org.gridgain.grid.kernal.processors.streamer.task

Class GridStreamerReduceTask<R1,R2>

java.lang.Object

org.gridgain.grid.compute.GridComputeTaskAdapter<T,R>

org.gridgain.grid.kernal.processors.closure.GridPeerDeployAwareTaskAdapter<Void,R2>

org.gridgain.grid.kernal.processors.streamer.task.GridStreamerReduceTask<R1,R2>

All Implemented Interfaces:

Serializable, GridComputeTask<Void,R2>, GridPeerDeployAware

@GridComputeTaskNoResultCache
public class GridStreamerReduceTask<R1,R2>
extends GridPeerDeployAwareTaskAdapter<Void,R2>

Streamer query task.

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
GridStreamerReduceTask(GridClosure<GridStreamerContext,R1> clos, GridReducer<R1,R2> rdc, String streamer)

Method Summary

Methods

Modifier and Type	Method and Description
Map<? extends GridComputeJob,GridNode>	map(List<GridNode> subgrid, Void arg) This method is called to map or split grid task into multiple grid jobs.
R2	reduce(List<GridComputeJobResult> results) Reduces (or aggregates) results received so far into one compound result to be returned to caller via GridComputeTaskFuture.get() method.
GridComputeJobResultPolicy	result(GridComputeJobResult res, List<GridComputeJobResult> rcvd) Default implementation which will wait for all jobs to complete before calling GridComputeTask.reduce(List) method.

Methods inherited from class org.gridgain.grid.kernal.processors.closure.GridPeerDeployAwareTaskAdapter

classLoader, deployClass

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

GridStreamerReduceTask

public GridStreamerReduceTask(GridClosure<GridStreamerContext,R1> clos,
                      GridReducer<R1,R2> rdc,
                      @Nullable
                      String streamer)

Parameters:

clos - Query closure.

rdc - Query reducer.

streamer - Streamer.

Method Detail

map

public Map<? extends GridComputeJob,GridNode> map(List<GridNode> subgrid,
                                         @Nullable
                                         Void arg)
                                           throws GridException

This method is called to map or split grid task into multiple grid jobs. This is the first method that gets called when task execution starts.

Parameters:

subgrid - Nodes available for this task execution. Note that order of nodes is guaranteed to be randomized by container. This ensures that every time you simply iterate through grid nodes, the order of nodes will be random which over time should result into all nodes being used equally.

arg - Task execution argument. Can be null. This is the same argument as the one passed into Grid#execute(...) methods.

Returns:

Map of grid jobs assigned to subgrid node. Unless GridComputeTaskContinuousMapper is injected into task, if null or empty map is returned, exception will be thrown.

Throws:

GridException - If mapping could not complete successfully. This exception will be thrown out of GridComputeTaskFuture.get() method.

reduce

public R2 reduce(List<GridComputeJobResult> results)
          throws GridException

Reduces (or aggregates) results received so far into one compound result to be returned to caller via GridComputeTaskFuture.get() method.

Note, that if some jobs did not succeed and could not be failed over then the list of results passed into this method will include the failed results. Otherwise, failed results will not be in the list.

Parameters:

results - Received results of broadcasted remote executions. Note that if task class has GridComputeTaskNoResultCache annotation, then this list will be empty.

Returns:

Grid job result constructed from results of remote executions.

Throws:

GridException - If reduction or results caused an error. This exception will be thrown out of GridComputeTaskFuture.get() method.

result

public GridComputeJobResultPolicy result(GridComputeJobResult res,
                                List<GridComputeJobResult> rcvd)
                                  throws GridException

Default implementation which will wait for all jobs to complete before calling GridComputeTask.reduce(List) method.

If remote job resulted in exception (GridComputeJobResult.getException() is not null), then GridComputeJobResultPolicy.FAILOVER policy will be returned if the exception is instance of GridTopologyException or GridComputeExecutionRejectedException, which means that remote node either failed or job execution was rejected before it got a chance to start. In all other cases the exception will be rethrown which will ultimately cause task to fail.

Specified by:

result in interface GridComputeTask<Void,R2>

Overrides:

result in class GridComputeTaskAdapter<Void,R2>

Parameters:

res - Received remote grid executable result.

rcvd - All previously received results.

Returns:

Result policy that dictates how to process further upcoming job results.

Throws:

GridException - If handling a job result caused an error effectively rejecting a failover. This exception will be thrown out of GridComputeTaskFuture.get() method.