org.apache.ignite.compute

## Class ComputeTaskAdapter<T,R>

- java.lang.Object
- - org.apache.ignite.compute.ComputeTaskAdapter<T,R>

- Type Parameters:
    `T` - Type of the task argument.
    `R` - Type of the task result returning from `ComputeTask.reduce(List)` method.
  All Implemented Interfaces:
    Serializable, ComputeTask<T,R>
  Direct Known Subclasses:
    ComputeTaskSplitAdapter, GridifyDefaultRangeTask, GridifyDefaultTask, GridifyTaskAdapter

      public abstract class ComputeTaskAdapter<T,R>
      extends Object
      implements ComputeTask<T,R>

  Convenience adapter for `ComputeTask` interface. Here is an example of how `ComputeTaskAdapter` can be used:

       public class MyFooBarTask extends ComputeTaskAdapter<String, String> {
           // Inject load balancer.
           @LoadBalancerResource
           ComputeLoadBalancer balancer;

           // Map jobs to grid nodes.
           public Map<? extends ComputeJob, ClusterNode> map(List<ClusterNode> subgrid, String arg) throws IgniteCheckedException {
               Map<MyFooBarJob, ClusterNode> jobs = new HashMap<MyFooBarJob, ClusterNode>(subgrid.size());

               // In more complex cases, you can actually do
               // more complicated assignments of jobs to nodes.
               for (int i = 0; i < subgrid.size(); i++) {
                   // Pick the next best balanced node for the job.
                   jobs.put(new MyFooBarJob(arg), balancer.getBalancedNode())
               }

               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();
           }
       }

  For more information refer to `ComputeTask` documentation.
  See Also:
    Serialized Form

- - ### Constructor Summary

    Constructors
    Constructor and Description
    `ComputeTaskAdapter()`

  - ### Method Summary

    All Methods Instance Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `ComputeJobResultPolicy` | `result(ComputeJobResult res, List<ComputeJobResult> rcvd)` Default implementation which will wait for all jobs to complete before calling `ComputeTask.reduce(List)` method.

    - ### 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

      `map, reduce`

- - ### Constructor Detail

    - #### ComputeTaskAdapter

          public ComputeTaskAdapter()

  - ### Method Detail

    - #### result

          public ComputeJobResultPolicy result(ComputeJobResult res,
                                               List<ComputeJobResult> rcvd)
                                        throws IgniteException

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

      If remote job resulted in exception (`ComputeJobResult.getException()` is not `null`), then `ComputeJobResultPolicy.FAILOVER` policy will be returned if the exception is instance of `ClusterTopologyException` or `ComputeExecutionRejectedException`, 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 `ComputeTask<T,R>`
      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:
        `IgniteException` - If handling a job result caused an error effectively rejecting a failover. This exception will be thrown out of `ComputeTaskFuture.get()` method.

2022 Copyright © Apache Software Foundation
| Follow @ApacheIgnite
Ignite Database and Caching Platform | : ver. 2.12.0
Release Date | : January 10 2022