org.apache.ignite.compute

Class ComputeTaskSplitAdapter<T,R>

java.lang.Object

org.apache.ignite.compute.ComputeTaskAdapter<T,R>

org.apache.ignite.compute.ComputeTaskSplitAdapter<T,R>

Type Parameters:

T - Type of the task execution argument.

R - Type of the task result returning from ComputeTask.reduce(List) method.

All Implemented Interfaces:

Serializable, ComputeTask<T,R>

Direct Known Subclasses:

GridifyTaskSplitAdapter

public abstract class ComputeTaskSplitAdapter<T,R>
extends ComputeTaskAdapter<T,R>

This class defines simplified adapter for ComputeTask. This adapter can be used when jobs can be randomly assigned to available grid nodes. This adapter is sufficient in most homogeneous environments where all nodes are equally suitable for executing grid job. See split(int, Object) method for more details.

Below is a coding example of how you would use ComputeTaskSplitAdapter:

 public class MyFooBarTask extends ComputeTaskSplitAdapter<Object, String> {
     @Override
     protected Collection<? extends ComputeJob> split(int gridSize, Object arg) throws IgniteCheckedException {
         List<MyFooBarJob> jobs = new ArrayList<MyFooBarJob>(gridSize);

         for (int i = 0; i < gridSize; i++) {
             jobs.add(new MyFooBarJob(arg));
         }

         // Node assignment via load balancer
         // happens automatically.
         return jobs;
     }

     // Aggregate results into one compound result.
     public String reduce(List<ComputeJobResult> results) throws IgniteCheckedException {
         // For the purpose of this example we simply
         // concatenate string representation of every
         // job result
         StringBuilder buf = new StringBuilder();

         for (ComputeJobResult res : results) {
             // Append string representation of result
             // returned by every job.
             buf.append(res.getData().string());
         }

         return buf.string();
     }
 }
 

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
ComputeTaskSplitAdapter()

Method Summary

Modifier and Type	Method and Description
Map<? extends ComputeJob,ClusterNode>	map(List<ClusterNode> subgrid, T arg) This method is called to map or split grid task into multiple grid jobs.
protected abstract Collection<? extends ComputeJob>	split(int gridSize, T arg) This is a simplified version of ComputeTask.map(List, Object) method.

Methods inherited from class org.apache.ignite.compute.ComputeTaskAdapter

result

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.apache.ignite.compute.ComputeTask

reduce

Constructor Detail

ComputeTaskSplitAdapter

public ComputeTaskSplitAdapter()

Method Detail

split

protected abstract Collection<? extends ComputeJob> split(int gridSize,
                                                          T arg)
                                                   throws IgniteException

This is a simplified version of ComputeTask.map(List, Object) method.

This method basically takes given argument and splits it into a collection of ComputeJob using provided grid size as indication of how many node are available. These jobs will be randomly mapped to available grid nodes. Note that if number of jobs is greater than number of grid nodes (i.e, grid size), the grid nodes will be reused and some jobs will end up on the same grid nodes.

Parameters:

gridSize - Number of available grid nodes. Note that returned number of jobs can be less, equal or greater than this grid size.

arg - Task execution argument. Can be null.

Returns:

Collection of grid jobs. These jobs will be randomly mapped to available grid nodes. Note that if number of jobs is greater than number of grid nodes (i.e, grid size), the grid nodes will be reused and some jobs will end up on the same grid nodes.

Throws:

IgniteException - Thrown in case of any errors.

See Also:

ComputeTask.map(List, Object)

map

public final Map<? extends ComputeJob,ClusterNode> map(List<ClusterNode> subgrid,
                                                       T arg)

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 ComputeTaskContinuousMapper is injected into task, if null or empty map is returned, exception will be thrown.