependencies on system environment

As shown earlier, a grid application does not require a homogenous runtime environment, but there are certain considerations to be made in order to plan for the most beneficial deployment of it.

For any job in a grid application the following environmental factors may affect its operation. When developing an application, one must consider these factors and either design it to be as independent of these factors as possible, or understand that any dependencies will need to be taken into account within the grid infrastructure.

• Operating Systems version, service level, and OS parameter settings that are necessary for execution of the job, as well its reliance on certain system services and auxiliary programs such as a registry. It is worthwhile to consider whether the grid application will be capable of running its jobs on any node with different operating systems or whether it will be restricted to a single operating system.

• Memory size required by a job may limit the possible nodes on which it can run. The available memory size depends not only on its physical presence at a node, but also on how much the operating system is capable of granting at run-time.

• DLLs that are to be linked for the execution of the job. They either need to be available on the target resource or could possibly be transferred and made available on the resource before the job is executed.

• Compiler settings play a role as compiler flags and locations may be different. For example, subtle differences like bit ordering, and number of bytes used for real and integer numbers may cause failures when a job is compiled on a different node or operating system than the one it will eventually be executed on.

• Runtime environment that has to be in place and ready to receive the job for execution. For instance, the right JDK or interpreter versions may have to be planned and in place.

• Application Server version and standard as well as its capacity may be needed to be considered as well as access requirements and services to be used.

• Other applications that are needed to properly run a job have to be in place prior to deployment of the grid application. These applications can be compilers, databases, system services such as the registry under Windows, and so on.

• Hardware devices that are required for certain jobs to perform their tasks. For example, requirements for storage, measurement devices, and other peripherals must be considered when building the application and planning the grid architecture.

When developing the grid application, these prerequisites need to be checked in order to avoid too many restrictions for job execution. A large number of restrictions could mean more complicated enablement as well as limiting the number of possible nodes on which the job will be able to run. Therefore, it is better to restrict such requirements during development of the application such that jobs can run in as generic an environment as possible.