Chapter 15. Distributed Execution

Red Hat JBoss Data Grid provides distributed execution through a standard JDK ExecutorService interface. Tasks submitted for execution are executed on an entire cluster of JBoss Data Grid nodes, rather than being executed in a local JVM.
JBoss Data Grid's distributed task executors can use data from JBoss Data Grid cache nodes as input for execution tasks. As a result, there is no need to configure the cache store for intermediate or final results. As input data in JBoss Data Grid is already load balanced, tasks are also automatically balanced, therefore there is no need to explicitly assign tasks to specific nodes.
In JBoss Data Grid's distributed execution framework:
  • Each DistributedExecutorService is bound to a single cache. Tasks submitted have access to key/value pairs from that particular cache if the task submitted is an instance of DistributedCallable.
  • Every Callable, Runnable, and/or DistributedCallable submitted must be either Serializable or Externalizable, in order to prevent task migration to other nodes each time one of these tasks is performed. The value returned from a Callable must also be Serializable or Externalizable.
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15.1. DistributedCallable API

The DistributedCallable interface is a subtype of the existing Callable from java.util.concurrent.package, and can be executed in a remote JVM and receive input from Red Hat JBoss Data Grid. The DistributedCallable interface is used to facilitate tasks that require access to JBoss Data Grid cache data.
When using the DistributedCallable API to execute a task, the task's main algorithm remains unchanged, however the input source is changed.
Users who have already implemented Callable interface to describe task units must extend DistributedCallable and use keys from JBoss Data Grid execution environment as input for the task.

Example 15.1. Using the DistributedCallable API

public interface DistributedCallable<K, V, T> extends Callable<T> {
 
   /**
    * Invoked by execution environment after DistributedCallable
    * has been migrated for execution to a specific Infinispan node.
    *
    * @param cache
    *           cache whose keys are used as input data for this
    *           DistributedCallable task
    * @param inputKeys
    *           keys used as input for this DistributedCallable task
    */
   public void setEnvironment(Cache<K, V> cache, Set<K> inputKeys);
 
}
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