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16.4. Distributed Task Failover
Red Hat JBoss Data Grid's distributed execution framework supports task failover in the following cases:
- Failover due to a node failure where a task is executing.
- Failover due to a task failure; for example, if a
Callabletask throws an exception.
The failover policy is disabled by default, and
Runnable, Callable, and DistributedCallable tasks fail without invoking any failover mechanism.
JBoss Data Grid provides a random node failover policy, which will attempt to execute a part of a
Distributed task on another random node if one is available.
A random failover execution policy can be specified using the following as an example:
Example 16.3. Random Failover Execution Policy
DistributedExecutorService des = new DefaultExecutorService(cache); DistributedTaskBuilder<Boolean> taskBuilder = des.createDistributedTaskBuilder(new SomeCallable()); taskBuilder.failoverPolicy(DefaultExecutorService.RANDOM_NODE_FAILOVER); DistributedTask<Boolean> distributedTask = taskBuilder.build(); Future<Boolean> future = des.submit(distributedTask); Boolean r = future.get();
The
DistributedTaskFailoverPolicy interface can also be implemented to provide failover management.
Example 16.4. Distributed Task Failover Policy Interface
/**
* DistributedTaskFailoverPolicy allows pluggable fail over target selection for a failed remotely
* executed distributed task.
*
*/
public interface DistributedTaskFailoverPolicy {
/**
* As parts of distributively executed task can fail due to the task itself throwing an exception
* or it can be an Infinispan system caused failure (e.g node failed or left cluster during task
* execution etc).
*
* @param failoverContext
* the FailoverContext of the failed execution
* @return result the Address of the Infinispan node selected for fail over execution
*/
Address failover(FailoverContext context);
/**
* Maximum number of fail over attempts permitted by this DistributedTaskFailoverPolicy
*
* @return max number of fail over attempts
*/
int maxFailoverAttempts();
}